Impact Igniter Sport Peach Mango by ALLMAX

POSSIBLY EFFECTIVE

• Athletic performance. In some adults, taking beta-alanine appears to improve some, but not all, measures of athletic performance. Beta-alanine appears to work better for exercises that lasts at least 1 minute in duration; however, many other factors likely alter efficacy, such as the type of exercise, the subject's training experience, and the dosing regimen. Details: Many small clinical trials have evaluated the effects of beta-alanine supplementation in untrained individuals, recreational athletes, and professional athletes in a variety of sports and activities, including running, cycling, swimming, basketball, football, soccer, rowing, water polo, wrestling, weight lifting, skiing, and others. However, the results of individual trials are conflicting. Furthermore, studies have included multiple endpoints that have been both lab-based, such as time to exhaustion, strength endurance, time trials, and power output, and field-based, such as performance times (18227,94333,94334,94335,94336,94337,94338,94339,94340,94341)(94342,94343,94345,94346,94347,94348,94349,97956,97958,97960)(97962,97969,97970,97971,97972,101027,101028,101029,101030,104144)(104145,106710,106711,106713,106717,106718,112794). Meta-analyses of clinical trials show that taking beta-alanine 2-6.4 grams orally daily for 3-12 weeks provides minor improvements in exercise capacity and performance when compared with control (18227,94357,106717). In one meta-analysis, exercise capacity improved by an average of approximately 3% when compared with placebo (18227). However, meta-analyses suggest that improvements in exercise performance are less than exercise capacity (18227,94357). The majority of this research has only included males. Preliminary clinical research assessing the effect of beta-alanine on exercise capacity in females has not consistently demonstrated a benefit. However, the validity of these studies is limited by small sample sizes (14611,94338,94339,94345,97957,97967,104144,112791). Preliminary clinical research also suggests that beta-alanine is more effective for short exercises, lasting at least 1 minute. Longer exercises, lasting more than 10 minutes, have not been well studied. In addition, the type of athlete and type of exercise most likely to benefit from beta-alanine supplementation is unclear (18227,94357,106717). Pooled analyses have not identified the most effective dose of beta-alanine; however, preliminary subgroup analyses suggest that prolonged supplementation of at least 3-6 weeks may be needed to gain benefits (94357,106717). There does not seem to be a relationship between the daily beta-alanine dose and exercise-related outcomes, although one analysis suggests outcomes may be related to the total cumulative dose; most studies have used a total daily dose of 2.4-6.4 grams (18227,94357,101026,101027,101028,101029,101030,106712,106717). The majority of studies have evaluated various marketed formulations of beta-alanine (Carnosyn, Natural Alternatives International; Sustained Release Beta-Alanine, Musashi; Balance 100% unflavored pure beta-alanine, Vitaco Health; Intra X cell, Athletics Edge Nutrition) (94333,94335,94336,94337,94339,94342,94346,94347,94348,94349)(101028,101029,101030,104144,106710,106711,106718). Beta-alanine has also been studied in combination with 1 additional ingredient, namely sodium bicarbonate or creatine. Preliminary clinical research in physically active or trained males shows that taking beta-alanine 6-6.4 grams orally daily for 4-6 weeks with sodium bicarbonate 300-500 mg/kg orally daily for 1-7 days does not increase exercise capacity or exercise performance while cycling or sprinting when compared with individual supplementation (97959,97964,97966,101028). In contrast, preliminary clinical research in male athletes participating in martial arts or rowing shows that taking beta-alanine with sodium bicarbonate modestly increases exercise performance when compared with either ingredient taken alone (97962,97963). Other preliminary clinical research in healthy, untrained males shows that taking beta-alanine 1.6 grams daily for 28 days with creatine 5 grams twice daily for 22 days, followed by four times daily for 6 days, modestly increases power output during cycling when compared with placebo or taking either supplement alone (97973). In another very small clinical study in trained military males, taking beta-alanine 6.4 grams daily for 28 days with creatine 0.3 grams/kg daily for the last 7 days improves leg muscle power but not anaerobic power or muscle strength when compared with beta-alanine plus placebo (112793). Beta-alanine has also been studied in combination with multiple other ingredients. Preliminary clinical research shows that taking a specific product containing beta-alanine, creatine monohydrate, arginine, alpha-ketoisocaproate, and leucine (NO-Shotgun) or a different product containing beta-alanine, L-histidine, and carnosine (BETAFOR3MAX, Martinez Nieto S.A.) for 28 or 7 days, respectively, also improves strength and power output when compared with placebo (34451,106714). However, another very small crossover clinical study in healthy males shows that taking 6 mg/kg of a multi-ingredient pre-workout supplement containing beta-alanine, L-tyrosine, L-citrulline maleate, arginine alpha-ketoglutarate, L-taurine, and caffeine 30 minutes prior to weight training does not increase bench press strength endurance when compared with an equivalent amount of anhydrous caffeine (111250). It is unclear if these effects are due to beta-alanine, other ingredients, or the combination.
• Physical performance. Preliminary clinical research shows that taking beta-alanine improves exercise capacity and fatigue, but not strength or exercise performance, in older adults. Details: Clinical research in older adults shows that taking beta-alanine 2.4-3.2 grams daily for 4-12 weeks increases exercise capacity and delays fatigue during exercise when compared with placebo (16442,97955,97965). In addition, preliminary clinical research in older adults shows that taking an oral nutritional supplement fortified with beta-alanine 0.8-1.2 grams twice daily for 12 weeks increases exercise capacity when compared with taking the oral nutritional supplement alone (97961). Taking beta-alanine 2.4 grams daily also minimizes the reduction of executive functioning after cycling in older adults when compared with placebo (97955). However, 2 clinical studies in older adults show that taking beta-alanine (Natural Alternatives International) 2.4-3.2 grams daily for 10-12 weeks with or without an endurance-based resistance-training program does not improve strength, power, fatigue, or performance when compared with the resistance training program alone or placebo (101031,112792).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral beta-alanine is beneficial for cognitive decline in older adults. Details: A small clinical study in older adults shows that taking beta-alanine 1200 mg twice daily for 10 weeks reduces symptoms of depression and might improve cognitive function in subjects with borderline or low cognitive function at baseline when compared with placebo. However, beta-alanine supplementation does not improve cognitive function in older adults with normal cognitive function at baseline and does not benefit mood, anxiety, or executive function when compared with placebo (112792).
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral beta-alanine improves physical function in people with COPD. Details: A small clinical study in adults with COPD shows that taking beta-alanine (SR CarnoSyn, Natural Alternatives International, Inc) 800 mg four times daily for 12 weeks does not improve exercise capacity, muscle function, or physical activity when compared with placebo (112790).
• Cognitive function. Oral beta-alanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in trained military males shows that taking beta-alanine 6.4 grams daily for 28 days with creatine 0.3 grams/kg daily for the last 7 days modestly improves mathematical processing when compared to baseline, but not when compared with beta-alanine plus placebo. However, improvement from baseline was not found in the group taking beta-alanine plus placebo (112793).
• Exercise-induced muscle breakdown. It is unclear if oral beta-alanine improves muscle recovery after exercise. Details: Preliminary clinical research in untrained adults shows that taking beta-alanine 4.8 grams orally daily for 4 weeks does not improve muscle recovery after resistance exercises when compared with placebo (101026).
• Menopausal symptoms. Although there has been interest in using oral beta-alanine for menopausal symptoms, there is insufficient reliable information about the clinical effects of beta-alanine for this purpose.
• Obesity. It is unclear if oral beta-alanine improves body composition in adults. Details: A meta-analysis of several small clinical studies in active and sedentary adults shows that supplementing with beta-alanine 1.6-6.4 grams daily for 3-10 weeks does not reduce body mass, fat mass, body fat percentage, or free fat mass when compared with various controls. Subgroup analysis of dose, duration, and type of additional training did not change the results (112789).
• Sarcopenia. Although there has been interest in using oral beta-alanine for sarcopenia, there is insufficient reliable information about the clinical effects of beta-alanine for this purpose. More evidence is needed to rate beta-alanine for these uses.

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EFFECTIVE

• Migraine headache. Oral caffeine in combination with acetaminophen, aspirin, and/or sumatriptan is approved by the US Food and Drug Administration (FDA) for treating migraine headache. Details: Taking caffeine 100-260 mg orally in combination with acetaminophen 500-2000 mg, aspirin 500 mg, and/or sumatriptan 50-100 mg is effective for treating migraine headache (2715,2716,2717,37614,37626,37816,91068). Some evidence shows that caffeine in combination with aspirin and acetaminophen may be more effective than sumatriptan in treating a migraine attack (37666). However, taking caffeine 200 mg plus ergotamine seems to be less effective than sumatriptan or calcium carbasalate plus metoclopramide (37685,38312). Caffeine is an FDA-approved product for use with analgesics for the treatment of migraine.
• Neonatal apnea. Oral or intravenous caffeine citrate is approved by the US Food and Drug Administration (FDA) for the short-term treatment of neonatal apnea in very preterm infants. Details: Using caffeine orally or intravenously improves apnea of prematurity in very preterm infants and reduces the risk of bronchopulmonary dysplasia, invasive mechanical ventilation, and neurodevelopmental impairment (6023,6371,37857,37906,38124,38344,98807,100364,114658). The dosage approved in the FDA labeling is a single loading dose of caffeine citrate 20 mg/kg (10 mg/kg caffeine base), followed by 5 mg/kg of caffeine citrate (2.5 mg/kg caffeine base) every 24 hours for maintenance. Clinical research shows that caffeine citrate dose-dependently reduces the number of apnea episodes by at least 50% over 7-10 days of treatment (6371). Most research suggests that doses above 10 mg/kg daily reduce the risk of apnea, bronchopulmonary dysplasia, and problematic extubation when compared with doses below 10 mg/kg/day (98807,100364,114658). Additional clinical research shows that reinitiating caffeine treatment after termination of the original caffeine regimen, and continuing until 40 weeks postmenstrual age, reduces the incidence of intermittent hypoxia in premature infants by 46% when compared to standard care (91073). At 18-21 months of age, a history of neonatal caffeine treatment reduces the risk of long-term complications of apnea of prematurity, such as cerebral palsy or cognitive delay (37722,38340). At 11 years of age, individuals born prematurely and treated with caffeine have improved visuomotor, visuoperceptual, and visuospatial abilities when compared to those who received placebo (97452). At 6-11 years of age, these individuals may also have a reduced risk of motor impairment (114658). Data on the prophylactic use of caffeine in very low birth-weight infants (less than 1500 grams and 32 weeks' gestation) are conflicting. In a meta-analysis of 11 studies, 5 show a reduced risk of apnea of prematurity, oxygen therapy, bronchopulmonary dysplasia, patent ductus arteriosus, and retinopathy of prematurity, and a reduced duration of mechanical ventilation (111491). However, other studies do not show any benefit (38125,111491). A study of infants born at 34-36 weeks' gestation shows that caffeine citrate, 10 or 20 mg/kg orally daily, reduces the number of intermittent hypoxemia episodes per hour by 61% and 67% respectively, when compared with placebo (111493). Caffeine and aminophylline have similar effectiveness for management of apnea, bradycardia, and hypoxemia, but caffeine has a wider range of safe plasma levels and lower rates of tachycardia and feeding intolerance (111492).
• Postoperative headache. Oral or intravenous caffeine is approved by the US Food and Drug Administration (FDA) for preventing headache in postoperative patients who regularly consume caffeinated products. Details: Clinical research shows that using caffeine is effective for preventing postoperative headache in patients who regularly consume caffeinated products. Intravenous caffeine does not seem to be effective in non-regular caffeine consumers. Studied doses have included 200 mg intravenously or oral doses calculated based on average daily consumption (2725,2726). Caffeine is an FDA-approved product for preventing headache in postoperative patients who regularly consume caffeinated products.
• Tension headache. Oral caffeine in combination with analgesics is approved by the US Food and Drug Administration (FDA) for treating tension headache. Details: Taking caffeine orally in combination with analgesics is effective for treating simple tension headache. Taking caffeine 100 mg alone is more effective at reducing tension headache pain when compared with placebo, but less effective than the combination of caffeine and analgesics. Caffeine 130 mg has been used with acetaminophen 1000 mg or with acetaminophen 500 mg and aspirin 500 mg. Caffeine 50 mg has been used with acetylsalicylic acid 250 mg and acetaminophen 200 mg (2718,11832,37668,37773).

LIKELY EFFECTIVE

• Athletic performance. Oral caffeine taken as a single dose of at least 2-3 mg/kg can modestly improve endurance, muscle strength, power output, and overall athletic performance when taken prior to certain forms of athletic activity or exercise. However, the magnitude and duration of effect is variable and may be dependent on the form and dose of caffeine, as well as various individual- and activity-specific factors. Caffeine intake in excess of 800 mg daily can result in blood levels greater than those allowed by the National Collegiate Athletic Association. Details: Clinical research and meta-analyses of clinical research show that taking caffeine 2-10 mg/kg modestly improves work produced, aerobic endurance, muscle strength and endurance, power output, and overall athletic performance (10203,11832,37648,37894,38054,38063,95955,100362,100365,100371)(103701,103703,108798,111250,114655,114657,114661,114673). According to the International Society of Sports Nutrition, the most consistent and measurable effects are seen in aerobic endurance; the minimal effective dose for any form of exercise is unclear, but benefits have been most consistent at doses of 3-6 mg/kg (114673). Meta-analyses of studies using caffeine 3-9 mg/kg as a single dose prior to endurance time trials report variability in results. Sports studied included running, rowing, cycling, swimming, and Nordic skiing, and included both recreational and trained athletes. Overall there was a small positive effect on time to exhaustion, endurance performance, and mean power output, and a decrease in the time needed to complete the trials when compared with placebo (98808,111497,114655). One meta-analysis of studies that evaluated cycling time trial performance found that doses of 4-6 mg/kg, but not doses of 1-3 mg/kg, improved performance (114655). A separate meta-analysis of 14 clinical studies shows that taking caffeine 2-11 mg/kg approximately 45-60 minutes before exercise improves muscle strength and endurance in the upper and lower body when compared with placebo. However, a sub-group analysis shows that muscle strength only improves with caffeine doses of at least 6 mg/kg (114657). Another meta-analysis of small clinical trials shows that the benefit of caffeine on athletic performance seems to increase with increased duration of activity. This suggests that caffeine can improve physical endurance during athletic activities (100371). In these trials, caffeine is typically provided as a single dose 30-150 minutes prior to testing (98808), although one study suggests that taking caffeine 60 minutes prior to peak activity has the most consistent ergogenic benefits (104577). Caffeine might improve performance in some athletic activities but not others. Some research shows that caffeine does not improve performance during athletic activities requiring a high amount of exertion over a short period of time. Such activities include sprinting and lifting (11832,37564,37758,37837,37841,37890,38319,95963,97459,112740). However, it is possible that the negative lifting studies were underpowered. Ballistic exercise, such as jumping or throwing, requires rapid increases in velocity, force, and muscle activation. A meta-analysis of 10 studies shows that caffeine in a range of doses (mean: 3 mg/kg) has a significant ergogenic effect on throwing performance and velocity (111488). A meta-analysis of small studies shows that caffeine modestly improves bench press repetitions and maximum strength, but not perceived exertion, when compared with placebo. Caffeine also tends to improve these parameters for leg presses, but the improvement does not reach significance when compared with placebo (103701). A meta-analysis of small clinical studies in female team-sport athletes shows that caffeine improves specific team-sport skills but has no effect on perceived exertion or agility tests performed after exertion (108799). Conversely, a small individual clinical study shows that taking caffeine 6.5 mg/kg 60 minutes before strength training decreases perceived exertion while increasing the number of repetitions of both upper and lower limb exercises by 17% to 33% over placebo (104581). Some clinical research also shows that taking caffeine can decrease subjective feelings of exertion and fatigue during exercise such as fencing and cycling (17618,37656,91026,91058,91062). Although some other clinical studies show that caffeine does not affect perceived exertion, caffeine does seem to improve performance and cause small increases in the amount of physical work done when compared with placebo in various athletes, including cyclists, runners, basketball players, and golfers (37702,37860,37872,38031,38119,38320,91037,91077,97457,97459)(104580,108800,108804). These effects do not seem to be dependent upon the dose of caffeine (97459), although some research shows that the timing of caffeine intake and exercise may alter overall benefit, with a greater effect seen in the morning compared to the evening (97457,104580). Most research has investigated the acute effects of a single dose of caffeine. The evidence is mixed as to whether chronic intake of caffeine could induce tolerance and reduce any acute ergogenic benefits (114673). One study shows that the consistent consumption of caffeine 3 mg/kg daily for 28 days eliminates the acute benefits of caffeine in work produced when compared with placebo, suggesting the development of tolerance (95955). However, chronic use of caffeine at a dose of 6 mg/kg for 4 days does not seem to induce tolerance to an acute dose of caffeine 6 mg/kg taken 60 minutes prior to a cycling time trial in males who are moderate to high users of caffeine (104576). Similarly, a small clinical study in trained individuals shows that acute supplementation with oral caffeine 6 mg/kg about 1 hour prior to performance improves strength and endurance when compared with placebo or control, regardless of habitual caffeine consumption (108804). Differences may be due to the type of exercise, the acute dose of caffeine, the length of the chronic intake period, and/or the normal caffeine intake of the athlete. Most studies suggest that there is significant inter-individual variability in response to caffeine for improvement of athletic performance (100365). These differences might be due, at least in part, to genotype (100370,114673), although research is conflicting. Caffeine is metabolized by the cytochrome P450 1A2 (CYP1A2) enzyme. One small clinical trial in resistance-trained males shows that taking caffeine 6 mg/kg improves resistance exercise performance in those homozygous for the CYP1A2 rs762551 polymorphism (AA) when compared with those without or heterozygous for that polymorphism (CC or A/C, respectively) (100370). However, another clinical study in trained male athletes shows that taking oral caffeine 4 mg/kg about 30 minutes prior to performance decreases handgrip strength by about 13% in individuals with the CC genotype when compared with placebo, but not in those with the AA or A/C genotypes. No groups experienced an improvement in vertical jump performance (108803). Another small clinical study suggests that CYP1A2 genotype does not affect exercise performance in athletes 60 minutes after taking caffeine 3 mg/kg. In addition, the ADORA2A genotype, which plays a role in caffeine sensitivity, does not seem to affect exercise performance benefits from caffeine (104578). However, these studies are small and used different performance protocols; further research is needed to clarify how these polymorphisms may impact the athletic performance benefits of caffeine (114673). Limited research has also evaluated the use of a caffeine mouth rinse, with mixed findings. Two very small clinical studies in healthy trained males shows that rinsing the mouth with 25 mL of water containing caffeine 85 or 300 mg for 5-10 seconds does not affect athletic performance or time to exhaustion while cycling when compared with placebo (103709,108801). However, another small study in healthy Taekwondo athletes fasting for Ramadan suggests that using a mouth rinse containing caffeine 6 mg/kg, ten seconds prior to exertion, modestly reduces perceived exertion and modestly improves kick performance when compared with using a placebo rinse (103710). Similarly, another small clinical study in healthy, resistance-trained males shows that rinsing the mouth with 25 mL of a solution containing caffeine 3%, but not 1% or 2%, reduces perceived exertion and increases muscular endurance, but not strength, when compared with placebo. The mouth rinse was used for 5 seconds immediately prior to a strength test or once per minute for 2 minutes during a muscular endurance test (108802). Preliminary clinical research has also investigated the use of caffeine in combination with other ingredients, such as sodium bicarbonate or creatine. However these studies have not demonstrated clear benefits in athletic performance over taking caffeine alone (112740,114673).
• Mental alertness. Oral caffeine increases mental alertness. However, it might not improve performance or accuracy to the same extent achieved through adequate sleep. Details: Consumption of caffeinated beverages or caffeine supplements seems to prevent a decline in alertness and cognitive capacity when consumed throughout the day (4221,4224,36439,37727,37757,37759,38070,38075,38158,91093)(91075). Caffeine appears to be especially effective in individuals that are not regular users (91074). Taking caffeine 100-600 mg can improve alertness and speed following prolonged sleep deprivation but usually does not affect mental performance or accuracy (10205,37716,37755,37806,37992,38007,38035,38139,91049,91072)(103706,112736). Drinking coffee containing caffeine 100 mg prior to a cognitive performance test improves reaction times in people with recent poor sleep quality, and in those with adequate sleep. However, the increase in vigilance occurring in the sleep-deprived people does not bring their performance up to the level seen with adequate sleep. Also, the number of errors made by sleep-deprived people seems to increase, suggesting that caffeine may have a detrimental effect on inhibitory control (98809). Caffeine also appears to reduce cognitive impairment caused by medications such as chlorpheniramine (91058). Combining caffeine with certain other supplements may improve mental performance. Taking caffeine 80 mg with taurine seems to provide a small improvement in mental performance (9899), although this effect is not observed in sleep deprived subjects (38154). Some clinical research shows that combining caffeine 40-75 mg with glucose 37.5 grams or L-theanine 97-100 mg improves mental performance better than placebo or either substance alone (13732,37762,37903,38116); however, other clinical research shows no additional benefit from combining L-theanine and caffeine (91045).

POSSIBLY EFFECTIVE

• Bronchopulmonary dysplasia. Intravenous caffeine may reduce the risk for bronchopulmonary dysplasia in preterm infants. Details: Population research has found that initiating caffeine treatment prior to the third day of life in premature infants is associated with a reduced risk of developing bronchopulmonary dysplasia compared to later initiation of treatment with caffeine. Additionally, a meta-analysis of available clinical research shows that high-dose caffeine (40-80 mg/kg loading dose, 20 mg/kg daily maintenance) lowers the risk of bronchopulmonary dysplasia when compared with standard dosing (20 mg/kg loading dose, followed by 5-10 mg/kg daily maintenance). However, small sample sizes and high heterogeneity limit the validity of these findings (97462,100364).
• Diabetes. Dietary caffeine seems to be beneficial for the prevention of type 2 diabetes; it is unclear if it is beneficial for the prevention of gestational diabetes. Also, it is unclear if oral caffeine is beneficial in patients with type 1 or type 2 diabetes. Details: Total caffeine consumption from beverages such as coffee or tea is associated with a lower risk of developing type 2 diabetes. This effect appears to be dose-dependent (11353,14313,37850,37871,91040,100368). For example, an increase of 200 mg daily caffeine intake seems to be associated with a 14% decrease in the incidence of type 2 diabetes (91055). Additionally, in North American males, consuming caffeine 417 mg daily from coffee or tea is associated with a 20% lower risk of developing type 2 diabetes when compared with those consuming less than 37 mg daily. North American females consuming at least 258 mg of caffeine daily from coffee or tea seem to have a 10% to 30% lower risk of developing type 2 diabetes when compared with those consuming less than 140 mg daily (11353). Japanese adults who consume at least 416 mg of caffeine daily from beverages including coffee or green tea seem to have a 33% lower risk of developing type 2 diabetes compared to those who consume no more than 57 mg daily. The risk reduction appears to be more pronounced in Japanese females when compared with males (14313). It is unclear if caffeine is beneficial in adults with diabetes. A few small studies show that caffeine consumption may further reduce insulin sensitivity in patients with type 2 diabetes, gestational diabetes, or those at risk for developing diabetes (13744,37653,37820). Caffeine consumption has also been evaluated during pregnancy. An observational study has found that self-reported consumption of beverages containing up to 100 mg of caffeine at 16-22 weeks' gestation is associated with a 47% lower risk of developing gestational diabetes when compared with no intake (108814). Research regarding the effects of caffeine in patients with type 1 diabetes shows conflicting results. One study shows that taking caffeine 250 mg twice daily for 2 weeks can reduce the incidence of elevated blood sugar at night in patients with type 1 diabetes (37660). However, another study in patients with type 1 diabetes shows that taking caffeine 200 mg daily for 3 months may increase the ability to perceive hypoglycemic symptoms when compared with placebo, although overall glycemic control does not seem to be affected (6024). A small clinical crossover study evaluated caffeine for the prevention of exercise-induced hypoglycemia in adults with type 1 diabetes using ultra-long-acting insulin. This study shows that consuming a beverage containing caffeine 250 mg, glucose 10 grams, and aspartame 30 minutes before a moderate intensity cycling exercise does not reduce the risk of exercise-related hypoglycemia, alter the time to hypoglycemia, or increase peak plasma glucose levels during exercise when compared with taking glucose and aspartame (114662).
• Memory. Oral caffeine seems to be beneficial for short-term memory recall in college students and extroverted personalities. It is unclear if oral caffeine is beneficial for introverted personalities or other populations. Details: Taking a single dose of caffeine 65-200 mg orally daily seems to improve memory function in some individuals such as college students and people with extroverted personalities. A small study shows that taking caffeine does not improve memory function in individuals with introverted personalities (37845,38071,91080).
• Obesity. Oral caffeine, when taken in combination with ephedrine or as a component of green tea, seems to be beneficial for weight loss, short-term. Details: Taking caffeine orally, in combination with ephedrine or as a component of green tea, seems to help reduce weight, short-term (695,696,1704,8647,16892,37617,37831). Caffeine 192 mg in combination with ephedra 20-90 mg per day for 6 months seems to cause a modest weight reduction (5.3 kg) in people with a body mass index (BMI) between 25-40 kg/m². This combination, along with limiting fat intake to 30% of calories and moderate exercise, also seems to reduce body fat, decrease low-density lipoprotein (LDL) cholesterol, and increase high-density lipoprotein (HDL) cholesterol. However, even in carefully screened and monitored otherwise healthy adults, caffeine/ephedra combinations can cause small changes in blood pressure and heart rate (8647). Preliminary clinical research also shows that taking 1000 mg of a proprietary combination product containing caffeine and multiple other ingredients (Prograde Metabolism) twice daily for 8 weeks in conjunction with dieting reduces body weight, fat mass, waist circumference, and hip circumference by 1.5%, 5%, 1.8%, and 1.3%, respectively, when compared with dieting alone (40802).
• Pain (acute). Oral caffeine, when taken in combination with acetaminophen, propyphenazone, ibuprofen, or other pain-relieving agents, seems to be beneficial for acute pain. Details: Clinical research shows that taking caffeine 50-130 mg in combination with acetaminophen, propyphenazone, ibuprofen, or other pain-relieving agents can reduce acute pain when compared with the effects of pain-relieving agents alone (37587,37904,38036,38303,91038). Adding ≥100 mg caffeine to treatment with acetaminophen or ibuprofen results in 5% to 10% more patients that achieve at least 50% of maximum pain relief for over 4 hours when compared to treatment with acetaminophen or ibuprofen alone (91038).
• Postdural puncture headache. Oral or intravenous caffeine seem to be beneficial for preventing postdural puncture headache. Details: Using caffeine 300 mg orally or 500 mg in 1,000 mL normal saline intravenously seems to help treat and prevent postdural puncture headache (2727,2728). Using a combination of ergotamine and caffeine seems to be less effective than gabapentin for treating this condition (38147). Lower doses of oral caffeine may not be beneficial. Clinical research shows that oral caffeine, 75-125 mg, does not decrease the risk of postdural headache (91022).

POSSIBLY INEFFECTIVE

• Atrial fibrillation. Oral caffeine does not seem to prevent atrial fibrillation after cardiopulmonary bypass. In addition, it might increase the risk of gastrointestinal side effects. Details: In adults undergoing surgery with cardiopulmonary bypass, taking caffeine 400 mg every 8 hours for 6 doses does not seem to reduce the risk of developing atrial fibrillation during the first three post-operative days. This clinical study was stopped prior to the completion of recruitment after an interim analysis showed increased incidence of postoperative nausea and vomiting, and no effect on the incidence of atrial fibrillation (97451).
• Attention deficit-hyperactivity disorder (ADHD). Oral caffeine does not seem to reduce symptoms of ADHD in children. Details: Most research suggests caffeine does not significantly reduce ADHD symptoms in children when used at tolerable doses (10755,10756,10757,10758,10759,10760). The use of caffeine in adolescents and adults with ADHD has not been studied.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral caffeine prevents cognitive decline with aging. Details: Population research from a small cohort of elderly females shows that caffeine intake of more than 371 mg daily is associated with an attenuation in cognitive decline when compared to less than 30 mg daily. This is equivalent to the difference seen over a 7 year span of age. Caffeinated coffee consumption, but not caffeinated chocolate, tea, or cola, was associated with this attenuation in cognitive decline (91088).
• Alzheimer disease. It is unclear if oral caffeine is beneficial for preventing dementia; the available research is conflicting. Details: Population research from the UK Biobank has found that caffeine intake up to 400 mg daily is associated with a 24% to 34% reduced risk of developing Alzheimer disease when compared with lower intake. Conversely, population research from the Rush Memory and Aging Project in the US has found that caffeine intake of more than 100 mg daily is associated with a 41% increased risk of developing Alzheimer disease when compared with lower intake. However, when those with mild cognitive impairment at baseline or cases diagnosed within 2 years of follow-up are excluded, these findings become insignificant (108810).
• Asthma. Oral caffeine seems to modestly improve airway function for up to 4 hours in patients with mild to moderate asthma. However, it is unclear if oral caffeine has a clinically significant effect on asthma symptoms or quality of life. Details: Taking caffeine 9 mg/kg orally appears to modestly improve airway function for up to 4 hours in people with mild to moderate asthma (37907,37915). However, more research is needed to determine the appropriate dose, whether any benefit is clinically significant, or whether tolerance occurs with chronic dosing.
• Cancer pain. It is unclear if intravenous caffeine is beneficial for cancer pain. Details: Clinical research shows that receiving caffeine 200 mg intravenously once daily for 2 days results in a significant reduction in pain intensity by 0.833 points on the NRS scale when compared with control in patients receiving opioids for pain from advanced cancer (91081).
• Cognitive function. It is unclear if oral caffeine improves cognitive performance in trained athletes. Details: A meta-analysis of small studies in trained adult athletes shows that consumption of a low to moderate amount of caffeine 15-60 minutes prior to exercise and during exercise improves attention performance, but not reaction time or inhibitory control, when compared with placebo (108797). The validity of these findings is limited by unclear reporting.
• Dementia. It is unclear if oral caffeine is beneficial for preventing dementia or improving behavior in patients with dementia. Details: Population research from the Women's Health Initiative has found that caffeine intake of more than 175 mg daily is associated with a 26% reduced risk of developing probable dementia or global cognitive impairment when compared to less than 175 mg daily in postmenopausal adults 65-80 years of age (97458). Population research from the UK Biobank has found that caffeine intake up to 400 mg daily is associated with a 17% to 26% reduced risk for developing all-cause dementia when compared with lower intake. Conversely, population research from the Rush Memory and Aging Project in the US has found that caffeine intake of more than 100 mg daily is associated with a 35% increased risk of developing all-cause dementia when compared with lower intake. However, when those with mild cognitive impairment at baseline or cases diagnosed within 2 years of follow-up are excluded, these findings become insignificant (108810). Caffeine consumption has also been evaluated in patients with dementia. A cross-sectional study in patients with dementia in a care home has found that intake of 'normal' to 'high' amounts of caffeine are associated with reduced agitation and other behavioral symptoms when compared to 'low' intakes of caffeine (104574).
• Depression. It is unclear if oral caffeine is beneficial for depression prevention. Details: Some population research found that caffeine intake is associated with an increased incidence of depressive symptoms in pediatric patients (37839,38162). However, other population research found that caffeinated beverage intake is associated with a decreased incidence of depression in adults (37969,38165,91067,100366).
• Electroconvulsive therapy (ECT) augmentation. Although there has been interest in using intravenous caffeine sodium benzoate to augment electroconvulsive therapy, there is insufficient reliable information about the clinical effects of caffeine for this condition.
• Exercise-induced hypoxemia. It is unclear if oral caffeine is beneficial for hypoxemia associated with exercise. Details: Preliminary clinical research in athletes experiencing exercise-induced hypoxemia shows that taking caffeine 8 mg/kg can improve exercise ventilation, but not ventilatory response or oxygen saturation, when compared with placebo (37750).
• Exercise-induced muscle soreness. It is unclear if oral caffeine is beneficial for reducing muscle soreness during exercise. Details: There is conflicting clinical evidence as to whether caffeine can reduce exercise-induced muscle pain. Some evidence shows that taking caffeine 100 mg or 10 mg/kg can reduce muscle pain during exercise when compared with placebo (37622,38146). However, the effect of lower doses is unclear. Some evidence shows that taking caffeine 5 mg/kg may reduce exercise-induced muscle pain when compared with placebo (37747,91050), while other evidence suggests that taking caffeine 2-5 mg/kg does not affect muscle pain during exercise (38141).
• Gallbladder disease. It is unclear if increased dietary caffeine intake reduces the risk of developing gallstones. Details: Consumption of caffeinated beverages that provide 400 mg or greater of caffeine per day is associated with a significantly reduced risk of developing symptomatic gallstone disease (3345,8032). The effect seems to be dose-dependent; consumption of 800 mg caffeine per day has the greatest reduction in risk (3345).
• Hepatitis C. It is unclear if increased dietary caffeine reduces the risk for hepatitis C-associated severe liver inflammation, although it may reduce the risk of developing advanced fibrosis. Details: A meta-analysis of population research has found that regular consumption of caffeine at doses of at least 123 mg daily is associated with a 48% reduced risk of advanced liver fibrosis when compared to lower caffeine intake in patients with hepatitis C virus (95947). An individual population study also found that higher intake of caffeine from coffee is associated with reduced severity of liver fibrosis in patients with chronic hepatitis C virus. For these patients, the risk of advanced fibrosis is reduced by 14% for each 67 mg of caffeine (37896). However, caffeine intake does not appear to be associated with a reduced risk of moderate to severe liver inflammation in patients with hepatitis C (95947).
• Hypnic headache. It is unclear if oral caffeine reduces the pain associated with this rare condition. Details: Anecdotal evidence suggests that drinking a cup of coffee containing caffeine before bed or upon waking up may help alleviate pain associated with hypnic headaches (38078).
• Hypotension. It is unclear if oral caffeine is beneficial in people with low blood pressure. Details: Preliminary clinical research shows that consuming caffeinated beverages increase blood pressure in elderly people with postprandial hypotension (11834,11835).
• Intermittent claudication. It is unclear if oral caffeine is beneficial for intermittent claudication. Details: Taking a single dose of caffeine 6 mg/kg orally seems to improve walking distance, muscular strength, and endurance in patients with intermittent claudication; however, balance seems to be reduced (38038).
• Liver disease. It is unclear if oral caffeine is beneficial for liver disease prevention. Details: Population research found that there is an inverse association between intake of coffee and the incidence of liver cirrhosis (37576,37608). However, it is unclear if this effect of coffee is attributable to caffeine, since other caffeinated beverages do not show this effect.
• Multiple sclerosis (MS). It is unclear if oral caffeine is beneficial for the symptoms of multiple sclerosis (MS). Details: A small crossover study in adults with MS shows that taking caffeine 200 mg daily for 12 weeks may modestly improve balance, functional mobility, and MS-related quality of life, but not walking function, when compared to a 2-week placebo run-in period. All patients were told to eliminate all other forms of caffeine from their diets; however, baseline caffeine intake was not recorded (114663). The validity of this study is limited by the small size and heterogeneous nature of the study population, which included patients with various forms of MS at varying levels of severity.
• Narcolepsy. It is unclear if oral caffeine is beneficial for narcolepsy. Details: A small clinical study in patients with narcolepsy shows that taking caffeine 200 mg daily in the morning for 1 week does not affect reaction time, but modestly reduces drowsiness, when compared with baseline (103698). The validity of this finding is limited by the lack of a statistical comparison between the treatment and placebo groups.
• Neonatal resuscitation. It is unclear if oral caffeine improves the likelihood for successful extubation in preterm infants. Details: Preliminary clinical research in extremely preterm infants requiring mechanical ventilation within the first 5 days of birth shows that early administration of caffeine, given as a loading dose of caffeine citrate 20 mg/kg followed by a maintenance dose of 5 mg/kg daily until extubation, does not reduce mortality or shorten time to first successful extubation when compared to giving a bolus dose of caffeine citrate 20 mg/kg just prior to extubation (97461).
• Nocturnal enuresis. Reducing caffeine intake might reduce the frequency of nocturnal enuresis episodes in children. Details: Preliminary clinical research in children aged 6-15 years with primary nocturnal enuresis shows that limiting caffeine intake to less than 30 mg daily reduces the mean number of bedwetting episodes from 3.5 to 2.4 per week, when compared with no change in the group with intakes of 80-100 mg daily. The probability of bedwetting in the caffeine restricted group was about 14% lower than that in the control group (111495).
• Nonmelanoma skin cancer. It is unclear if oral caffeine is beneficial for nonmelanoma skin cancer prevention. Details: A review of available population research shows that increased caffeine intake from any source is associated with a 14% reduction in the risk of developing nonmelanoma skin cancer. Consumption of caffeinated coffee, but not decaffeinated coffee, is associated with an 18% reduced risk (97465).
• Parkinson disease. Although consuming caffeinated beverages might reduce the risk of developing Parkinson disease, it is unclear if oral caffeine is beneficial for improving symptoms. Also, oral caffeine does not seem to prevent tardive dyskinesia. Details: It is unclear whether caffeine improves some symptoms of Parkinson disease, as results from clinical research are conflicting (91069,95951,95954,103705). One clinical study in Parkinson disease patients with extreme daytime somnolence shows that taking caffeine 100 mg twice daily for 3 weeks and then 200 mg twice daily for 3 weeks results in modest improvements in rigidity and bradykinesia, but inconsistent improvements in drowsiness, when compared with placebo (91069). Other clinical research shows that caffeine 200 mg twice daily does not lead to improvements in motor severity, cognition, or somnolence after 6, 12, or 18 months when compared with placebo (95954). Furthermore, a large retrospective study has found that caffeine consumption of more than 300 mg daily for 18 months in conjunction with dopaminergic therapy does not slow the rate of Parkinson disease progression. This research also shows that a reported consumption of caffeine greater than 300 mg, in conjunction with creatine 10 grams daily for 18 months, may accelerate the rate of Parkinson disease progression (95951). The retrospective nature of this study limits the validity of these findings. Caffeine does not appear to be helpful for reducing the risk of tardive dyskinesia. A retrospective analysis has found no definitive difference in onset of tardive dyskinesia in Parkinson patients consuming more than 204 mg caffeine daily when compared with those consuming less than 68 mg daily (91090). Despite these mainly negative findings, large-scale epidemiological studies have found that people who consume caffeinated beverages, such as coffee, tea, and cola, have a decreased risk of Parkinson disease (37931,91060,91071,103705). Males consuming 3-4 cups (28 oz) of caffeinated coffee per day, or 421-2716 mg total caffeine, seem to have the lowest risk of developing this condition. However, a lower risk is also associated with consumption of as little as 124-208 mg of caffeine (6022). In females, more moderate caffeinated coffee consumption, such as 1-3 cups per day, seems to be best (1238). Caffeine does not appear to provide additional protection from Parkinson disease in cigarette smokers (9236,91060).
• Postoperative ileus. It is unclear if oral caffeine is beneficial for improving bowel recovery following colorectal surgery. Research is conflicting and may vary depending on the type of procedure performed. Details: A meta-analysis of two small clinical trials in adults undergoing elective laparoscopic colorectal resection shows that taking caffeine 100-200 mg three times daily, starting on postoperative day 1, does not reduce the time to the first stool, time to first flatus, or length of hospital stay (LOS) when compared with placebo (112732). Another meta-analysis of 8 trials, including the 2 trials discussed previously, pooled 610 patients undergoing open and laparoscopic colorectal procedures. The analysis shows that caffeine taken three times daily, starting either on the day of surgery or on postoperative day 1, reduces LOS and the time to first bowel movement when compared with placebo, tea, or decaffeinated coffee. However, a sub-analysis of only laparoscopic procedures shows no difference in LOS between groups. These findings are limited by high heterogeneity, which appears to be due primarily to differences between open and laparoscopic procedures (114660).
• Postoperative pain. It is unclear if intravenous caffeine is beneficial for reducing opioid consumption in adults undergoing surgery. Details: A small clinical study in adults undergoing laparoscopic colorectal and gastrointestinal surgery shows that intravenous caffeine citrate 200 mg at the initiation of surgical closure has no effect on cumulative opioid consumption through postoperative day 3 when compared with placebo. In fact, post-hoc analysis with adjustment for age, sex, comorbidities, history of anxiety or depression, and open surgical conversion suggests an increase in opioid consumption with administration of caffeine when compared with placebo (108809).
• Pre-eclampsia. It is unclear if oral caffeine intake affects the risk of gestational hypertension or pre-eclampsia. Details: a meta-analysis of 10 observational studies including about 115,000 pregnant people did not find an association between the level of caffeine intake during pregnancy and the risk of developing gestational hypertension or pre-eclampsia (111485).
• Stroke. It is unclear if oral caffeine is beneficial for stroke prevention. Details: Population research has found that increased intake of either caffeinated or decaffeinated coffee is associated with a decreased risk of stroke in females (37804). However, it is not clear if the effect of coffee is attributable to the caffeine component.
• Tinnitus. It is unclear if oral caffeine is beneficial in patients with chronic tinnitus. Details: A small clinical study in adults with chronic tinnitus shows that taking a single dose of caffeine 300 mg improves mood and quality of life at 1 hour when compared with baseline. (108805). The lack of statistical comparison to the placebo group limits the validity of these findings. More evidence is needed to rate the effectiveness of caffeine for these uses.

(Read more about CAFFEINE)

EFFECTIVE

• Dyspepsia. Oral calcium carbonate is approved by the US Food and Drug Administration (FDA) as an antacid. Details: Taking calcium carbonate orally as an antacid is effective for treating dyspepsia (1843). Calcium carbonate has FDA approval as an antacid.
• Hyperkalemia. Intravenous calcium gluconate is approved by the US Food and Drug Administration (FDA) for preventing hyperkalemia-induced cardiac abnormalities. Details: Administering calcium gluconate intravenously can reverse electrocardiographic changes and arrhythmias induced by hyperkalemia (12946). Intravenous calcium gluconate is FDA-approved for preventing hyperkalemia-induced cardiac abnormalities.
• Hypocalcemia. Oral calcium treats and prevents hypocalcemia. Intravenous calcium is used to treat severe hypocalcemia. Details: Taking calcium orally is effective for treating and preventing hypocalcemia. Intravenous calcium gluconate, acetate, gluceptate, or chloride is effective for severe hypocalcemia or hypocalcemic tetany (12928).
• Kidney failure. Oral calcium carbonate or calcium acetate is used as a phosphate binder during kidney failure. Details: Taking calcium carbonate or calcium acetate orally is effective as a phosphate binder. Calcium acetate (PhosLo) appears to control hyperphosphatemia better than sevelamer (Renagel) (12943,12944,38990). Calcium citrate is not recommended for this purpose because it increases aluminum absorption and does not bind phosphate as efficiently as calcium acetate or calcium carbonate (21631). Some clinical research also shows that taking calcium orally reduces blood pressure in patients with kidney failure (975).

LIKELY EFFECTIVE

• Corticosteroid-induced osteoporosis. Oral calcium in combination with vitamin D prevents bone density loss that occurs during long-term treatment with corticosteroids. Details: Taking calcium in combination with vitamin D as adjunctive therapy seems to be effective for reducing bone mineral density loss in people using corticosteroids long-term (982,1046,1830,1831,1832,4462,4463,4464,4465,4466)(4467,12945,38493). One specific product used in clinical research is Oscal (Marion Merrel Dow Inc.), which contains elemental calcium 500 mg per tablet plus vitamin D 125 IU per tablet (982). Another product used is Oscal 250 + D (SmithKline Beecham Healthcare), which contains elemental calcium 250 mg and vitamin D 125 IU per tablet (1046).
• Hyperparathyroidism. Oral calcium reduces parathyroid hormone levels in patients with secondary hyperparathyroidism due to kidney failure. Details: Taking calcium orally reduces parathyroid hormone levels in patients with kidney failure and secondary hyperparathyroidism (1827,1828,1829,39174,39425). In elderly women, the combination of calcium and vitamin D reverses secondary hyperparathyroidism and reduces hip fracture risk (8818). Also, population research suggests increased calcium intake from the diet and supplements reduces the risk of primary hyperparathyroidism in women. Supplemental intakes of at least 500 mg/day and dietary intakes of approximately 1100 mg/day are considered to be protective (91353).
• Osteoporosis. Adequate calcium intake, from the diet and/or supplements, is recommended for the prevention and treatment of osteoporosis. Details: The Bone Health and Osteoporosis Foundation (BHOF) recommends ensuring adequate calcium intake in line with the recommended dietary allowance (RDA) by age, along with adequate vitamin D intake, for the prevention and treatment of osteoporosis in adults over 50 years of age. Supplementation can be used to augment dietary intake when adequate dietary intake is not feasible (109425). In the US and Canada, foods containing at least 200 mg calcium with less phosphorous content than calcium can be labelled with a health claim regarding the relationship between adequate calcium intake and a reduced risk for osteoporosis (11940,102148). However, calcium supplementation is not recommended specifically for the primary prevention of osteoporosis. The US Preventive Task Force (USPSTF) states that the current evidence is insufficient to assess the balance of benefits and harms of vitamin D and calcium supplementation, alone or in combination, for the primary prevention of fractures in community dwelling adults without osteoporosis (95695). Also, calcium supplements do not seem to be effective for preventing loss of bone mineral density (BMD) during lactation (988), in patients who have had bone marrow transplantation (1817), or in patients who have had renal transplantation (4823,38736,38871). Maximal bone growth occurs in the teenage years, and then BMD in females remains relatively constant until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In males, this occurs several decades later. Bone loss is more pronounced if dietary calcium intake is below the RDA, which is the case for many Americans (2571,2578). One meta-analysis of randomized controlled trials in healthy children 7-14 years old shows that fortifying food with calcium 250-1000 mg daily for up to 24 months modestly improves femoral neck BMD, but not hip or spine BMD. However, the included trials did not supplement vitamin D (107232). During the 5 years immediately after menopause, calcium supplementation has very little effect on bone loss (2569,2570,2575,2576). The rapid loss of estrogen causes a high bone resorption rate, which increases serum calcium levels and therefore decreases intestinal absorption of calcium (2570). After this period, the typical rate of bone loss is 2% per year (2572,2576). Taking calcium 1000-1600 mg daily as carbonate, citrate, lactate gluconate, or citrate malate salt decreases this rate by 0.25% to 1% annually (977,979,981,2569,2571,2572,2575,2576,2578,6850)(38978,38980,39064). The greatest reductions (1% or more) are seen in the first 1-2 years of supplementation when bone remodeling foci can be filled (2569,2576). After this period, the differences in rate of loss between supplemented and non-supplemented females are closer to 0.25% per year (2569,2577). A meta-analysis of clinical evidence suggests that there is no additional benefit after 4 years (38980). Small clinical studies have found that continuous calcium supplementation at an average daily dose of 1050 mg, started after menopause and continued for 1.5-4 years, may reduce fracture rates by 26% when compared with no calcium supplementation. The largest of these studies was conducted in nursing home residents who also received daily vitamin D; the benefits of calcium, specifically, are unclear (39386). Some research also suggests that calcium and vitamin D improves primary prevention of osteoporotic fractures in some older individuals with osteoporosis, particularly the elderly and those who are no longer community dwelling (12930,38875,38849,39026,109471). However, not all research is positive. One large clinical trial in elderly adults with a low-trauma fracture show that taking calcium 1000 mg daily with or without vitamin D 800 IU daily for 2-7 years does not reduce the risk of a second fracture when compared with placebo (13073). Another clinical study shows that taking calcium 1000 mg daily plus vitamin D 800 IU daily does not prevent a second fracture in elderly patients, or prevent a first fracture in elderly patients with other risk factors such as low body weight (less than 58 kg, 127.6 pounds), smoking, family history of hip fracture, or fair or poor self-reported health (12929). Also, some exploratory research suggests that supplements may need to be continued indefinitely; in adults over 68 years of age, any effects of 2 years of calcium supplements on BMD appear to be lost within 2 years after discontinuing supplements (6853). Calcium has additive effects when used with other agents such as vitamin D, estrogens, or calcitonin. Whereas calcium alone generally reduces or prevents loss of BMD, combination with other agents can produce small increases in BMD ranging from 0.3% to 3.3% depending on the combination and dosages used (978,980,1836,2570,2571,2572,2576). However, one meta-analysis in healthy adults shows that fortifying foods with calcium 250-1000 mg daily, in conjunction with vitamin D supplementation, for up to 24 months does not improve BMD when compared with control (107232). The full potential of osteoporosis treatments cannot be realized without adequate calcium intake (2569,2570,2571,2572). Advise patients taking agents such as estrogens, calcitonin, bisphosphonates, or raloxifene (Evista) to ensure that their daily calcium intake meets the RDA. Use supplements if necessary. The usefulness of calcium in preventing osteoporosis in males is not as well-studied. Some observational research has found that calcium 870 mg daily is not associated with changes in BMD and bone loss in males (97201). However, clinical evidence suggests that taking calcium 1000 mg daily for 2 years might improve trabecular or cortical bone mass by 2% to 4% (980,8827,8873). Dietary supplementation with calcium and vitamin D seems to moderately reduce bone loss measured in the femoral neck, spine, and total body, and seems to reduce the incidence of nonvertebral fractures in older patients with osteopenia or low BMD (980).
• Premenstrual syndrome (PMS). Adequate calcium intake seems to prevent symptoms of PMS. Details: There seems to be a link between low dietary calcium intake and symptoms of PMS (2004,6847,39007). Taking calcium 1000-1336 mg daily seems to significantly reduce depressed mood, water retention, and pain, especially if daily calcium intake is inadequate (1822,1823,1824,2004,95821). Calcium carbonate 1200 mg daily seems to decrease PMS symptom scores by about 18% when compared with placebo (1822). Increasing dietary calcium intake is also associated with a decreased risk of developing PMS. Consuming an average of 1283 mg of calcium per day from foods is associated with about a 30% lower risk of developing PMS compared with consuming an average of 529 mg daily (13094); however, taking calcium supplements does not appear to be associated with the risk of developing PMS.

POSSIBLY EFFECTIVE

• Colorectal cancer. Oral calcium seems to be beneficial for preventing colorectal cancer, especially in those with adequate vitamin D levels and normal body mass index (BMI). Details: Population studies have found that increased intake of dietary or supplemental calcium is associated with a reduced risk of colorectal cancer and colorectal adenomas (1047,8820,12120,38951,98898,98899). Clinical trials and meta-analyses of clinical research also show that taking calcium supplements 1.2-2 grams daily for up to 4 years can reduce the risk of colorectal adenoma recurrence by up to 29% (970,12118,12950,15267,34596,38718,39042,95817). However, not all research has been positive. Some meta-analyses of clinical research or observational studies suggest that taking calcium does not reduce the risk of familial adenomatous polyposis or colorectal cancer (34596,39042,39349). Other contradictory research suggests that postmenopausal females who take calcium 1000 mg daily plus vitamin D 400 IU daily do not have a reduced risk of developing colorectal cancer (14290); however, this finding may not be reliable due to the high baseline intake of calcium in study participants. The reason for these conflicting findings is not entirely clear. Vitamin D might be an important factor. People with lower than average vitamin D levels do not seem to get any benefit from calcium supplements (12118). Also, one meta-analysis of previous trials suggests that taking calcium 1200 mg daily reduces the risk of colorectal adenomas in people with a normal BMI, but not in those who are overweight or obese (99715). Despite this conflicting evidence, the US Food and Drug Administration (FDA) approved a qualified health claim in 2005 stating that calcium supplements may reduce the risk of colorectal cancer and colorectal adenomas. However, the FDA has determined that there is little scientific evidence to support this claim (102366).
• Fetal bone mineralization. If calcium intakes are low during pregnancy, oral calcium seems to be beneficial for increasing fetal bone density. Details: With low dietary calcium intake (less than 562 mg elemental calcium daily) during pregnancy, calcium supplementation increases fetal bone mineralization and density. However, calcium supplementation does not offer any additional benefit if calcium intakes are adequate (3263,3264).
• Hypertension. Oral calcium seems to reduce blood pressure by a small amount in adults with or without hypertension. However, it is unclear if this reduction is clinically significant. Details: Many clinical trials and observational studies, including a meta-analysis of 18 high-quality clinical trials, show that intake of calcium supplements or dietary calcium modestly reduces systolic blood pressure in patients with or without hypertension, usually around 1-2 mmHg. Calcium seems to be more effective for certain subpopulations of patients, such as those who are salt-sensitive or have low baseline dietary calcium intake (945,972,974,976,984,1818,1819,1820,1821,6852)(13138,14406,38803,39063,39094,39221,113920,113925). However, a large-scale clinical trial in postmenopausal females shows that taking vitamin D (cholecalciferol) 400 IU daily in combination with elemental calcium 1000 mg daily does not lower blood pressure or reduce the risk of developing hypertension (16714). Additionally, a meta-analysis of 8 clinical trials shows that taking calcium in combination with vitamin D for up to 7 years has no effect on blood pressure (98861). The validity of this finding is limited by the poor methodological quality of the included studies. Some observational research suggests that calcium can reduce the risk for hypertension. Population research in females aged 45 years and older suggests that higher intake of calcium from both diet and supplemental sources is linked to a lower risk of developing hypertension when compared to lower calcium intake (14265). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim stating that calcium supplements may reduce the risk of hypertension. However, the FDA has concluded that this claim is based on supporting, rather than conclusive, evidence (102367). Research evaluating the effect of calcium supplementation during pregnancy on the child's blood pressure has yielded conflicting findings. A systematic review of 2 clinical studies and 3 observational studies found that calcium intake during pregnancy is associated with a 1-2 mmHg reduction in the systolic blood pressure of the offspring between the ages of 1-7 years (38852). However, a separate meta-analysis of 3 clinical studies shows that calcium intake during pregnancy does not reduce systolic or diastolic blood pressure in the offspring (113923).
• Osteomalacia. Oral calcium seems to reverse osteomalacia caused by very low calcium intakes. Details: Osteomalacia is commonly caused by vitamin D deficiency; however, very low calcium intake can also lead to osteomalacia in children and adults. Calcium supplementation can reverse osteomalacia caused by calcium deficiency. Along with appropriate vitamin D supplementation, individuals at risk of osteomalacia need sufficient calcium intake (94819).
• Pre-eclampsia. Oral calcium seems to reduce the risk of pre-eclampsia, especially in high-risk individuals and those with low baseline dietary calcium intake. Details: Although there is some conflicting evidence (971,38756), most clinical research shows that taking calcium orally 1-2 grams daily reduces the risk of pre-eclampsia (973,1833,8828,39043,39319,39426,97348,113919). A large clinical trial of 11,000 pregnant individuals in India and Tanzania shows that supplementation with 500 mg daily is similarly effective to 1500 mg daily (113908). Multiple meta-analyses which include 16-30 clinical studies have found that varying doses of calcium supplementation reduce the relative risk of pre-eclampsia by 46% to 51% when compared with placebo (97348,113909,113919). One of these meta-analyses found that for every 19 females treated with calcium, one episode of pre-eclampsia would be avoided (97348). Additionally, one of these meta-analyses found that calcium reduces the relative risk of pre-eclampsia by 51%, regardless of whether it is taken at a dose above or below 1000 mg daily (113919). Some research suggests that calcium supplementation may have a greater effect in individuals at high risk of pre-eclampsia or with low baseline dietary calcium intake, and when taken at greater than or equal to 20 weeks of gestation (15029,38497,97348,99714,113919). However, another meta-analysis of 30 clinical studies found a similar benefit of calcium in both high- and low-risk individuals (113919). A separate meta-analysis of 6 clinical studies conducted in China evaluated the benefits of calcium carbonate 500-600 mg daily taken in conjunction with aspirin 50-75 mg daily during pregnancy. This combination was associated with an 80% lower relative risk of pre-eclampsia and an 83% lower relative risk of pre-eclampsia with gestational hypertension when compared with routine care (113913). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim regarding the use of calcium supplements to reduce the risk of pregnancy-induced hypertension and pre-eclampsia. However, due to the limited and conflicting research available at that time, the FDA stated that this outcome was highly unlikely (102366). Since then, large, high-quality clinical research has supported this finding. In fact, in 2016 the World Health Organization (WHO) released a recommendation to prescribe oral calcium 1.5-2 grams daily during pregnancies at high risk of pre-eclampsia if dietary calcium intakes are low (97347).
• Pregnancy-induced hypertension. Oral calcium may reduce the risk of pregnancy-induced hypertension. Details: A meta-analysis of 17 clinical studies shows that calcium supplementation during pregnancy may reduce the relative risk of pregnancy-induced hypertension by 30% when compared with control (113909). A separate meta-analysis of 6 clinical studies conducted in China, which evaluated the benefits of calcium carbonate 500-600 mg daily taken in conjunction with aspirin 50-75 mg daily during pregnancy, shows that this combination reduces the relative risk of pregnancy-induced hypertension by 85% when compared with routine care (113913).
• Rickets. Oral calcium seems to reverse rickets caused by very low calcium intakes. Details: Rickets is commonly caused be vitamin D deficiency; however, very low calcium intake can also lead to rickets. Calcium supplementation can reverse rickets caused by calcium deficiency (94819). A small clinical study in children with nutritional rickets shows that taking calcium 500-2000 mg daily for 24 weeks improves radiographically measured rickets caused by calcium deficiency. Rickets seems to improve more rapidly with calcium 1000 mg compared to calcium 500 mg. However, increasing the calcium dose to 2000 mg daily is not more beneficial than calcium 1000 mg daily (98904).
• Tooth retention. Oral calcium with vitamin D seems to help with tooth retention in the elderly population. Details: A clinical trial in the elderly population shows that taking calcium citrate malate 500 mg daily along with vitamin D3 (cholecalciferol) 700 IU daily orally for 3 years reduces the risk of tooth loss by about 52% when compared with placebo (8816).

POSSIBLY INEFFECTIVE

• Breast cancer. Oral calcium, via supplementation or as part of the diet, does not seem to be beneficial for breast cancer prevention. Details: Although some studies disagree (15631,39041,95811,107237,113917), most population research suggests that increased calcium intake is not associated with overall breast cancer risk (15631,16715,98895,107236,107237,113917). However, one meta-analysis of observational studies shows that although higher total calcium intake is not associated with breast cancer risk, higher dietary calcium intake, specifically, may be associated with a slightly reduced risk (113917). Also, some analyses suggest that calcium intake may be associated with the risk for certain breast cancer sub-types. Some subgroup analyses suggest that calcium intake may reduce the risk of breast cancer in postmenopausal, but not pre-menopausal, adults (15631,107237) and that dietary calcium intake may reduce estrogen receptor(ER)-negative breast cancer, but not ER-positive breast cancer (107236). However, most research has not evaluated the effects of calcium supplementation or intake on breast cancer subtypes. The best evidence to date, from a large scale clinical trial (Women's Health Initiative), shows that taking vitamin D (cholecalciferol) 400 IU daily plus calcium 1000 mg daily for 7 years after menopause does not reduce the risk of developing invasive breast cancer at the end of the study and 5 years after the end of the intervention (16715,98895).
• Fractures. Although oral calcium prevents fractures in osteoporosis, most evidence shows that calcium does NOT prevent factures in people who do not have osteoporosis. See Osteoporosis discussion for more information on the use of calcium for this purpose. Details: Robust meta-analyses of mostly large, high-quality clinical studies show that calcium supplementation 500-1600 mg daily for 0.5-7 years with or without vitamin D does not reduce total fractures, hip fractures, vertebral fractures, or non-vertebral fractures in older adults without osteoporosis (95822,112486). A large-scale study in postmenopausal females aged 50-79 years who were enrolled in the Women's Health Initiative (WHI) suggests that calcium 1000 mg plus vitamin D 400 IU daily for 7 years only modestly improves bone mineral density (BMD) and does not significantly reduce fracture risk. This lack of effect may have been due to low adherence to the treatment regimen. In those who were 80% adherent, the combination of calcium plus vitamin D reduced the risk of hip fracture by about 29% (14282). Also, some clinical research shows that taking calcium carbonate 1000 mg and vitamin D 400 IU for 5 years does not attenuate loss of height after menopause when compared with placebo (95810). Additional meta-analyses of clinical and observational evidence suggest that calcium supplementation is not associated with a reduced risk of vertebral or nonvertebral fractures, such as hip fractures (38589,38888,98895). Some other research has suggested that calcium in combination with vitamin D reduces fracture risk in older patients without osteoporosis (980,1836,8818,12930,12933,12952,38849,102145,107235); however, this research is confounded by a number of variables, including the presence of hormonal therapy and differing levels of fracture risk at baseline (1836,8818,95822). Conflicting findings on this topic might also be due to genetic differences in patient populations. A population analysis of the WHI study found that, in older females with the lowest genetic susceptibility to low BMD, taking calcium with vitamin D is associated with a reduction in fracture risk. However, in females with a higher genetic susceptibility to low BMD, there is no association between supplementation and fracture risk. This might be because individuals with a lower susceptibility to low BMD are also more responsive to calcium and vitamin D supplementation (97357). As of April 2018, the U.S. Preventative Services Task Force (USPSTF) concludes that there is insufficient evidence to determine whether supplementing with vitamin D >400 IU daily along with calcium >1000 mg daily is safe and effective for preventing fractures in community dwelling adults without vitamin D deficiency, osteoporosis, or a history of fracture. USPSTF recommends against supplementing with calcium 1000 mg daily or less along with vitamin D 400 IU daily or less for preventing primary fractures in community-dwelling postmenopausal females (95695).
• Obesity. Oral calcium does not seem to improve weight loss in adults or children with overweight or obesity. Details: Observational research has found that adults and children with low calcium intake are more likely to gain weight, have a higher body mass index (BMI), and be overweight or obese when compared to people with high calcium intake (12124,12125,12126,12127,14265). Additional observational research has found that increasing calcium intake is associated with weight loss in females; the results in males have been conflicting (12127,15602,15603). Despite these findings from observational research and a few small clinical studies (12128,15397,14438,98905,113918), most clinical research has found that increased calcium intake does not increase weight loss (12052,13138,15396,15399,38985,39004,97356). A meta-analysis of 20 clinical studies shows that daily dietary and supplemental calcium intake that meets the dietary reference intake (DRI) of 1000 mg or more daily does not increase weight loss in overweight individuals or patients with obesity when compared with intake below the DRI (95813). An older meta-analysis of 13 clinical trials also shows that increased dietary and supplemental calcium intake does not increase weight loss (15605).
• Overall mortality. Oral calcium does not seem to reduce overall mortality. Details: While some population research has found that calcium taken in combination with vitamin D in older females is associated with a lower risk of death (97353), most evidence shows that calcium, with or without vitamin D, has no effect on all-cause mortality (93533,97308,113584).

INEFFECTIVE

• Cardiovascular disease (CVD). Oral calcium does not reduce the risk of developing CVD and may actually increase risk in some patients. Details: Clinical research shows that calcium does not decrease CVD risk. Several separate meta-analyses of clinical and population research involving over 50,000 patients show that taking calcium 600-1200 mg daily for up to 7 years does not reduce the risk of CVD-related outcomes, including stroke and myocardial infarction, cardiovascular death, or overall mortality (39018,91350,92994,93533,97308,98902,107231,107233). No association was found between total dietary or supplemental calcium intake with or without vitamin D and the risk of CVD or mortality (91350,93533,97308). In fact, some population and clinical research has found that when calcium is used alone or with vitamin D, there is an INCREASED risk of CVD and coronary heart disease (38077,107233). However, other clinical research disagrees (93533). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of CVD and coronary heart disease by 1.1-1.2 times when compared with control. However, the majority of the included research evaluated postmenopausal females and it is unclear if this finding is applicable to other populations (107233).
• Chemotherapy-induced peripheral neuropathy. Intravenous calcium does not prevent nerve pain in patients given oxaliplatin. Oral calcium has not been evaluated for this purpose. Details: While pooled analyses of cohort studies and randomized controlled trials suggest that calcium and magnesium infusion decreases the incidence of oxaliplatin-induced neurotoxicity, a meta-analysis of only randomized controlled trials shows that the infusion has no effect in preventing neurotoxicity (90028,90029,90031). Additionally, clinical trials show that administering calcium gluconate 1 gram with magnesium sulfate 1 gram intravenously immediately before, or before and after, the administration of a single oxaliplatin cycle (90005), or over the entire 6-cycle course of oxaliplatin, does not improve symptoms of neurotoxicity when compared with placebo (96474).
• Myocardial infarction (MI). Oral calcium does not prevent MI. When taken in the absence of vitamin D, oral calcium may increase the risk of MI. Details: Population research has found that increased dietary intake of calcium is associated with a decreased risk of MI (91350). However, a 2010 meta-analysis of clinical research shows that taking calcium at a dose of at least 500 mg daily is associated with an approximate 30% INCREASE in the risk of MI in patients over the age of 40. According to this analysis, one additional case of MI will occur for every 69 patients that take calcium for 5 years (17482). A more recent meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of MI by 1.2 times when compared with control. However, the majority of the included research studied postmenopausal females and it is unclear if this finding is applicable to other populations (107233) In contrast, other meta-analyses of clinical research have shown that taking calcium for up to 7 years is NOT associated with an increased risk of MI, including a meta-analysis that only included postmenopausal females (93533,107231). Reasons for these discrepancies are not entirely clear. It may relate to whether calcium is taken as monotherapy or in combination with vitamin D. When taken with vitamin D, which is commonly recommended, calcium supplementation does not appear to be associated with an increased risk of MI in postmenopausal females (93533). Also, the association between calcium supplementation and MI risk may be influenced by the amount of calcium consumed as part of the diet. Supplementation with calcium may be associated with an increased risk of MI in people with dietary calcium intake above 805 mg daily, but not in those with dietary calcium intake below 805 mg daily (17482)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alcohol use disorder. It is unclear if oral calcium is beneficial for alcohol use disorder. Details: Preliminary clinical research shows that taking calcium carbonate 800 mg and vitamin D 200 IU orally daily for 14 days modestly reduces alcohol craving scores and withdrawal scores when compared with placebo in adults with alcohol dependence that are undergoing withdrawal. Taking calcium carbonate did not reduce the need for diazepam; however, the study may have been inadequately powered to detect a difference between groups (107234).
• Atherosclerosis. It is unclear if oral calcium is beneficial for atherosclerosis. Details: A population study has found that taking calcium 1.2 grams daily for 3 years has no effect on carotid intima thickness or carotid atherosclerosis incidence. A total calcium intake (dietary and supplemental) of at least 1794 mg daily in older females may be associated with a decreased risk of carotid atherosclerosis when compared with a total calcium intake below 1010 mg daily (97351).
• Autism spectrum disorder. It is unclear if oral calcium during pregnancy is beneficial for reducing the odds of autism spectrum disorder in the offspring. Details: A small observational study found that calcium supplementation during pregnancy is associated with a 52% reduced odds of an autism spectrum disorder in the offspring (98900).
• Brain tumor. It is unclear if dietary calcium intake is associated with risk of brain tumor. Details: A meta-analysis of 4 case-control studies has found that higher dietary calcium intake is associated with a lower odds of brain tumor when compared with lower dietary intake (113922). The validity of this finding is limited by the exploratory nature of the included studies, which analyzed all dietary ingredients for any potential associations.
• Cancer. Oral calcium alone does not seem to prevent cancer. It is unclear if oral calcium with vitamin D is beneficial for preventing cancer. Details: Taking calcium alone does not seem to significantly reduce the risk of cancer (12118,15629). The role of calcium in cancer prevention when taken along with vitamin D is controversial, as conflicting results exist. One clinical trial shows that healthy postmenopausal females who take supplemental calcium 1400-1500 mg daily plus vitamin D3 (cholecalciferol) 1100 IU daily have a 60% lower relative risk for developing cancer of any type. Approximately 25 postmenopausal females would need to take this combination for 4 years to prevent one occurrence of cancer (15629). However, a more recent clinical study shows that healthy postmenopausal females who take supplemental calcium 1500 mg daily plus vitamin D3 (cholecalciferol) 2000 IU daily do not have a reduced risk of cancer at 4 years (93943). Reasons for the disparate results are not entirely clear. The discrepancies do not appear to be related to baseline vitamin D levels or different study populations. It is possible that, given the 10-year time lapse between the two publications, the discrepancies result from differences in cancer detection capability. Also, since cancer risk was a secondary outcome measure in the earlier study and a primary outcome measure in the more recent study, it is possible that the discrepancies result from differences in statistical methodologies. The effect of vitamin D and calcium on cancer risk in males and younger patients is not known. There is also interest in using calcium for reducing the risk of hematological malignancies. An analysis of the Women's Health Initiative study shows that taking calcium 1000 mg daily in combination with vitamin D3 400 IU for up to 10 years is associated with a 20% reduction in the risk of hematologic malignancies when compared with placebo. However, no effect on hematologic malignancy related mortality was seen (97354).
• Depression. It is unclear if oral calcium is beneficial for depression prevention. Details: Population research has found no association between a higher dietary intake of calcium and the risk of depression when compared with a lower dietary intake of calcium (96480).
• Diabetes. It is unclear if dietary calcium intake is associated with type 2 diabetes risk. Details: Some population research has found that a higher intake of calcium from the diet or supplements, alone or in combination with vitamin D, is associated with a lower risk of developing type 2 diabetes when compared with lower calcium intake (14265,16713,96473,113929). One meta-analysis of cohort and cross-sectional studies found that the highest level of dietary calcium intake is associated with an 18% relative reduction in risk of type 2 diabetes when compared with the lowest level of intake. A dose-response analysis suggests that each 300, 600, and 1000 mg per day increase in dietary calcium intake is associated with a 7%, 14%, and 23% reduced risk of type 2 diabetes, respectively (113929). However, population research is often limited by confounding variables. For example, one analysis suggests that any beneficial effect might be influenced by concomitant magnesium intake (96473,113929), while another suggests that any benefit from increased intake may be more pronounced in females, adults aged 50 years or older, and Asian populations (113929). Furthermore, other population research has found that serum calcium levels higher than 9.6 mg/dL are associated with greater risk of developing diabetes in Chinese adults with osteoporosis (95815).
• Dyslipidemia. It is unclear if oral calcium is beneficial for dyslipidemia. Details: One clinical study in adults with mild to moderate hypercholesterolemia shows that adding calcium carbonate 400 mg three times daily to a low-fat diet (American Heart Association Step 1) for 6 weeks reduces low-density lipoprotein (LDL) cholesterol levels by 4% and increases high-density lipoprotein (HDL) cholesterol levels by 4% when compared with the low-fat diet and placebo (2557). In contrast, a clinical study in females with dyslipidemia shows that taking calcium 800 mg daily for 2 years INCREASES total cholesterol levels and carotid intima-media thickness in postmenopausal, but not premenopausal, females when compared with placebo (97350). Calcium supplementation has also been evaluated in combination with vitamin D. A meta-analysis of randomized controlled trials including adults with normolipidemia and dyslipidemia shows that taking calcium 500-2000 mg daily and vitamin D 200-7142 IU daily modestly improves HDL cholesterol and triglyceride levels, but not LDL cholesterol levels, when compared with placebo. Subgroup analyses suggest that calcium and vitamin D supplementation is most beneficial in patients with dyslipidemia at baseline (107227). The relationship between dietary calcium intake and serum lipid levels has also been evaluated in observational research. A meta-analysis of 7-11 observational studies found that dietary calcium intake is not associated with total cholesterol levels, although small differences in individual lipid parameters were identified. Additionally, a meta-analysis of 4-9 observational studies suggests that calcium intake is not associated with the risk of developing hypertriglyceridemia, hypercholesterolemia, or low HDL. A subgroup analysis found that higher calcium intake may be associated with lower triglyceride levels in Asian populations (113927). Overall, these findings are limited by significant heterogeneity and the cross-sectional nature of the included studies.
• Dysmenorrhea. It is unclear if oral calcium is beneficial for reducing pain associated with dysmenorrhea. Details: Clinical research shows that taking calcium carbonate 1000 mg with vitamin D 5000 IU daily for three menstrual cycles does not reduce pain when compared with placebo in patients with primary dysmenorrhea (95821). However, calcium carbonate 1000 mg taken alone seems to reduce pain when compared with placebo.
• Endometrial cancer. It is unclear if oral calcium is beneficial for endometrial cancer prevention. Details: A meta-analysis of population research suggests that calcium supplements may reduce the risk of endometrial cancer, but dietary calcium does not seem to have any effect (38893).
• Exercise-induced muscle damage. It is unclear if oral calcium is beneficial for reducing exercise-induced muscle damage. Details: A very small clinical study in resistance-trained adults shows that taking calcium carbonate 500 mg 4 times daily for 3 weeks does not attenuate exercise-induced muscle damage from bench presses when compared with placebo (113933). This study may have been inadequately powered to detect a difference between groups.
• Fall prevention. It is unclear if oral calcium with vitamin D is beneficial for preventing falls. Details: Research suggests that calcium in combination with vitamin D, but not calcium alone, might prevent falls by decreasing body sway and normalizing systolic blood pressure (6362,11939,39038). Some experts think the combination of calcium and vitamin D may be important (11916). Preliminary clinical research in adults residing in a health care facility shows that taking vitamin D supplements while increasing dietary calcium and protein for 2 years reduces falls by 11% when compared with standard diets. Intervention diets were supplemented with milk, yogurt, and cheese to provide calcium 1142 mg and protein 69 grams daily (107235). There might also be different effects in females compared to males. In one study, females aged 65 years or older who took vitamin D 700 IU plus calcium citrate 500 mg daily over a 3-year period had a 46% lower risk of falling. However, this combination did not decrease falls in males (14291).
• Fluorosis. Oral calcium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking calcium orally, in combination with ascorbic acid (vitamin C) and vitamin D, seems to be effective for reducing excessive fluoride levels in children and improving symptoms of fluorosis in children aged 6-12 years (990).
• Heart failure. It is unclear if oral calcium in combination with vitamin D is beneficial for preventing heart failure. Details: Based on a secondary analysis of a large-scale clinical trial (Women's Health Initiative), taking calcium 1000 mg with vitamin D 400 IU daily does not reduce the risk of heart failure in the overall population or in individuals at high risk. However, in a subgroup of postmenopausal females without risk factors for heart failure, calcium and vitamin D supplementation might reduce the risk of developing heart failure by about 37% (97307).
• Lead toxicity. It is unclear if oral calcium is beneficial for reducing blood levels of lead. Details: Lead is mobilized along with calcium from bone during pregnancy and lactation, resulting in increased serum concentrations of lead. One clinical study suggests that calcium supplementation does not significantly decrease these elevated lead concentrations (1586). However, another clinical study suggests that taking calcium reduces blood lead levels by 11% when compared with placebo, with greatest effects observed in those with high baseline levels of lead (38957).
• Lyme disease. Although there is interest in using oral calcium for Lyme disease, there is insufficient reliable information about the clinical effects of calcium for this condition.
• Metabolic syndrome. It is unclear if oral calcium alone or with vitamin D is beneficial for metabolic syndrome prevention. Details: Population research has found that a higher intake of calcium from diet and supplements alone, or in combination with vitamin D, is associated with a lower risk of developing metabolic syndrome when compared with lower calcium intake (14265,16713).
• Nephrotic syndrome. It is unclear if oral calcium with vitamin D is beneficial for preventing nephrotic syndrome. Details: Clinical research shows that taking calcium 500-1000 mg daily for 3 months in combination with vitamin D3 60,000 IU daily or weekly for 4 weeks has no effect on bone mineral density or the risk of relapse in children with steroid-sensitive nephrotic syndrome (97355).
• Nonmelanoma skin cancer. It is unclear if oral calcium is beneficial for preventing keratinocyte carcinomas. Details: In middle aged and older adults recently diagnosed with a colorectal adenoma, clinical research shows that taking calcium 1200 mg daily as calcium carbonate for 3-5 years does not reduce the incidence of keratinocyte cancer when compared with placebo over a median of 8 years. A sub-group analysis shows that taking calcium alone or with vitamin D3 1000 IU daily reduced the risk of invasive cutaneous squamous cell carcinoma by a moderate amount, but had no effect on the risk of basal cell carcinoma (104622).
• Oral mucositis. When used in combination with fluoride treatments, a calcium phosphate mouth rinse seems to prevent and reduce mucositis-related pain in patients undergoing hematopoietic stem cell transplantation (HSCT). Details: A small clinical study in patients undergoing HSCT shows that using a particular mouth rinse (Caphosol, EUSA Pharma) containing calcium phosphate, in combination with fluoride treatments, reduces days of mucositis, the duration of pain, and the dose and days of morphine used when compared with placebo and fluoride treatment (38611).
• Ovarian cancer. It is unclear if oral calcium is beneficial for ovarian cancer prevention. Details: An older meta-analysis of 12 cohort studies found that dietary calcium intake is not associated with a reduced risk of ovarian cancer (38792). However, a more recent pooled analysis of 15 cohort and case-control studies has found that the highest intake of dietary or dairy calcium is associated with a 20% lower risk of ovarian cancer when compared to the lowest intake (97349).
• Postpartum depression. It is unclear if oral calcium is beneficial for reducing postpartum depression risk. Details: Preliminary clinical research shows that taking calcium 2 grams daily beginning at 11-21 weeks gestation reduces depression at 12 weeks postpartum when compared with placebo. However, no benefit is seen at 6 weeks postpartum (39447).
• Pregnancy-related leg cramps. It is unclear if oral calcium is beneficial for preventing leg cramps during pregnancy. Details: A small clinical study shows that taking calcium 1 gram twice daily (as a mixture of salts) for 2 weeks can reduce pregnancy-related leg cramps during the second half of pregnancy when compared with no treatment (2567).
• Prematurity. It is unclear if supplemental calcium is beneficial for the growth and development of preterm infants. Details: A small clinical study in preterm infants consuming human milk shows that supplementation with calcium 45 mg/kg daily and phosphorus 25 mg/kg daily does not affect infant weight, length, head circumference, or risk of osteopenia after 6 weeks when compared with human milk alone (113924). However, the duration and size of this study may have been too limited to detect any difference between groups.
• Preterm labor. It is unclear if oral calcium reduces the risk of preterm labor. Details: A meta-analysis of 10 clinical studies shows that taking calcium supplements during pregnancy does not reduce the risk of preterm labor when compared with placebo (113909). A separate meta-analysis of 7 clinical studies conducted in China, which evaluated the benefits of calcium carbonate 500-600 mg daily taken in conjunction with aspirin 50-75 mg daily during pregnancy, shows that this combination reduces the relative risk of preterm labor by 74% when compared with routine care (113913).
• Prostate cancer. It is unclear if oral calcium is beneficial for prostate cancer prevention. Details: Some clinical research shows that taking calcium 1200 mg daily might decrease the risk of developing prostate cancer (14133). However, some epidemiological research suggests that consuming very high doses of calcium, over 2000 mg daily, might actually increase the risk of developing prostate cancer (14134). Some epidemiological research also suggests that doses greater than 1500 mg daily increase the risk of poorly differentiated, clinically advanced, and fatal prostate cancer (14132). Consumption of dairy products has also been weakly linked to a modest increase in risk of prostate cancer (98894). However, contradictory research suggests that there is no association between dietary intake of calcium and overall risk of prostate cancer (14131,14132,104630).
• Stroke. It is unclear if oral calcium is beneficial for stroke prevention. Details: Some population research has found that increasing dietary calcium intake is associated with a decreased risk of ischemic stroke (4822,38678). However, other population research has found that increasing dietary calcium intake is not associated with a decreased risk of stroke (91350). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years does not affect the risk of stroke when compared with control. However, the majority of the included research evaluated postmenopausal females, and it is unclear if this finding is applicable to other populations (107233).
• Vertigo. Oral calcium with vitamin D might reduce positional vertigo; the effect of calcium when used alone is unclear. Details: A large clinical study in adults with recurrent benign paroxysmal positional vertigo shows that taking calcium 500 mg and vitamin D 400 IU twice daily for one year reduces annual recurrence of vertigo by 27% when compared with no treatment. The number needed to treat to prevent vertigo was 3.7 (103681). It is unclear if this benefit is due to vitamin D, calcium, or the combination. More evidence is needed to rate calcium for these uses.

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POSSIBLY EFFECTIVE

• Athletic performance. Oral creatine monohydrate seems to modestly improve rowing, jumping, and soccer performance. It is unclear if it is beneficial for sprinting, cycling, swimming, or tennis performance. Details: In competitive rowers, most clinical research shows that taking creatine 20 grams or 240-250 mg/kg daily for 5 days significantly improves aerobic and anaerobic performance (4605,4607,46569,46605,46833). Specifically, creatine decreases 1000-meter rowing time by 2.4 seconds and 2500-meter rowing time by 6.5 seconds and increases time to fatigue by 9.7 seconds when compared with placebo (4607,46605,46833). To improve rowing performance, creatine 20 grams (or 240-250 mg/kg) daily for 5 days has been used (4605,4607,46605,46833). Additionally, most clinical research shows that taking creatine 20-30 grams daily for 5-7 days improves jumping height by up to 6 cm when compared with placebo in active males (11331,13661,46626,46704), although some conflicting results exist (6924,46601). When compared with placebo, creatine also appears to improve spike jumping and block jumping in male volleyball players (46762), as well as peak and mean power of stationary roundhouse kicks in male trained taekwondo athletes (108333). In young male soccer players, preliminary clinical research shows that taking creatine 10 grams three times daily for 7 days can increase performance on a specific dribbling speed test by up to 2.8 seconds when compared with placebo (46626). In young female soccer players, preliminary clinical research shows that taking creatine 5 grams four times daily for 7 days followed by 5 grams daily for 5 weeks in conjunction with plyometric training modestly increases body mass index, jump and power performance, and repeated sprinting performance when compared with either plyometric training with placebo or standard soccer drills (95961). Research evaluating creatine supplementation for sprinting, cycling, high-intensity-interval training (HIIT), and swimming has been inconsistent. The reason for these mixed findings is unclear. A meta-analysis of small clinical trials shows that taking creatine decreases the peak oxygen uptake (VO2 max) during running and cycling, suggesting a worsening of aerobic fitness (108330). However, another meta-analysis of randomized controlled trials shows that taking creatine up to 20 grams orally daily for 3-7 days modestly improves mean power, but not peak power or fatigue, during repeated running or cycling sprint intervals when compared with placebo (112206). In addition, a meta-analysis of randomized clinical trials in trained athletes shows that taking creatine up to 20 grams orally daily for 5-42 days does not improve endurance running or cycling performance when compared with control (112214). A potential explanation for these conflicting results is that the studies failing to show an improvement are likely underpowered, with sample sizes of only 6-32 subjects (4582,4601). For instance, some small clinical trials show that taking creatine 20-30 grams daily for 5-7 days can improve sprint times by up to 3% and decrease time to exhaustion by up to 13% when compared with placebo in trained athletes (6924,11331,46558,46567,46626,46819); however, others show that taking creatine 20-25 grams daily for 3-7 days does not improve sprint velocity, 60-meter or 150-meter sprint times, or fatigue in these individuals (46603,46656,46797,46806,112216). In trained athletes, untrained yet healthy adults, and sedentary adults, some clinical research shows that taking creatine 10-35 grams daily for 4-7 days significantly improves power output, peak power, and fatigue indices while cycling (4591,4592,4593,4594,4602,4604,6926,10064,46522,46528) (46547,46568,46601,46614,46820); however, significant improvements in cycling performance with creatine are lacking in other studies (4582,4595,4596,4597,4598,4599,4600,4606,46520,46538) (46646). Similarly, in trained swimmers, some clinical research shows that creatine improves swimming performance (4601,4603,46600,46655,46725,46805), with a few studies reporting improvements of 1.3-2 seconds in 100-meter swim times when compared with placebo (46600,46725,46805). However, creatine does not improve 25-, 50-, or 100-meter swim performance in other trials (2106,4601,46798). To improve swimming performance, creatine 9-25 grams daily for 4-9 days has been used (4601,4603,46600,46655,46725,46805), with lower maintenance doses of 2.25-10 grams daily for 8-9 days used in some cases (4601,46600). Preliminary clinical research in trained tennis players shows that taking creatine 5 grams four times daily for 5 days or 0.3 grams/kg daily for 6 days followed by 0.03 grams/kg daily for 4 weeks does not appear to improve stroke power, stroke precision, serving speed, sprinting, or shuttle run time when compared with placebo (46536,46673). Taking creatine (Creapure, AlzChem AG) 0.3 grams/kg daily for 5 days, followed by 0.1 grams/kg daily for 23 days, while undergoing HITT 3 days each week does not improve physical performance outcomes when compared with placebo in healthy young females (95965). A preliminary clinical trial in elite female handball players shows that the beneficial effects of creatine monohydrate 0.3 grams/kg for 5 days followed by 0.03 grams/kg are not dependent on the time of day of supplementation (108332). Although this suggests that the circadian rhythm does not influence the ergogenic effect of creatine, this study was small and may have been underpowered to detect any differences. One clinical study in actively training firefighters shows that adding creatine 5 grams to daily supplemental protein and carbohydrates for 3 weeks reduces rescue and forcible entry times, but does not improve hose line advance, stair climb, or aerobic speed times, when compared with protein and carbohydrate supplementation alone (113673). One clinical study compared the efficacy of creatine monohydrate with that of creatine nitrate. At equivalent doses of 12 grams daily for 7 days, followed by 3 grams daily for 21 days, creatine nitrate and creatine monohydrate produce similar increases in fat-free mass, lean mass, and intramuscular creatine concentrations, and similar improvements in bench press lifting volume and average power output. The lower dose of creatine nitrate 6 grams daily for 7 days followed by 1.5 grams daily for 21 days does not demonstrate performance improvement benefits or result in increased intramuscular creatine (95959). In 2018, the International Society of Sports Nutrition (ISSN) recommended creatine monohydrate, but not creatine nitrate, as an ergogenic nutritional supplement for increasing athletic capacity and lean body mass (101009). Creatine has also been evaluated in combination with caffeine. A very small clinical study in healthy adult males shows that taking creatine 20 grams daily for a 5-day loading period and then adding caffeine 5 mg/kg daily for the next 3 days improves anaerobic power, but not anaerobic capacity, when compared with placebo (115980). Further research is needed to determine whether creatine is beneficial when taken with other erogenic ingredients.
• Cerebral creatine deficiency syndromes. Oral creatine seems to improve some symptoms of the cerebral creatine deficiency syndromes guanidinoacetate methyltransferase (GAMT) deficiency and arginine-glycine amidinotransferase (AGAT) deficiency. It is unclear if oral creatine is beneficial for creatine transporter defect. Details: Three inborn errors of metabolism, GAMT deficiency, AGAT deficiency, and creatine transporter defect, cause low cerebral creatine levels, resulting in mental retardation, seizures, autism, and movement disorders. In children with GAMT deficiency, taking creatine orally, 400-500 mg/kg daily for up to 8 years or 4-8 grams daily for up to 25 months, increases brain creatine levels and improves movement disorders and seizure frequency, but has little effect on intellectual ability (46722,46796,46804). Children with AGAT deficiency who take creatine 400-800 mg/kg daily for up to 8 years seem to have improved attention, language development, and academic performance (46584,46769). However, research in children up to 10 years of age with creatine transporter defect shows that taking a mixture of creatine, L-arginine, and glycine orally for 4-6 years does not increase brain creatine levels or improve motor or cognitive functioning (46757).
• Muscle strength. Oral creatine seems to modestly improve muscle strength. It is unclear if topical creatine is beneficial. Details: Pooled analyses of clinical trials assessing upper limb strength, lower limb strength, and body composition have evaluated creatine provided in typical loading doses of 20 grams daily or 0.3 grams/kg daily, although doses up to 26 grams daily have been used, in single or divided doses for 5-7 days (90323,90330,93626,93627,108316,108336,112213). Creatine maintenance doses ranged from 1.25-27 grams daily for up to 32 weeks (90323,90330,93626,93627,108316,108336,115978). In some studies, creatine doses of usually 0.1 grams/kg have been taken daily for up to 12 months in the absence of a loading dose. In others, creatine was taken only on training days (108316). Meta-analyses of research in the general adult population show that taking creatine with or without resistance training seems to improve handgrip strength, upper limb strength, and lower limb strength, with a small-to-moderate overall effect (93626,93627). In combination with resistance training, creatine also appears to be beneficial for upper and/or lower limb strength in older adults and those at risk for functional disability, although benefits on both domains have not been demonstrated in all analyses (90323,90330,108316,108336,115978). A meta-analysis limited to studies involving older females shows that while taking creatine with resistance training increases upper body strength when compared with placebo, improvements to lower body strength are limited to those studies providing supplementation for at least 24 weeks (108336). Meta-analyses of studies involving middle-aged adults, older adults, and those with chronic conditions at risk for functional disability show that creatine supplementation combined with resistance training appears to increase total body mass by 1 kg and lean body mass by 0.9-1.3 kg when compared with placebo (90323,90330,108316,115978). However, other meta-analyses of studies in older adults show no effect of creatine combined with resistance exercise on muscle mass or absolute fat mass, while effects on body fat percentage are inconsistent (90323,108335,108336,113671). While the analyses above provide a good estimate of creatine's effect on muscle strength, it is important to note that a large number of clinical trials assessing strength in patients taking creatine have been published. These studies included varying methodologies, small sample sizes, and a wide range of creatine doses, dosing times, and study durations. These differences may explain why some studies have found a benefit with creatine supplementation (2100,2101,4580,6015,6924,6928,10062,13661,46507,46510)(46523,46528,46550,46551,46561,46562,46567,46570,46581,46589)(46601,46613,46615,46618,46626,46628,46667,46709,46720,46725)(46761,46762,46801,46815,90321,90327,95958,95960,102162,103279)(104668,104670,108329,112213,112793), while others have not (4569,4570,4571,4572,4588,6183,46520,46539,46554,46569)(46579,46594,46656,46665,46673,95963,95967,95968,95969,102168,104669)(104671,108334). Topical creatine has also been evaluated. Applying 3.5 mL of a specific cream (Delivra, LivCorp Inc.) containing creatine 1% daily for 7 days moderately improves peak and average muscle power in healthy males when compared with a placebo cream. However, some study participants were also taking oral creatine monohydrate 7 grams three times daily and others were taking an oral placebo. An acute application of the cream at doses of 3.5 mL or 7 mL 30 minutes before exercise does not improve power (104669).
• Sarcopenia. When used for up to 12 weeks in combination with resistance training, oral creatine seems to modestly improve muscle strength in older adults. It is unclear if oral creatine is beneficial when used as a single dose or for more than 12 weeks. Details: Most research shows that taking creatine while taking part in a resistance training program can increase upper and/or lower body muscle strength in older adults (90323,90330,95958,102162,108316,108336). One meta-analysis of research in adults 50 years of age and older taking part in resistance training programs shows that creatine supplementation improves chest press strength with a moderate effect size, but does not improve leg press strength, when compared with placebo (90330). Also, another meta-analysis focusing on adults 45 years of age and older taking part in resistance training shows that creatine supplementation improves chest press strength by 1.74 kg and leg press strength by 3.25 kg when compared with placebo, with no effect on knee extension or biceps curl measurements (90323). A meta-analysis limited to studies involving older females shows that while taking creatine with resistance training increases upper body strength when compared with placebo, improvements to lower body strength are limited to those studies providing supplementation for at least 24 weeks (108336). However, some negative findings exist. Some clinical research in postmenopausal females with osteopenia shows that taking creatine monohydrate 1-3 grams (Creapure, AlzChem AG) daily for 1-2 years without participation in resistance training does not alter muscle function when compared with placebo (95969,102168). In addition, in healthy males aged 49-69 years, a small clinical trial shows that taking creatine monohydrate (Rivalus Inc.) 0.05 grams/kg twice daily, while undergoing supervised resistance training three days each week for one year, does not alter muscle strength when compared with placebo (104671). One clinical study shows that a single loading dose of creatine monohydrate 20 grams (Creapure, AlzCHem AG) taken 3 hours prior to exercise does not improve leg press or chest press muscle endurance in aging males (95968). Also, lower doses of creatine added to whey protein supplementation do not seem to be beneficial. One small study in adults 65 years or older shows that adding creatine monohydrate 2.5 grams twice daily along with whey protein 10 grams twice daily and resistance training for 14 weeks does not improve muscle function when compared with whey protein and resistance training alone (95966). Most research also suggests that creatine improves total muscle mass in older adults, although conflicting research exists. Some studies show that taking creatine while taking part in a resistance training program seems to increase muscle mass in older adults (90323,90330,108316,108329). Meta-analyses of studies involving middle-aged and older adults show that creatine supplementation combined with resistance training appears to increase total body mass by 1 kg and lean body mass by 0.9-1.3 kg when compared with placebo (90323,90330,108316). However, a meta-analysis of studies limited to older females shows that there was no effect of creatine on muscle mass (108336). Also, in healthy males aged 49-69 years, a small clinical trial shows that taking creatine monohydrate (Rivalus Inc.) 0.05 grams/kg twice daily, while undergoing supervised resistance training three days each week for one year, does not alter body composition when compared with placebo (104671). Despite these generally beneficial findings, significant decreases in fat mass following creatine supplementation in older adults are lacking, and effects on body fat percentage are inconsistent (90323,95958,108335).

POSSIBLY INEFFECTIVE

• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). Oral creatine does not seem to reduce ALS symptoms or increase survival. Details: Taking creatine orally, 5-10 grams daily for 9-16 months, or 20 grams daily for 5-7 days followed by 3-5 grams daily for 6 months, has no effect on disease progression, respiratory function decline, or survival in patients with ALS (11332,16389,46553,46574,46707). In one case series, some patients experienced temporary improvement in muscle strength while taking 20 grams daily during the first week, but this was not maintained (46553).
• Huntington disease. Oral creatine does not seem to reduce symptoms of this condition. Details: Taking creatine orally has no effect on motor function or symptom scores in people with Huntington disease (46598,46609,95957). Clinical research shows that taking creatine 5-40 grams daily (average dose of 31.6 grams) for 24 months does not improve total motor score or total functional capacity in patients with early manifest Huntington disease (95957).
• Osteopenia. Oral creatine does not seem to be beneficial for osteopenia. Details: In postmenopausal adults with osteopenia, taking creatine monohydrate (Creapure, AlzChem GmbH ) 1-3 grams daily for 1-2 years does not improve bone mineral density (BMD) when compared with placebo (95969,102168). Another clinical trial in postmenopausal adults with osteopenia or osteoporosis shows that taking creatine monohydrate (Probiotica) 20 grams daily for 5 days and then 5 grams daily for the next 23 weeks, with or without exercise training, does not improve bone mass when compared with placebo (90321). Also, a small clinical trial in older adults, most of which had osteopenia, shows that taking creatine monohydrate (Rivalus Inc.) 0.05 grams/kg twice daily in combination with resistance training for 12 months modestly improves some measures of bone area, but not BMD, when compared with placebo (108329). Other research has evaluated creatine in patients without a definite diagnosis of osteopenia. One study shows that taking creatine (Rivalus Inc.) 0.1 gram/kg daily for 12 months or creatine (Creapure AlzChem Trostberg GmbH) 0.1 grams/kg three times weekly does not affect BMD in adults age 50 and up taking part in resistance training (104671,104674). In contrast, a small clinical trial in postmenopausal patients shows that taking creatine monohydrate (Rivalus Inc.) 0.1 gram/kg daily for 12 months while undergoing a resistance training program has a small preventive effect on bone loss at the femoral neck, but not the hip or spine (104673). However, other preliminary clinical research in postmenopausal patients shows that taking creatine (Creapure, AlzChem AG) 0.14 grams/kg orally daily for 2 years does not improve BMD when compared with placebo (112219). Also, preliminary clinical research shows that taking creatine 0.3 grams/kg for 5 days and 0.07 grams/kg for the remainder of a 12-week resistance training session increases BMD in elderly males over 70 years (46664). More information is needed to determine if creatine is beneficial when used in combination with a resistance training program in older adults.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral creatine is beneficial for the treatment or prevention of age-related cognitive decline. Details: Population research in the US has found a positive association between dietary creatine intake and a specific measure of cognitive function, the WAIS III Digit Symbol Substitution Test (DSS). In addition, this measure of cognitive function was highest in individuals who consumed more than 0.95 grams daily (108331). However, clinical research is conflicting. A small clinical trial in older adults shows that taking creatine monohydrate (Creapure, Deguss AG) 5 grams four times daily for one week has modest beneficial effects on some measures of cognitive function, but not others, when compared with baseline or placebo (46686). Another small clinical trial shows that taking creatine monohydrate 5 grams four times daily for five days, and then 5 grams daily for a total of 4 weeks, does not improve cognitive function when compared with placebo (108339).
• Aging skin. Topical creatine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that applying a cream containing creatine 0.2%, guarana 0.4%, and glycerol 8% to the face daily for 6 weeks reduces wrinkles and skin sagging when compared to baseline (46766). Other research shows that a specific cream containing creatine 0.2% and folic acid 0.03% (Nivea Visage DNAage, Beiersdorf AG) reduces wrinkles and roughness and improves firmness of photo-aged skin when compared to baseline (46696). The effect of topical creatine alone on aging skin is unclear. Also, the validity of these findings is limited by the lack of a comparator group.
• Arsenic poisoning. It is unclear if oral creatine is beneficial in patients with arsenic poisoning. Details: Preliminary clinical research in adults regularly consuming well water that contains arsenic shows that taking creatine 3 grams orally daily for 12 weeks lowers the concentration of certain serum arsenic metabolites when compared with control (112212). Creatine has not been studied for management of acute arsenic poisoning.
• Chronic fatigue syndrome (CFS). It is unclear if oral creatine is beneficial for improving post-viral CFS. Details: A very small clinical study in adults who developed CFS after COVID-19 shows that taking creatine 4 grams with breakfast daily for 6 months improves body aches and the ability to concentrate, but does not affect fatigue levels or time to exhaustion, when compared with an inulin placebo (113487). Although many other CFS-related symptoms were evaluated in this study, no statistical methods were implemented to control for multiplicity, limiting the interpretation of any additional findings.
• Chronic kidney disease (CKD). It is unclear if oral creatine is beneficial in adults with CKD. Details: A small clinical study in adults with CKD undergoing hemodialysis shows that taking creatine monohydrate 20 grams daily for a week alternating with 5 grams daily for a week, for a total of 4 weeks, attenuates loss of lean body mass and reduces the malnutrition-inflammation score when compared with taking a maltodextrin control (102166). However, another very small clinical study evaluating the same regimen over a period of 12 months shows no improvement in malnutrition-inflammation score, body composition, strength, or endurance when compared with a maltodextrin control (115981).
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral creatine is beneficial in patients with COPD. Details: One clinical study shows that taking creatine 22 grams daily for 5 days, then 3.76 grams daily for 6 weeks, does not improve pulmonary function or walking distance when compared with placebo (46699). Another study shows taking creatine 5.7 grams three times daily for 2 weeks, then once daily thereafter, improves patient self-assessment of lung function, but not exercise capacity, when compared with placebo (46658). A third study shows taking creatine 0.3 grams/kg for 7 days, then 0.07 grams/kg for 7 weeks, improves walking time, but not measures of lung function, when compared with placebo (46691). A meta-analysis of the results from these and other clinical trials shows that creatine does not improve exercise capacity, muscle strength, or quality of life in COPD patients. However, the studies analyzed were of varying quality, which may limit the validity of these findings (46740).
• Cognitive function. It is unclear if oral creatine is beneficial for improving cognitive function. Details: Some preliminary clinical research in healthy adults shows that taking creatine possibly improves some measures of cognitive performance, specifically short-term memory and reasoning. However, findings related to most measures of cognitive function are inconsistent (108340). Other clinical research in healthy adults shows that taking a specific creatine product (Creapure, AlzChem) 5-20 grams orally daily for 6 weeks does not improve cognitive function, abstract reasoning, or working memory when compared with placebo (112215,113486).
• Congestive heart failure (CHF). It is unclear if oral creatine is beneficial in patients with CHF. Details: Two very small clinical studies show that taking creatine orally 20 grams daily for 5-10 days improves skeletal muscle strength and endurance, but not ejection fraction or symptoms of CHF, when compared with placebo (4562,4563). Also a small clinical study in males with class II-IV heart failure shows that taking creatine 5 grams daily for 6 months does not improve exercise capacity or ejection fraction when compared with placebo (90328). However, it is possible that these small studies were inadequately powered to detect a difference in these clinical outcomes.
• Depression. It is unclear if oral creatine is beneficial for improving symptoms of depression. Details: Preliminary clinical research shows that taking creatine 5 grams daily for 8 weeks improves response to escitalopram in females with major depressive disorder. Hamilton Depression Rating Scale (HAM-D) scores decreased by 80% when compared to baseline in those receiving creatine plus escitalopram, compared to a decrease of only 63% in those taking placebo plus escitalopram (46777). However, the World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce recommend against use of creatine for depression until more conclusive data are generated (110318).
• Diabetes. It is unclear if oral creatine is beneficial for glycemic control. Details: A meta-analysis of preliminary clinical research shows that taking creatine does not affect levels of fasting blood glucose or measures of insulin resistance when compared with placebo (108338). However, most of the studies included in this analysis were not conducted in individuals with diabetes. In people with newly-diagnosed type 2 diabetes, preliminary clinical studies show a reduction in postprandial glucose levels after taking creatine 3-6 grams orally daily for 5 days (46732,46760). The studies show that creatine 3 grams once daily has similar effects to glyburide 3.5 mg daily, and that creatine 3 grams twice daily is similar to metformin 500 mg twice daily. The effects of treatment for longer than 5 days in patients with diabetes are unknown. However, in sedentary males without diabetes, taking creatine 10 grams daily for 3 months seems to improve glucose tolerance (46682).
• Fatigue. It is unclear if oral creatine is beneficial for cognitive fatigue prevention. Details: A small clinical study in healthy young adults with mental fatigue shows that taking creatine monohydrate (Sportimaxx) 20 grams daily for 7 days improves accuracy on prolonged cognitive tasks, but not cognitive measures that require a quick response, when compared with placebo (102170).
• Fibromyalgia. It is unclear if oral creatine is beneficial for improving exercise performance in patients with fibromyalgia. Details: Preliminary clinical research shows that taking creatine 5 grams orally four times daily for 5 days, followed by 5 grams daily for a total of 16 weeks, improves leg press strength by 10% and chest press strength by 8% when compared with placebo in patients with fibromyalgia. However, creatine supplementation does not appear to improve aerobic capacity, pain, sleep, quality of life, or cognitive function (90331).
• Gyrate atrophy. Anecdotal reports suggest that oral creatine may be beneficial in some patients with gyrate atrophy. Details: Gyrate atrophy of the choroid and retina is associated with elevated plasma ornithine levels, which inhibit creatine synthesis and result in muscle fiber atrophy and eye fundus damage. Left untreated, patients with this condition progressively lose their vision (4577,4578). A small case series suggests that taking creatine 1.5 grams daily for one year might slow eye damage and visual deterioration in some patients with this condition when compared to baseline (4578). The validity of this finding is limited by the small sample size and lack of a comparator group.
• Hereditary motor and sensory neuropathy. It is unclear if oral creatine is beneficial in patients with hereditary motor sensory neuropathies. Details: Preliminary clinical studies in people with hereditary motor sensory neuropathies, such as Charcot-Marie-Tooth Disease, suggest that taking creatine orally 5 grams daily for 1-12 weeks has no effect on muscle strength, endurance, or functional capacity when compared with placebo (46548,46630,46675,46695).
• HIV/AIDS-related wasting. It is unclear if oral creatine is beneficial in patients with muscle wasting associated with HIV. Details: A small clinical study shows that taking creatine orally 20 grams daily for 5 days, then 4.8 grams daily for 14 weeks, does not increase muscle mass or strength in patients with HIV with muscle wasting when compared with placebo (46718).
• Hyperhomocysteinemia. It is unclear if oral creatine is beneficial in patients with hyperhomocysteinemia. Details: Preliminary clinical research in strict vegan adults with hyperhomocysteinemia shows that taking micronized creatine monohydrate (Bioderm) 5 grams daily for 3 weeks reduces blood levels of homocysteine by 39% when compared with baseline (102169). The validity of this finding is limited by the lack of a comparator group.
• Inflammatory myopathies. It is unclear if oral creatine is beneficial in patients with idiopathic inflammatory myopathies. Details: Preliminary clinical research in people with dermatomyositis or polymyositis shows that taking creatine orally 20 grams daily for 8 days, followed by 3 grams daily for a total of 6 months, in addition to an exercise program, decreases aggregate functional performance time by around 7% and increases shoulder abduction and hip flexion strength when compared with placebo. However, no improvements in functional index or strength as measured by elbow flexion, knee extension, or dorsi flexion are reported (15520). Taking creatine does not seem to improve muscle strength or disease activity in patients aged 7-18 years with juvenile dermatomyositis. Preliminary clinical research shows that taking creatine (AlzChem) for 4 weeks to 6 months does not improve muscle strength or disease activity when compared with placebo. The doses used in this study were 150 mg/kg daily for children weighing up to 40 kg or 4.69 grams/m2 for those weighing over 40 kg (104672).
• Juvenile idiopathic arthritis (JIA). Oral creatine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In children with JIA, taking a specific supplement (Kre-Celazine; All American Pharmaceutical) containing creatine and fatty acids 750 mg twice daily for 30 days may improve pain and inflammation when compared to baseline. Pain scores were reduced to 0 or 1 in 81% of these patients, and laboratory measures of inflammation were normalized in nearly every patient (90322). However, the effect of creatine alone in JIA patients is unclear. Also, the validity of this study is limited by a lack of control group.
• McArdle disease. It is unclear if oral creatine is beneficial for this condition. Details: There is some preliminary clinical evidence that taking creatine orally, 150 mg/kg daily for 5 days, followed by 60 mg/kg daily for 5 weeks, improves frequency and/or severity of muscle pain in some, but not all, patients with McArdle disease (70). However, continuing with the higher dose of 150 mg/kg daily throughout the 5-week period seems to INCREASE muscle pain and exercise intolerance (46564).
• Memory. It is unclear if oral creatine is beneficial for improving memory. Details: A meta-analysis of randomized controlled trials in healthy adults shows that taking creatine 2.2-20 grams orally for 5 days to 24 weeks improves performance on certain memory tests when compared with placebo (112202). However, the validity of this study is limited by high heterogeneity. In addition, the statistical methods utilized in this meta-analysis are likely to increase the risk of false positive results (112203) and re-analysis using other methods failed to reproduce the significant effects of creatine (112204).
• Mitochondrial myopathies. It is unclear if oral creatine is beneficial in patients with mitochondrial myopathies. Details: Preliminary studies using creatine orally for mitochondrial myopathies, such as chronic progressive external ophthalmoplegia and Kearns-Sayre syndrome, show mixed results. Using 150 mg/kg daily for 6 weeks or 20 grams daily for 4 weeks does not improve muscle function, exercise performance, or ease of completing activities of daily living when compared with placebo (46529,46650,104675). However, one very small clinical study shows that taking creatine 5 grams twice daily for 14 days, then 2 grams twice daily for 7 days, improves some measures of strength during high-intensity anaerobic and aerobic exercise, but not low-intensity exercise, when compared with baseline (4565).
• Multiple sclerosis (MS). It is unclear if oral creatine is beneficial in patients with MS. Details: A very small clinical study shows that taking creatine 20 grams orally daily for 5 days does not improve exercise capacity in people with relapsing-remitting multiple sclerosis when compared with placebo (46599).
• Muscle breakdown. It is unclear if oral creatine is beneficial for muscle breakdown prevention. Details: Preliminary clinical research shows that taking creatine 5 grams four times daily for 7 days seems to help maintain muscle mass and reduce loss of muscle strength associated with immobilization by a cast in young males aged 18-25 years (46713).
• Muscle cramps. It is unclear if oral creatine is beneficial in patients with muscle cramps related to hemodialysis. Details: Preliminary clinical research shows that taking creatine 12 grams orally 5 minutes before hemodialysis sessions for 4 weeks reduces the frequency of muscle cramps by around 60%, from an average of 6.4 episodes to 2.6 episodes over the course of 4 weeks of dialysis. No reduction in muscle cramp frequency is reported with placebo in these patients (46582).
• Muscular dystrophy. The evidence for the use of oral creatine in patients with various forms of muscular dystrophy is conflicting. Details: Preliminary studies have assessed oral creatine in patients with muscular dystrophy, including Duchenne dystrophy, Becker dystrophy, facioscapulohumeral dystrophy, sarcoglycan-deficient limb girdle muscular dystrophy, and myotonic dystrophies. Although a meta-analysis of available research shows that there is a small benefit of creatine on muscle strength in patients with muscular dystrophies, results of individual clinical trials have been inconsistent (104675). Some preliminary clinical research shows that measures of muscle strength or fatigue are improved after 8-16 weeks of treatment with creatine 3-5 grams or 0.1 gram/kg daily (6182,46596,46629,46739). Also, subjective improvement in muscle strength occurs in some people taking creatine 20 grams daily for one week, followed by 5 grams daily for 8 weeks (46639). The ability to perform activities of daily living improves only modestly, if at all (6182,46629,46739). Despite these positive results, some conflicting results exist. Some studies show no improvement in muscle strength or functional capacity with doses of 5 grams daily for 17-26 weeks (46616,46657), or 10.6 grams daily for 10 days followed by 5.3 grams daily for a total of 8 weeks (46587). Also, a dose of 10 grams daily for 12 weeks does not appear to improve muscle strength, although it seems to improve myalgia in some patients (10654). The inconsistent results reported in patients with muscular dystrophy may be explained by the different types of muscular dystrophies, the varied methodologies, or the small number of patients assessed. Studies failing to show an improvement with creatine may be underpowered, with sample sizes of only 20-60 (10654,46657).
• Neonatal apnea. It is unclear if oral creatine is beneficial for neonatal apnea treatment. Details: A preliminary clinical study shows that giving creatine orally 200 mg/kg daily for 2 weeks to premature infants with a gestational age of less than 32 weeks does not improve signs or symptoms of apnea of prematurity when compared with placebo (46623).
• Osteoarthritis. It is unclear if oral creatine is beneficial in patients with osteoarthritis. Details: In patients with osteoarthritis of the knee, preliminary clinical research shows that taking creatine 20 grams orally daily for one week, followed by 5 grams daily for 11 weeks, in combination with strengthening exercises, modestly improves physical functioning as measured by the number of stand-ups performed from a standard-height chair in 30 seconds when compared with exercise alone. Stiffness, pain, and quality of life were also improved with creatine supplementation; however, it is unclear if these improvements were significant when compared with exercise alone (46753).
• Parkinson disease. It is unclear if oral creatine is beneficial in patients with this condition. Details: Preliminary clinical research shows that taking creatine 5 grams twice daily for 12-18 months decreases the rate of disease progression when compared with placebo in patients who have not started conventional medications for symptom control (15353,46703). However, preliminary clinical research in patients with more advanced disease who have already started conventional medications shows that taking creatine 20 grams daily for 6 days followed by 2 grams daily for 6 months, and then 4 grams daily for 18 months does not decrease overall progression of symptoms or the need to start symptomatic treatment. However, increases in dopamine agonist doses were 3-fold lower over the course of the study in patients receiving creatine when compared with placebo (15354).
• Peripheral arterial disease (PAD). It is unclear if oral creatine is beneficial in patients with PAD. Details: A small clinical trial in patients with PAD shows that taking creatine monohydrate (Creapure, AlzChem Trostberg GmbH) 5 grams four times daily for one week, followed by 5 grams daily for the next 7 weeks, does not improve functional capacity based on walking distance, upper body strength, or lower body strength, when compared with placebo (108337). This study may have been inadequately powered to detect differences between groups.
• Physical performance. It is unclear if oral creatine is beneficial for improving physical performance in older patients and those at risk for functional disability. Details: A meta-analysis of 15 clinical studies in healthy older adults and adults of any age with chronic disease who are at risk for functional disability shows that taking oral creatine, usually at a dose of 5 grams daily, for 5 days to 32 weeks, improves lower extremity physical function, upper limb and hand strength, and lean tissue mass when compared with control. Taking creatine does not improve lower limb strength, functional mobility, walking time, or aerobic capacity. Subgroup analyses suggest that improvements are greater with an extended duration of creatine use. Additionally, combining creatine with resistance training may increase benefits for lower extremity physical function, upper body strength, and lean tissue mass (115978). The heterogeneity of the included patient populations limits the practical applicability of these findings.
• Post-stroke fatigue. It is unclear if oral creatine is beneficial in patients with post-stroke fatigue. Details: Very preliminary clinical research in patients undergoing progressive resistance training after a stroke shows that taking a specific creatine supplement (Creapure, AlzChem Trostberg GmbH) 0.3 grams/kg orally daily for 7 days, followed by 0.1 grams/kg orally daily for a total of 10 weeks modestly improves 6-minute walk test distance when compared with placebo (112207).
• Postoperative recovery. Small clinical studies suggest that oral creatine may not improve recovery of muscle strength after knee surgery. Details: Preliminary clinical research shows that taking creatine 20 grams daily for 7 days, followed by 5 grams daily for 11 weeks, does not improve recovery of muscle strength after anterior cruciate ligament (ACL) reconstruction surgery in young adults when compared with placebo (46622). Other preliminary research shows that taking creatine 10 grams daily for 10 days before total knee arthroplasty, followed by 5 grams daily for 30 days after surgery, does not improve muscle strength or functional recovery when compared with placebo (46659). These studies are limited by small size and variability in patient population and supplementation regimen.
• Rett syndrome. It is unclear if oral creatine is beneficial in patients with this condition. Details: Preliminary clinical research shows that taking creatine 200 mg/kg daily for 6 months does not improve symptom scores when compared with placebo in patients aged 3-25 years with Rett syndrome (46759).
• Rheumatoid arthritis (RA). Oral creatine does not seem to improve disease activity in patients with RA, but it might improve muscle strength. Details: Clinical research in adults with RA shows that taking creatine increases lean muscle mass, total body mass, and muscle strength, but does not alter disease activity or improve strength or physical function, when compared with placebo or a control group (6929,95964). Creatine was taken as 5 grams four times daily for 5 days, followed by 3 grams daily for 12 weeks, in one study and 5 grams four times daily for 5 days, followed by 0.5 grams four times daily for 16 days, in the other study (6929).
• Schizophrenia. It is unclear if oral creatine is beneficial in adults with schizophrenia. Details: Preliminary clinical research shows that taking creatine orally, 3 grams daily for one month followed by 5 grams daily for 2 months, does not improve symptom control or cognitive function in adults with schizophrenia when compared with placebo (16390).
• Sleep deprivation. It is unclear if oral creatine is beneficial in adults who are subjected to sleep deprivation. Details: A small crossover study in healthy adults aged 20-28 years shows that taking a single oral dose of creatine 0.35 g/kg prior to sleep deprivation attenuates fatigue and cognitive decline over the next 7 hours when compared with placebo (115979).
• Spinal cord injury. It is unclear if oral creatine is beneficial in patients with spinal cord injury. Details: Preliminary clinical research shows that taking creatine orally, 20 grams daily for 7 days, increases exercise capacity by improving respiratory function in patients with spinal cord injury (cervical level C5-7) when compared with placebo (46563). However, other preliminary clinical research shows that patients with similar injuries taking creatine 10 grams twice daily for 6 days, followed by 5 grams daily, do not have significant improvements in wrist muscle or hand function (46660).
• Spinal muscular atrophy. It is unclear if oral creatine is beneficial in patients with spinal muscular atrophy. Details: Preliminary clinical research shows that children with type II or III spinal muscular atrophy do not benefit from taking creatine orally for 6 months (46841). Doses were 2 grams daily for children aged 2-5 years, and 5 grams daily for children aged 5-18 years.
• Traumatic brain injury (TBI). It is unclear if oral creatine is beneficial in children with a TBI. Details: In children and adolescents who have suffered a TBI, preliminary clinical research shows that taking creatine orally 0.4 grams/kg daily for 6 months reduces the duration of post-traumatic amnesia by 60 days. It also reduces the risk of headache by 88%, fatigue by 87%, and dizziness by 80% when compared with control. There is also a trend towards reduced duration of intubation and total time in the intensive care unit or hospital (46694). More evidence is needed to rate creatine for these uses.

(Read more about CREATINE)

EFFECTIVE

• Folate deficiency. Oral or intravenous folic acid is effective for the prevention or treatment of folate deficiency. Details: Administering folic acid orally or parenterally improves and prevents folate deficiency (505,8739). Clinical research shows that supplementation with folic acid 100 mcg to 5 mg daily during pregnancy decreases the risk of developing megaloblastic anemia by up to 79% (91307).

LIKELY EFFECTIVE

• Kidney failure. Taking folic acid orally reduces homocysteine levels in people with kidney failure who are on hemodialysis. Details: Over 85% of people with kidney failure have hyperhomocysteinemia. Treatment of hyperhomocysteinemia in kidney failure is often more difficult than with normal kidney function (1489,3324,7289,9413,9414,9416). The reasons for this are not fully understood; renal uptake and metabolism of homocysteine may be reduced in severe kidney failure, and hemodialysis may contribute to vitamin deficiencies (6884,9414,9417). Folic acid 0.8-15 mg daily or 3 times weekly is generally used, but the degree of homocysteine reduction varies between 12% to 50%, and normal homocysteine levels (less than 12 µmol/L) cannot always be achieved. Adding vitamin B12 400-1000 mcg daily and vitamin B6 20-50 mg daily produces an additional reduction in homocysteine (1489,6884,7289,7881,9322,9413,9414,9415,9416,9417). Folic acid doses greater than 15 mg daily do not seem to provide additional benefit. Also, doses of 30-60 mg might cause a rebound in homocysteine levels when treatment is stopped (9219). Despite the homocysteine-lowering effect of folic acid in kidney failure, the most robust meta-analysis of 11 clinical trials suggests that folic acid supplementation does not seem to reduce the risk of cardiovascular events (50527). A smaller meta-analysis of 7 clinical trials that used a different primary composite outcome suggests that folic acid might reduce the risk of cardiovascular events by 15% when compared with control (91311). There has also been interest in using a reduced form of folic acid, L-5-methyltetrahydrofolate (L-5-MTHF). One study in patients on hemodialysis suggests that taking L-5-MTHF 17 mg daily for 12 weeks might lower homocysteine levels to a greater extent than an equimolar 15 mg of folic acid (104908). Another clinical trial in patients on hemodialysis suggests that giving intravenous L-5-MTHF 50 mg three times weekly is associated with an increased survival of about 36 months, compared with about 26 months with folic acid 5 mg daily. There was no difference in homocysteine reduction between groups (104909). These results should be interpreted with caution because they have not been replicated, and there was no placebo control. Furthermore, survival may have been affected by the availability of kidney transplants.
• Hyperhomocysteinemia. Oral folic acid, taken alone or in combination with other B vitamins, lowers homocysteine levels in most patients. However, it is unclear if this has cardiovascular benefits. Details: Taking folic acid orally 0.4-5 mg daily lowers fasting homocysteine levels by 20% to 30% in people with normal to moderately elevated homocysteine levels at baseline. Folic acid 0.8-1 mg daily seems to provide maximal reduction (9307,9400,9401,9405,9408,11337,11338,50145). Doses above 1 mg daily do not seem to add benefit (9307), except in some people with certain gene mutations that cause homocysteine levels of 20 µmol/L or higher (9408). The higher the initial homocysteine levels, the lower the folic acid dose needed to attain maximum homocysteine reduction (9307). The effects of folic acid supplementation on homocysteine concentrations appear to be greater in females than males (50145). Adding vitamin B6 25-250 mg or vitamin B12 500 mcg seems to further reduce homocysteine levels (1489,9400,9405,9406,9408,107136). Some experts recommend routine use of vitamin B12 in homocysteine-lowering regimens to avoid the risk of neuropathy in people with undetected vitamin B12 deficiency (9405). Increasing folic acid intake with supplements or folate-fortified cereal products is more effective for reducing homocysteine levels than increasing intake of folate-rich foods (6367). Fortification of cereals and flour with 140 mcg folic acid per 100 grams reduces the mean homocysteine level in the general population by about 7% (7881,9404,9407). Elevated homocysteine levels are considered by some to be an independent risk factor for atherosclerosis progression, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, ischemic stroke, and other vascular complications (3886,3887,6236,7725,9314,9318,50509). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). Although folic acid lowers homocysteine levels, it is not yet known whether this reduces the risk of vascular disease. One meta-analysis shows that taking folic acid can reduce the risk of stroke by about 10% in patients with cardiovascular disease (CVD); the reduction is greatest in patients for whom homocysteine levels are lowered by at least 25% (96157). A meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation, including folic acid, reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136). However other research does not agree. Meta-analyses of clinical research show that folic acid does not prevent CVD or coronary heart disease, in spite of lowering homocysteine by up to 55%, when individuals with normal or high levels of homocysteine are considered (50539,96147,97619). Furthermore, most research shows that folic acid supplementation, alone or in combination with vitamin B6 and vitamin B12, does not improve endothelial function or improve secondary prevention of cardiovascular events such as myocardial infarction in people with existing CVD despite a homocysteine-lowering effect (9313,11337,11387,13482,50437,97619). Some research even suggests an increase in CVD risk concurrent with homocysteine lowering (13482). Large randomized controlled trials are needed to confirm or refute these findings. Some researchers hypothesize that different genetic profiles might explain some of these conflicting results. For instance, individuals with a homozygous 677TT MTHFR genotype typically have increased homocysteine levels. However, a meta-analysis suggests that treatment with folic acid does not reduce the risk of ischemic heart disease despite reducing homocysteine levels in individuals with 677TT MTHFR (50456). It has also been theorized that a reduced form of folic acid, 5-methyltetrahydrofolate (5-MTHF) might work better in these individuals. Although [6RS]-5-MTHF has been shown to lower homocysteine levels (104915), studies assessing its cardiovascular benefits are lacking.
• Methotrexate toxicity. Oral folic acid reduces the severity of methotrexate toxicity. Details: Oral folic acid reduces methotrexate toxicity symptoms, such as nausea and vomiting, in the treatment of rheumatoid arthritis (RA) and psoriasis (768,2162,2163,2164,4492,4493,4494,9369,9419). Folic acid also seems to reduce methotrexate-induced hepatic side effects by approximately 36% (50320). Some research shows that a low, 0.8 mg weekly dose of folic acid is equally effective to a higher dose of 5 mg weekly for the prevention of methotrexate toxicity (102388).
• Neural tube birth defects. Oral folic acid helps to prevent neural tube birth defects in newborns. Details: Clinical practice guidelines recommend that anyone capable of becoming pregnant take folic acid 400 mcg daily from fortified foods or supplements to prevent neural tube birth defects in infants. Folic acid 600 mcg daily is advised during pregnancy (94811,96146). This recommendation is based on research showing that a higher intake of folic acid from food and supplements during pregnancy reduces the primary incidence of neural tube birth defects by 41% to 69% (3325,9309,50344,50403,50468,95156). Individuals with a history of children with neural tube birth defects usually take a higher dose of folic acid 4000 mcg daily starting one month before and continuing for up to 3 months after conception (96146). Evidence shows that, when used for secondary prevention, folic acid supplementation reduces the incidence of neural tube defects by 66% to 87% (21235,50263,50344,50403,95156). In the US, foods containing at least 60 mcg of folic acid can be labeled with a health claim stating that healthful diets with adequate folic acid intake may reduce the risk of having a child with a brain or spinal cord defect (102369).

POSSIBLY EFFECTIVE

• Cognitive impairment. Taking folic acid alone, with other B vitamins or with docosahexaenoic acid (DHA), might improve thinking and memory skills in older patients with cognitive impairment. Details: One clinical trial in patients aged 65 years and older with mild cognitive impairment (MCI) shows that taking folic acid 400 mcg daily for 2 years increases IQ scores when compared with placebo (100952). Two small, low-quality clinical studies in patients aged 70-90 years with cognitive impairment and low folate levels or folate deficiency shows that taking folic acid 5 or 15 mg daily for up to 63 days improves cognitive function, including measures such as memory and attention, when compared with placebo or baseline (50301,104911). Folic acid also appears to be beneficial when used in combination with other B vitamins or with DHA. A clinical trial in patients aged 70 years and older with MCI shows that taking folic acid 800 mcg, vitamin B6 20 mg, and vitamin B12 500 mcg daily for 2 years mitigates decline in executive function and, in patients with high baseline homocysteine levels, improves cognition and memory when compared with placebo (50480). Taking folic acid 800 mcg with or without DHA 800 mg daily for 6 months modestly improves cognition, as measured on the full-scale intelligence quotient, when compared with placebo (103978,109196). However, this benefit is no longer present at 6 months after treatment discontinuation (109196).
• Depression. Oral folic acid seems to modestly reduce depression severity when added to conventional antidepressant therapy. It is unclear if folic acid can reduce the prevalence of depression or the risk for suicide. Details: Observational studies suggest that depression is correlated with low folate status, particularly in females (50105,50127,50243). Taking folic acid 0.2-15 mg daily for up to 6 months with conventional antidepressants seems to improve treatment response in patients with major depressive disorder (3657,10884,10887,50566,109190). One meta-analysis shows that taking L-methylfolate or folic acid as an adjunct to treatment with conventional antidepressants modestly reduces depression severity when compared with placebo and conventional antidepressants. The response and remission rates were improved by 36% and 39%, respectively (109190). However, limited clinical research suggests that folic acid is not effective as a replacement for conventional antidepressant therapy (10886). Also, a small clinical study in adolescents at high familial risk for mood disorders suggests that taking folic acid 2.5 mg daily for up to 36 months does not prevent mood disorders when compared with placebo. However, in the patients that were eventually diagnosed with depression, the time of onset was delayed from 5 months to 15.5 months in the group using folic acid when compared with placebo (91313). Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that folic acid is not currently recommended as monotherapy treatment for unipolar depression (110318). Observational research has also evaluated the association between folic acid supplementation and suicidal events in patients with or without depression. One within-person cohort study, in which only 12% of patients were diagnosed with depression, has found that filling a folic acid prescription of 0.4-5 mg daily, either alone or as part of a multivitamin, is associated with a reduced risk for suicidal events during the following months when compared with months without a prescription (109201). It is unclear what percentage of these patients, if any, had folate deficiency at baseline.
• Hypertension. Oral folic acid seems to modestly reduce hypertension. Details: A meta-analysis of clinical research shows that taking folic acid 5-10 mg daily for at least 6 weeks reduces systolic blood pressure by 2mmHg and improves flow-mediated dilation by 1.6% in hypertensive individuals (50364). Some research has evaluated folic acid in hypertensive patients when used with antihypertensive drugs. Results show that taking folic acid 400-800 mcg in combination with enalapril 10 mg daily for about 4.5 years does not improve blood pressure when compared with enalapril alone (50302,96158). However, in hypertensive patients with heavy proteinuria, this combination seems to reduce the risk of all-cause mortality by about 41% when compared with enalapril alone (96158).
• Phenytoin-induced gingival hyperplasia. Topical folic acid seems to reduce gingival hyperplasia due to phenytoin. The effect of oral folic acid is unclear. Details: Applying folic acid topically seems to inhibit gingival hyperplasia secondary to phenytoin therapy (2151). However, taking folic acid orally does not seem to improve gingival hyperplasia secondary to phenytoin therapy in adults (2150,2151,2152), although some evidence suggests that taking folic acid 500 mcg daily reduces the risk of phenytoin-induced gingival hyperplasia by 33% in children when compared with placebo (50463).
• Stroke. Although some clinical research has shown that oral folate reduces stroke risk by a small amount, more research is needed to determine who is most likely to benefit. Most individual clinical trials show that folic acid seems to reduce stroke risk only in regions without food-fortification policies. Details: Multiple clinical studies have shown that folic acid supplementation reduces the risk of stroke by 10% to 25% in regions WITHOUT established policies mandating folic acid fortification of grain products (50240,50485,50525,50539,91325,96154,96157,96159,97308). The effect appears to be greatest when folic acid is taken in low doses (usually 0.8 mg daily or lower) (50525,96157,96159), in regions with a low prevalence of statin use (50525,96159), in patients with high cholesterol levels at baseline (96152), in patients who achieve homocysteine reduction of at least 20% (50407,96157), and in patients with the lowest folate levels at baseline (96154,96157). There is also some evidence that the effect of folic acid on stroke risk is greatest in patients with low baseline levels of vitamin B12 (96159). In 2001, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Most research shows that folic acid supplementation does not reduce the risk of stroke in regions WITH established policies mandating folic acid fortification (50240,50485,50525,50539,96157,96159,97308). However, there is some evidence that folic acid may reduce the risk of stroke in patients from regions with folic acid fortification who have recently had a stroke or transient ischemic attack and are not using antiplatelet drugs (90379). Meta-analyses of clinical research have been conducted. However, possible confounding due to the presence or absence of folic acid fortification is unclear. A meta-analysis of the available research in adults with existing CVD shows that folic acid supplementation at a daily dose of less than 2 mg reduces the risk for stroke by about 10% (102386). Also, a meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation, including folic acid, reduces the relative risk of stroke by 10% when compared with placebo (97619). In patients with a history of stroke, a meta-analysis shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136). It is unclear if folic acid reduces the stroke risk in patients with impaired kidney function. Some research shows that taking folic acid in combination with high doses of vitamin B12 (cyanocobalamin) does not reduce the risk of stroke in these patients (11387,96150). However, there is concern that the lack of benefit may have been due to the decline in kidney function from high doses of cyanocobalamin (96150). Additional research is needed to determine if folic acid supplementation is beneficial in patients with impaired kidney function when used with other forms of vitamin B12 such as methylcobalamin or hydroxycobalamin.
• Vitiligo. Oral folic acid seems to improve vitiligo symptoms. Details: Taking folic acid orally seems to improve symptoms of vitiligo (2153,2154). This finding is supported by a meta-analysis of observational research which shows that patients with vitiligo have higher serum homocysteine levels when compared with patients without vitiligo (100951).

POSSIBLY INEFFECTIVE

• Anemia. Adding oral folic acid to oral iron therapy does not seem to improve hematologic parameters in patients with anemia. Details: In postpartum patients with anemia, clinical research shows that taking iron as ferrous fumarate 600 mg and folic acid 1 mg daily is no more effective than iron alone for improving hemoglobin status (91319). Also, clinical research in non-pregnant menstruating females shows that taking folic acid 0.4 mg daily or 2.8 mg once weekly for 16 weeks with iron 60 mg daily does not reduce anemia or improve iron status when compared with iron alone (109193). During pregnancy, clinical research shows that folic acid supplementation does not decrease the risk of pre-delivery anemia or low hemoglobin levels (91307).
• Age-related cognitive decline. Oral folic acid does not seem to prevent cognitive decline in healthy elderly adults. Details: Most clinical research shows that taking folic acid, alone or in combination with other B vitamins, does not improve cognitive function, including memory, language, or executive function, in elderly adults with age-related cognitive decline (50318,50412,50510). In fact, a large-scale observational study in the US has found that people over 65 years of age who consume large amounts of folic acid (median of 742 mcg daily) have cognitive decline at a rate twice as fast as those consuming smaller amounts (median of 186 mcg daily) (13068). While most research on folic acid for age-related cognitive decline lacks positive findings, many of the studies are small, short-term (<1 year), underpowered to detect significant differences, and not specific to patients with high homocysteine levels. Population research has found that high homocysteine levels are associated with decreased cognition in older adults, suggesting that using folic acid to lower homocysteine levels might mitigate cognitive decline in these patients (50094). Two long-term clinical trials examining the effects of folic acid in elderly adults with high homocysteine levels show mixed results. A large-scale clinical trial of patients aged 50-70 years from the Netherlands who have high homocysteine levels shows that taking folic acid 800 mcg daily for 3 years increases memory, information processing, and other measures of cognitive function when compared with placebo (15271). However, another large-scale clinical trial of patients aged 65 years and older from the Netherlands who have high homocysteine levels shows that taking folic acid 400 mcg and vitamin B12 500 mcg daily for 2 years lowers homocysteine levels, but does not appear to improve overall measures of cognitive function, when compared with placebo (90392). The reasons for the discrepant findings in these two studies are not clear but might relate to differences in the dose of folic acid, duration of treatment, and age of patients included.
• Cataracts. Oral folic acid does not seem to reduce cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or with risk factors for CVD shows that taking folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of developing cataracts. Furthermore, the risk of cataract extraction was increased by 28% in these patients (96149).
• Diarrhea. Oral folic acid does not seem to reduce the risk of diarrhea, and might even increase the incidence of diarrhea in children. Details: In children aged 6-30 months at risk of malnourishment, clinical research shows that taking a nutritional supplement (Nutriset Ltd) enriched in folic acid 75-150 mcg, with or without vitamin B12 0.9-1.8 mcg, daily for 6 months does not reduce the incidence of diarrhea when compared with placebo. Enrichment with folic acid, with or without vitamin B12, actually seems to increase the likelihood of having more episodes of both persistent diarrhea and diarrhea lasting over 3 days (90391).
• Fall prevention. Oral folic acid does not seem to reduce the risk of falls. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg daily, for 2 years, does not prevent falls when compared with placebo in elderly individuals also taking vitamin D (96148).
• Fetal and premature infant mortality. Oral vitamin B12 does not seem prevent mortality in premature infants. Details: Clinical research shows that supplementation with folic acid during pregnancy does not decrease the risk of miscarriage, stillbirth, or neonatal death (91307,96156).
• Leukemia. Oral vitamin B12 does not seem to reduce the risk for pediatric acute lymphoblastic leukemia. Details: A meta-analysis of results from two case-control studies has found that increased folate intake during pregnancy is not associated with a reduced risk of childhood acute lymphoblastic leukemia (50247).
• Male infertility. Oral folic acid does not seem to improve sperm parameters or pregnancy rates in males with infertility. Details: Some small clinical studies show that taking folic acid, alone or with zinc, increases sperm count in males with idiopathic infertility or in males with a grade III varicocele (9334,90194). However, another small study in males with asthenozoospermia shows that taking folic acid 5 mg, selenium 200 mcg, and vitamin E 400 IU daily for 3 months does not improve sperm parameters when compared with placebo (104907). Furthermore, there seems to be no improvement in clinical outcomes. One large, high-quality clinical study in males with idiopathic infertility shows that taking folic acid 5 mg with zinc 30 mg daily for 6 months does not improve sperm morphology, pregnancy rate, or live birth rate when compared with placebo (102085). Folic acid has also been evaluated in combination with other ingredients. A retrospective study in males with or without varicocele-related infertility suggests that taking a specific combination product containing folic acid 0.2 mg, vitamin C, zinc, L-carnitine fumarate, acetyl-L-carnitine, coenzyme Q10, selenium, and vitamin B12 (Proxeed Plus, Sigma-Tau) twice daily for 6 months is associated with improvements in sperm count, sperm concentration, and sperm motility when compared to baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles (111296). The validity of this study is limited by the lack of a comparator group.
• Osteoporosis. Oral folic acid does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in elderly adults or adults with a history of cerebrovascular disease shows that taking vitamin B12 500 mcg and folic acid 0.4-2 mg, with or without vitamin B6 25 mg, daily for 2-3 years does not seem to reduce the risk for osteoporotic fractures when compared with placebo (90377,90393). A 5-7 year follow-up of this research has also found no benefit (103981).
• Physical performance. Oral folic acid does not seem to improve physical performance in older adults. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg daily for 2 years, does not improve hand strength or improve performance such as walking when compared with placebo in elderly individuals also taking vitamin D (96148).
• Pre-eclampsia. Oral folic acid does not seem to prevent pre-eclampsia in pregnant patients. Details: While the effect of low-dose prenatal folic acid is unclear, high-dose folic acid does not seem to reduce the risk of pre-eclampsia. Some population research has found that low-dose folic acid is associated with a 22% reduced odds of pre-eclampsia, while other research has found no association (91308,99370,99372,110447). A large clinical trial evaluating high-dose folic acid in pregnancies at risk for pre-eclampsia shows that taking 4 mg daily, starting at 8-16 weeks of gestation and continuing until delivery, does not reduce the risk of pre-eclampsia when compared with placebo (103929). A secondary analysis of this study in twin pregnancies has also found no benefit with high-dose folic acid supplementation (103977).
• Respiratory tract infections. Oral folic acid does not seem to prevent respiratory tract infections. Details: Clinical research in children aged 6-30 months at risk of malnourishment shows that taking a nutritional supplement (Nutriset Ltd) enriched in folic acid 75-150 mcg, with or without vitamin B12 0.9-1.8 mcg, daily for 6 months does not reduce the incidence of lower respiratory infections when compared with a supplement not enriched with folic acid and vitamin B12 (90391).

LIKELY INEFFECTIVE

• Colorectal adenoma. Oral folic acid does not prevent colorectal adenomas. Details: Although some population research and one clinical study has found that high folate intake is associated with reduced colorectal adenoma risk (2142,2143,91303), most clinical research does not support this finding. Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily for up to 9.2 years, does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389). Other clinical research suggests that taking folic acid does not reduce the occurrence or recurrence of adenomas or incidence of advanced adenomas (34596,50241,50265,50369,50394,50449,50522). Furthermore, treatment with folic acid for more than 3 years seems to be associated with an increased risk of advanced adenomatous lesions (50378).
• Fragile X syndrome. Oral folic acid does not improve symptoms in children with fragile X syndrome. Details: Clinical research shows that taking folic acid orally does not improve symptoms of fragile X syndrome (2155,2156,2157,2158,2159,2160,50575).
• Preterm labor. Oral folic acid does not seem to reduce the risk of preterm birth. Details: Meta-analyses of clinical research show that supplementation with folic acid 200 mcg to 5 mg during pregnancy does not decrease the risk of preterm birth (91307,96155). An observational study in patients with and without epilepsy found that folic acid supplementation during pregnancy was associated with a lower odds of preterm birth in patients receiving antiseizure medications; however, no link between folic acid and preterm labor was reported in patients without epilepsy or in those with epilepsy not receiving antiseizure medications (110447).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Abdominal wall defects. It is unclear if oral folic acid helps to prevent abdominal wall defects in newborns. Details: Observational research in a population in northern China has found that taking folic acid supplements until the end of the first trimester modestly reduces the risk of abdominal wall defects and the risk of omphalocele, specifically, in the newborn when compared with not taking folic acid. However, this association was not found in a population in southern China (109191). These differing outcomes may be related to the lower dietary folate intakes in northern China.
• Acne. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing folic acid, vitamin B6, nicotinamide, azelaic acid, zinc, and copper for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared with baseline (90800).
• Age-related macular degeneration (AMD). Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily reduces the risk of developing AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to folic acid, other ingredients, or the combination.
• Age-related testosterone deficiency. Folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in males with overweight or obesity, mild erectile dysfunction, and normal to low androgen levels shows that taking a combination product containing folic acid 400 mcg, alpha-lipoic acid, myo-inositol, and apple (Sinopol Forte) increases testosterone, luteinizing hormone, and measures of erectile dysfunction but not follicle-stimulating hormone or sperm parameters when compared to baseline (111674). The validity of these effects is limited by the small sample size and the lack of a comparator group, and it is unclear if these effects are due to folic acid, other ingredients, or the combination.
• Alzheimer disease. It is unclear if oral folic acid reduces the risk of developing this condition. Details: Low levels of folate and high levels of homocysteine have been linked to a greater risk of Alzheimer disease (50094). Also, some observational studies have found that higher intake of folate from the diet and supplements in elderly adults is associated with a reduced risk of developing Alzheimer disease when compared with lower intake (13165,15270). One small clinical trial in patients with Alzheimer disease who are taking cholinesterase inhibitors shows that taking folic acid 1 mg daily for 6 months increases the likelihood of treatment response, classified as global improvement in behavioral and/or functional status with no decline in mental status scores, by 78% to 87% when compared with placebo (50246). Also, preliminary clinical research in patients with probable Alzheimer disease who are not consuming a folate-fortified diet shows that taking vitamin B12 50 mcg daily plus folic acid 1.2 mg daily for 6 months modestly improves some measures of cognitive performance and decreases levels of homocysteine when compared with placebo (107150). However, not all research agrees. Clinical research in patients with probable Alzheimer disease using routine medications shows that taking folic acid 5 mg, vitamin B12 1 mg, and vitamin B6 25 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo (50319). However, all patients in this study were also consuming a folate-fortified diet.
• Angioplasty. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that folic acid 1 mg, vitamin B12 400 mcg, and pyridoxine 10 mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6, and vitamin B12 followed by oral administration of folic acid 1.2 mg, vitamin B6 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151).
• Atopic dermatitis (eczema). It is unclear if oral folic acid during pregnancy reduces the risk of eczema in the child. Details: Observational research has found that consuming both iron and folic acid supplements during pregnancy is associated with a four-fold reduced risk for developing atopic dermatitis in the child. However, use of either iron or folic acid supplementation alone is not associated with an effect on the child's risk for atopic dermatitis (102387).
• Autism spectrum disorder. It is unclear if oral folic acid intake during pregnancy reduces the risk of autism spectrum disorder in the child. Details: A meta-analysis of population research has found that consumption of folic acid of at least 400 mcg daily from both diet and supplements during pregnancy is associated with a 45% reduced risk of autism in the child at 2-15 years of age. Also, supplementation with folic acid during the prenatal to early period of pregnancy is associated with an approximate 43% reduced risk of autism in the child. This association did not differ between countries with or without a folate fortification program (109198). An individual population study has also found that prenatal folic acid supplementation initiated the first day of the last menstrual period before conception is associated with a 39% reduced odds of autism in the child at age 3.3-10.2 years when compared to pregnancies without folic acid supplementation (91324).
• Beta-thalassemia. There is limited evidence on the oral use of folic acid for beta-thalassemia minor. Details: Patients with beta-thalassemia minor may experience decreased muscle strength and increased bone or muscle pain. A small clinical study in children with this condition shows that taking folic acid 1 mg, with or without L-carnitine 50 mg/kg, daily for 3 months reduces bone pain by 64% to 84% and increases the number of stairs climbed by 2- to 5-fold when compared with baseline (90631). The validity of this finding is limited by the lack of a control group.
• Bipolar disorder. It is unclear if adding oral folic acid to conventional bipolar therapy further improves symptoms. Details: Some clinical evidence suggests that folic acid does not improve the antidepressant effects of lithium in patients with bipolar disorder (50566). However, other clinical evidence suggests that taking folic acid in combination with valproate during the acute phase of mania improves the effects of valproate (50357).
• Breast cancer. It is unclear if oral folic acid reduces breast cancer risk. Details: Some older population research suggests that increased intake or levels of folic acid alone does not affect the risk of breast cancer or breast cancer-related mortality (50218,50224). However, in a specific group of women who also consume high amounts of dietary methionine, cyanocobalamin (vitamin B12), or pyridoxine (vitamin B6), dietary intake of folate is associated with a reduced risk of breast cancer (9328,50224). Also, more recent population research has found that folic acid plus folate dietary intakes between 153-400 mcg are associated with a reduced risk of breast cancer. This risk is further reduced in those who drink relatively large amounts of alcohol (90794). Folate intakes greater than 400 mcg daily do not appear to be protective against breast cancer (90794).
• Cancer. It is unclear if oral folic acid prevents cancer. Details: A large cohort study of children born to mothers with epilepsy on antiseizure medications suggests that prenatal folic acid exposure of 1 mg daily or more, at an average of 4.3 mg daily, is associated with a 2.7-fold greater risk of pediatric cancer when compared with children born to mothers with epilepsy but without prenatal exposure to high-dose folic acid. Additionally, this risk is not present in children of mothers without epilepsy taking high-dose folate (112103). It is unclear how maternal epilepsy, antiseizure medications, and folate interact to increase the risk of pediatric cancers. However, in the absence of clear guidelines, mothers with epilepsy should take no more than 4 mg of folic acid daily (112101,112102).
• Cardiovascular disease (CVD). Although oral folic acid does not seem to prevent most CVD events, some research suggests that increased dietary folic acid might lower the risk of stroke and CVD-related mortality in patients at high risk for CVD. Details: In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Meta-analyses of available research show that folic acid might lower the risk of stroke in patients with CVD (97619,102386,107136). Some clinical research shows that taking folic acid reduces the risk of CVD by 15% in patients with kidney failure or chronic kidney disease (50444,91311). However, most research shows that folic acid supplementation, alone or in combination with vitamin B6 and vitamin B12, does not improve endothelial function or reduce the risk of death or CVD events in patients with existing hyperhomocysteinemia, coronary heart disease, CVD, kidney disease, or prior stroke, despite having a homocysteine-lowering effect (9313,9322,11337,11387,13482,50437) (50512,50527,96154,96147,97619,102386). Some population research has evaluated adults at high risk for CVD. This research has found that dietary folate intake of at least 382 mcg daily is associated with a modest reduction in CVD-related mortality and possibly all-cause mortality. Consuming folic acid as a component of fortified food in doses of more than 251 mcg daily is associated with a modest reduction in CVD-related mortality. Conversely, folic acid supplementation is associated with a higher risk of CVD and overall mortality, and there is a J-shaped association between folate intake, serum folate levels, and red blood cell folate levels, with both CVD-related and all-cause mortality (109199).
• Cervical cancer. It is unclear if oral folic acid prevents cervical cancer. Details: Epidemiological evidence has found that increasing folate intake from dietary and supplement sources, along with thiamine, riboflavin, and vitamin B12, might decrease the risk of precancerous cervical lesions (11074).
• Child development. It is unclear if oral folic acid supplementation during pregnancy improves child development. Details: Clinical research in Northern Ireland shows that taking folic acid 400 mcg daily starting in the 14th week of gestation and continuing until the end of pregnancy improves word reasoning in the child at 7 years of age when compared with placebo. When compared with a historical cohort from Britain, folic acid supplementation was associated with an increase in full scale IQ, verbal IQ, performance IQ, and general language at 7 years of age (102385). At age 11, benefits in word reasoning were no longer significant. However, there were modest benefits in some measures of processing speed when compared with placebo. Verbal comprehension was modestly improved in females, but not males (109192). Observational research in pregnant individuals and their children in Spain has found that taking less than 400 mcg of folic acid daily during pregnancy is associated with lower mental alertness scores in children at ages 7-9 years when compared with folic acid 400-999 mcg daily, while taking folic acid 1000 mcg or more daily during pregnancy was associated with improvements in some measures of working memory in the children. However, no relationship between folic acid dosing and most other measures of cognitive function was identified (110449).
• Chronic fatigue syndrome (CFS). Although there is interest in using oral or injectable folic acid for CFS, there is insufficient reliable information about the clinical effects of folic acid for this condition.
• Chronic kidney disease (CKD). While adding oral folic acid to enalapril might slow CKD progression, adding folic acid to high-dose vitamin B12 does not seem to be beneficial. Details: Clinical research in adults with hypertension and CKD shows that taking enalapril with folic acid 800 mcg for a median of 4.4 years reduces the risk of worsening kidney function by 21% and slows the rate of kidney function decline by 44% when compared with enalapril alone (96153). However, clinical research does not support the use of folic acid in patients with CKD when used in combination with high-dose vitamin B12 (cyanocobalamin). Vitamin B12 might increase the risk of negative outcomes (50253,50409,96150). More research is needed to determine the benefits of folic acid when used alone.
• Colorectal cancer. It is unclear if oral folic acid prevents colorectal cancer. Details: Although the majority of population research suggests that taking folic acid orally from dietary and supplemental sources reduces the risk of colorectal cancer (505,2140,2144,2145,2250,6271,9325,9326,50109,50427,50450)(91306,91323,96160,109188,110450), clinical evidence in general is not supportive. Most clinical research and meta-analyses of clinical trials suggest that taking folic acid from dietary or supplemental sources does not reduce the risk of colorectal cancer (2141,34596,50394). The reason for this discrepancy is unclear. Some observational research suggests that an inverse association between folate intake and risk of colorectal cancer was not apparent until at least 12 years after baseline folate intake was determined (109188). A meta-analysis of observational studies suggests that the benefits of folic acid supplementation on colorectal cancer risk might be limited to patients with moderate to high alcohol consumption (110450). Other clinical evidence suggests that the beneficial effect of folic acid may be limited to colon, but not rectal, cancer (21501). Furthermore, the beneficial effect for colon cancer may be limited to only certain subtypes. For instance, females with folate intake of at least 400 mcg daily seem to have a 46% reduction in the risk of p53-overexpressing colon cancer, but not p53-negative tumors, when compared with those who consume less than 200 mcg daily (21300). Also, the source of folic acid may influence its effects. Some observational research suggests that dietary folate, but not folic acid supplementation, reduces the risk of colon cancer (21501).
• Congenital heart disease. It is unclear if oral folic acid prevents congenital heart disease. Details: The exact cause of congenital heart disease is unknown but is thought to be a combination of genetic and environmental factors. Population research has found that supplementation with folic acid or folic acid-containing prenatal vitamins during pregnancy is associated with up to a 40% lower risk of congenital heart defects in newborns (99373).
• Dementia. It is unclear if oral folic acid is beneficial for the prevention or treatment of dementia. Details: While some preliminary research shows that folic acid might aid in the prevention and treatment of Alzheimer disease (13165,15270,50246,90374), two small clinical trials show that taking folic acid 15-20 mg daily for 10-12 weeks does not seem to improve cognitive function or the severity of dementia in patients with various forms of dementia, including vascular dementia, Lewy body dementia, probable Alzheimer disease, or dementia due to other causes (50062,50597).
• Diabetes. Small clinical studies suggest that oral folic acid does not improve glycemic control. Details: Meta-analyses of small clinical trials in patients with type 2 diabetes show that folic acid does not reduce glycated hemoglobin (HbA1C) when compared with placebo (50528,109197). Another small clinical study in patients with diabetes who are stabilized on metformin and/or a sulfonylurea shows that taking folic acid 5 mg daily for 8 weeks does not affect HbA1C when compared with placebo (104917). The validity of this study is limited by its small size and lack of blinding. Conversely, a meta-analysis of clinical research shows that taking folate modestly reduces fasting blood glucose and insulin levels, as well as measures of insulin resistance, when compared with placebo or no intervention (109197). There was no clear relationship between these changes and the dose or duration of folate. However, the studies included in this analysis evaluated multiple patient populations; the effect of folate in patients with diabetes, specifically, is unclear. Beyond glycemic control, some research has assessed the impact of dietary folate intake on cardiovascular risk in patients with diabetes. An observational study in Chinese adults with type 2 diabetes has found that dietary intake of folate in the highest quartile is associated with 68% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with folate intake in the lowest quartile (110452). Folic acid has also been evaluated in gestational diabetes. A meta-analysis of 20 studies shows that serum and red blood cell (RBC) folate levels are higher in patients with gestational diabetes than without gestational diabetes. Subgroup analysis suggests that patients with gestational diabetes have higher serum and RBC folate levels in the second trimester than in those without gestational diabetes, while RBC folate levels in patients with gestational diabetes were higher in the first trimester than those without gestational diabetes. Overall, higher serum folate levels are associated with a slight increase in the odds of gestational diabetes when compared with lower serum folate levels (112107).
• Diabetic neuropathy. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with diabetic neuropathy shows that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate), for 24 weeks does not improve neural dysfunction based on vibration perception, but does seem to improve total neuropathy symptoms, when compared with placebo. These symptoms, which include both sensation and pain, decreased by 25% with the B vitamin combination, compared with only 15% in those taking placebo (90375).
• Epilepsy. It is unclear if oral folic acid reduces seizure frequency. Details: A meta-analysis of preliminary clinical research shows that taking folic acid does not reduce seizure frequency in patients with epilepsy (50124). However, there is some speculation that folate deficiency might be linked to increased seizure frequency. A preliminary clinical study in folate-deficient children with epilepsy shows that taking folic acid 5 mg daily for 3 months reduces seizure frequency when compared to baseline, but not when compared with a control group that is not deficient in folate (99371).
• Erectile dysfunction (ED). Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in males with mild erectile dysfunction, overweight or obesity, and normal to low androgen levels shows that taking a combination product containing folic acid 400 mcg, alpha-lipoic acid, myo-inositol, and apple (Sinopol Forte, Laborest) improves measures of erectile dysfunction when compared to baseline (111674). The validity of these effects is limited by the small sample size and the lack of a comparator group, and it is unclear if these effects are due to folic acid, other ingredients, or the combination.
• Esophageal cancer. Higher dietary folate intake is associated with a lower risk of esophageal cancer. Details: One meta-analysis of observational research has found that higher levels of dietary folate are associated with a 34% lower risk of esophageal squamous cell carcinoma and a 50% lower risk of esophageal adenocarcinoma when compared with low levels of dietary folate (50208). Another meta-analysis of observational research has found that consuming high amounts of folate is associated with a 36% decrease in the odds of esophageal cancer when compared with lower dietary folate intake (100950).
• Fenofibrate (Tricor)-induced hyperhomocysteinemia. Folic acid seems to attenuate increases in homocysteine in people taking fenofibrate. Details: A small open-label clinical trial in patients taking fenofibrate shows that adding folic acid 10 mg every other day might reduce elevated plasma homocysteine levels by up to 59% when compared with taking fenofibrate alone (9321).
• Gastric cancer. It is unclear if oral folic acid reduces gastric cancer risk. Details: Observational research has found that taking folic acid reduces the risk of gastric cardia adenocarcinoma by 17% and the risk of noncardia gastric cancer by 33%, but does not reduce the risk of gastric cancer overall (50208). Also, a meta-analysis of 13 small clinical studies in patients with gastric precancerous conditions shows that taking folic acid 20-30 mg daily for 3-6 months improves gastric mucosal atrophy and intestinal metaplasia but does not seem to improve symptoms when compared with a control (110448). Whether these findings are associated with a lower risk of gastric cancer is unclear.
• Gout. It is unclear if oral folic acid reduces the risk for gout. Details: An observational study has found that increased dietary folate intake is associated with a lower incidence of gout (50454).
• Head and neck cancer. It is unclear if oral folic acid is beneficial for head and neck cancer prevention. Details: Population research has found that the highest intake of dietary folate is associated with a 50% reduced risk of head and neck cancer when compared with the lowest intake of folate. Each 100 mcg increase per day seems to reduce the risk by about 4% (96151).
• Hearing loss. It is unclear if oral folic acid prevents hearing loss. Details: Low levels of serum folate seem to be a risk factor for sudden sensorineural hearing loss in adults (21283). Observational research in females has found that serum folate levels in the lowest quintile are associated with a 19% increased risk for hearing loss when compared with levels in the second quintile. Also, folate levels in the highest quintile are associated with a 12% lower risk of hearing loss when compared with the second quintile (109807). A clinical study in older adults from the Netherlands shows that taking folic acid 800 mcg daily for 3 years slows the decline of age-related low-threshold hearing loss when compared with placebo (15163). However, at the time of this study, folate enrichment of foods was not allowed in the Netherlands. As a result, baseline folate levels in this study population were about 50% lower than in the US population. The effect of folic acid supplementation in people with higher baseline folate levels is unclear.
• Infertility. It is unclear if oral 5-methyltetrahydrofolate (5-MTHF) in combination with vitamin B6 and vitamin B12 is more beneficial than folic acid alone for increasing pregnancy rate in females undergoing assisted reproductive technology (ART). Details: Retrospective research from Italy suggests that taking 5-MTHF 400 mcg, vitamin B12 5 mcg, and vitamin B6 3 mg daily results in clinical pregnancy and live birth rates of approximately 60% and 49%, respectively, compared with 45% and 35% of those taking folic acid 400 mcg daily. A sub-analysis suggests that beneficial effects on pregnancy rates are limited to individuals aged less than 40 years (109189). The findings from this study are limited by its retrospective design. Also, it is unclear if these findings are generalizable to countries with folate fortification.
• Kidney failure. It is unclear if oral folic acid is beneficial in patients with kidney failure. Details: Because hemodialysis removes folate from the body, there is concern that folate deficiency may cause complications in patients with kidney failure receiving hemodialysis. Observational research in Taiwanese patients with kidney failure undergoing hemodialysis has found that taking folic acid 5 mg daily for an average of 5.8 years is associated with a 31% lower risk of arteriovenous access thrombosis when compared with folic acid 5 mg weekly. However, daily folic acid supplementation was not linked to a lower risk of cardiovascular events, cancer, or mortality when compared with weekly folic acid (110120). Oral folic acid has also been evaluated in combination with other ingredients. A small, low-quality clinical study in adults with kidney failure undergoing regular hemodialysis shows that taking oral folic acid 30 mg daily with thiamine 90 mg daily for 96 weeks reduces overall mortality by 67% and improves cognitive scores by 31% when compared with no intervention (107724). It is unclear if these findings are due to folic acid, thiamine, or the combination.
• Lometrexol toxicity. While oral folic acid might reduce lometrexol toxicity, intravenous folic acid does not seem to help. Details: In a phase I trial, intravenous folic acid 5-25 mg administered 1 hour or 3 hours prior to lometrexol 15-30 mg/m2 every 3 weeks does not seem to reduce cumulative lometrexol toxicity (2161). However, in a phase II study, taking oral folic acid 3 mg/m2 daily in addition to lometrexol 10 mg/m2 weekly seems to attenuate cumulative toxicity and improve its tolerability in cancer patients (104948).
• Low birth weight. It is unclear if oral folic acid supplementation during pregnancy reduces the risk of a low birth weight. Details: Clinical research shows that supplementation with folic acid 200 mcg to 5 mg daily during pregnancy increases mean birth weight when compared with placebo (91307). Furthermore, some population research has found that pre- or peri-conception folic acid supplementation, usually 400 mcg daily, is associated with a reduced risk of a child born small-for-gestational age. However post-conception folic acid supplementation is not associated with reduced risk (91304,103983). An observational study in pregnant Chinese patients found that supplementation with folic acid is associated with a 20% lower odds of low birth weight when compared with no supplementation. This association was observed when folic acid was used both before conception and during pregnancy for at least 24 weeks or during pregnancy only for at least 12 weeks. Increased dietary folate intake was not linked to a lower risk of low-birth-weight infants (110446). However, other observational research has found no association between folic acid supplementation during pregnancy and the risk for small-for-gestational age births (110447).
• Lung cancer. It is unclear if oral folic acid reduces lung cancer risk. Details: There does not appear to be a relationship between deficiency of folate and lung cancer (9454). However, consuming at least 130.4 mcg of folate per 1000 kcal daily seems to reduce the risk of lung cancer by 40% in former smokers when compared to those with lower dietary folate intake (50065).
• Melanoma. It is unclear if oral folic acid reduces melanoma risk. Details: Population research has found that folic acid supplementation of 2-2.5 mg daily in combination with vitamin B6 and vitamin B12 is linked with a 53% reduced risk of melanoma (91312).
• Metabolic syndrome. Although there is interest in using oral folic acid for metabolic syndrome, there is insufficient reliable information about the clinical effects of folic acid for this condition.
• Nitrate tolerance. It is unclear if oral folic acid helps to prevent the development of tolerance to treatment with nitroglycerin. Details: Some clinical evidence suggests that taking folic acid 1 mg daily for 1 week does not prevent the development of nitroglycerin-induced endothelial dysfunction or tolerance in healthy individuals (50442). However, other research suggests that taking folic acid 10 mg daily for 1 week prevents nitric oxide synthase dysfunction caused by continuous nitroglycerin (9316).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral folic acid is beneficial for NAFLD. Details: A cross-sectional analysis suggests that adults with NAFLD have lower levels of serum folate and its major component 5-MTHF when compared with healthy controls. Additionally, adults with NAFLD seem to consume less supplementary and dietary folate when compared with healthy controls. Overall, serum folate levels are negatively associated with the risk of NAFLD, and inadequate folate intake is associated with an increased risk of NAFLD (112104).
• Oral clefts. It is unclear if oral folic acid reduces the risk of oral clefts in infants. Details: Observational research has found that maternal folic acid supplementation is associated with an up to 49% reduced risk of cleft lip with or without cleft palate (50220,104921). Furthermore, a large clinical trial in pregnancies at-risk for oral cleft suggests that taking a higher dose of folic acid 4 mg from pre-conception until the end of the first trimester results in a similar oral cleft recurrence rate of 2.5%, compared with a 2.9% recurrence with a lower dose of folic acid (400 mcg). Both doses demonstrate a lower incidence of oral clefts when compared with historical rates of 6.3% (91322). Although there is speculation that genetic markers of folate status impact the effect of folic acid on orofacial cleft incidence, the current data do not show a relationship (104921).
• Overall mortality. It is unclear if oral folic acid reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of folic acid in the highest quintile is associated with a 14% to 23% lower risk of all-cause mortality and a 41% to 47% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary folic acid intake (110451).
• Pancreatic cancer. It is unclear if oral folic acid reduces pancreatic cancer risk. Details: Consuming greater than 280 mcg daily of dietary folate is associated with a decreased risk of exocrine pancreatic cancer (9327). A meta-analysis of case-control and cohort studies suggests that consuming higher amounts of dietary folate reduces the risk of pancreatic cancer by 51% compared to low levels of dietary folate (50208). However, another meta-analysis of prospective cohort studies suggests that folate/folic acid intake does not significantly affect the overall risk of pancreatic cancer (50499). The contradictory results may be associated with the form of intake or may be related to the gender of the participants. A meta-analysis of clinical research shows that dietary folate, but not folic acid, significantly reduces the risk of pancreatic cancer (50387). Also, one meta-analysis of observational studies has found that high dietary folate decreases the risk of pancreatic cancer in females, but not males (50387).
• Peripheral neuropathy. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows taking a combination of folic acid 400 mcg, vitamin B12 3 mcg, and uridine monophosphate 50 mg daily (Keltican) for 60 days reduces pain associated with peripheral neuropathy. Use of this product reduces pain intensity by approximately 44%, with loss of burning pain in approximately 50% of patients, strong tingling or pricking in approximately 57% of patients, strong pain attacks in 92% of patients, and numbness in 90% of patients when compared with baseline. Radiating pain and the use of concomitant medications are also reduced (90384). The validity of this finding is limited by the lack of a comparator group. Furthermore, it is unclear if the benefits are due to folic acid, other ingredients, or the combination.
• Pharyngeal cancer. It is unclear if oral folic acid reduces pharyngeal cancer risk. Details: Population research has found that intake of folic acid and folate from natural, fortified, and supplemented sources, may protect against oropharyngeal cancer. Intake of at least 258-816 mcg total folate/folic acid reduces the odds by 35% when compared with intakes of less than 344 mcg. Furthermore, folate/folic acid may be more beneficial for oral cancer versus pharyngeal cancer and in heavy alcohol users versus non users or light users (91302).
• Polycystic ovary syndrome (PCOS). It is unclear if oral folic acid is beneficial for PCOS. Details: One clinical study in overweight or obese patients with PCOS shows that taking folate 1 mg or 5 mg daily for 8 weeks modestly reduces levels of homocysteine, as well as insulin resistance, when compared with placebo. However, only the 5 mg dose modestly reduces insulin, total cholesterol, and low-density lipoprotein (LDL) cholesterol levels. Neither dose appears to affect fasting plasma glucose, high-density lipoprotein (HDL) cholesterol, or triglyceride levels when compared with placebo (109200). Other clinical research in patients with PCOS taking metformin shows that taking folate 400 mcg daily for 6 months does not affect glycemic parameters, plasma lipid levels, or hormone levels when compared with placebo (109194). The reasons for discrepancies between studies are unclear but may relate to patient characteristics. One study included only overweight or obese individuals with at least two of the three PCOS criteria, whereas the other study limited enrollment to patients in any weight category but with all three PCOS criteria (109194,109200).
• Pregnancy-induced hypertension. It is unclear if oral folic acid reduces the risk of hypertension during pregnancy. Details: Population research has found that taking folic acid during pregnancy is not associated with a reduced risk of gestational hypertension (91308,99370,99372).
• Restless legs syndrome (RLS). Although there is interest in using oral folic acid for RLS, there is insufficient reliable information about the clinical effects of folic acid for this condition.
• Schizophrenia. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination of folic acid 2 mg and vitamin B12 400 mcg daily for 16 weeks improves negative symptoms when compared with placebo in patients with schizophrenia who have persistent symptoms and a specific genetic variant of the folate transporter gene FOLHI. This variant normally results in reduced folate absorption. However, in patients without this genetic variant, folate is not beneficial with respect to negative symptom improvement (90387).
• Sickle cell disease. Oral folic acid has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B12 4.2-6 mcg, folic acid 700 mcg, and vitamin B6 4.2-6 mg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
• Suicidal ideation. It is unclear if oral folic acid reduces the risk of suicidal ideation or suicide attempts. Details: One observational study has evaluated the association between folic acid supplementation and suicidal events in patients with various underlying conditions, including 12% with depression, 15% with anxiety, and 46% with pain. This within-person cohort study found that filling a prescription for folic acid 0.4-5 mg daily, either alone or as part of a multivitamin, is associated with a 44% reduced rate of suicidal events during the months after the prescription when compared with the months without the prescription. For the 48% of patients who received folic acid 1 mg daily, each additional month of taking the prescription was associated with a 5% decrease in suicidal events (109201). Prospective clinical research is needed to confirm any benefits of folic acid and to determine whether baseline folate deficiency plays a role in these outcomes. More evidence is needed to rate folic acid for these uses.

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POSSIBLY EFFECTIVE

• Angina. Oral L-arginine seems to improve symptoms and exercise tolerance in patients with angina. Details: Clinical research shows that taking L-arginine orally seems to decrease symptoms and improve exercise tolerance and quality of life in patients with mild to severe angina (3593,7815,7816,31866,31923). Some patients with severe angina who have frequent attacks at rest despite treatment with standard antianginal agents might also benefit from L-arginine (3593). However, L-arginine does not seem to improve objective measures of blood vessel dilation or increase circulating concentrations of nitric oxide (7817,99262). Also, when used in combination with ten 200 mcg injections of vascular endothelial growth factor (VEGF)-165 plasmid DNA, L-arginine 6 grams daily orally for 3 months does not improve angina severity in patients with coronary artery disease who underwent surgical angiogenesis compared to patients who did not receive this combination (32001). In addition, intravenous infusion of arginine 10% solution does not improve exercise capacity in patients with stable angina when compared with placebo (31843,32293).
• Erectile dysfunction (ED). Oral L-arginine might improve symptoms of ED. When taken with phosphodiesterase type 5 (PDE5) inhibitors, L-arginine seems to provide a small additional benefit. Details: Taking L-arginine orally in high doses, 5 grams daily, improves subjective assessment of sexual function in males with organic ED when compared with placebo (222,102586). Additionally, a meta-analysis of 4 small clinical studies in patients with ED, including those with diabetes and/or cardiovascular disease risk factors, shows that although PDE5 inhibitors improve sexual function better than L-arginine, the combination of PDE5 inhibitors and L-arginine may be more effective than either treatment alone (105065). In most clinical trials, doses of L-arginine 2.5-5 mg daily for 6-12 weeks were used alone or in addition to PDE5 inhibitors such as sildenafil 50 mg or tadalafil 5-10 mg daily (102586,102587,102592,104222). Higher doses have also been investigated. One clinical trial shows that taking L-arginine (Bioarginina, Farmaceutici Damor S.p.A., Napoli, Italy), 2 grams three times daily for 3 months improves sexual function compared with placebo (110387). However, taking lower doses, 1.5 grams daily, might not be effective in patients with mixed-type ED (2038). L-arginine has also been examined in combination with other ingredients. A meta-analysis of 2 small clinical studies in males with mild-to-moderate ED shows that taking L- arginine, up to 3 grams daily, in combination with maritime pine for 1-6 months improves a subjective assessment of sexual function when compared with control (112715). Some preliminary clinical evidence suggests that taking L-arginine orally in low doses, 1.7 grams daily in combination with maritime pine bark extract (Pycnogenol) or taking 0.69 grams daily along with maritime pine bark extract and aspartic acid (Edicare, Kobayashi Pharmaceutical Co. Ltd.) modestly improves symptoms of ED (10416,50924). Another preliminary clinical trial has investigated the effects of a combination of L-arginine 2.5 grams daily for 6 months and tadalafil 5 mg daily for 3 months, both starting with the initiation of weekly extracorporeal shock wave (ESW) therapy. When compared with ESW alone, this combination modestly improves sexual function for up to 12 months (110388). The effect of L-arginine alone is not clear from these studies.
• Hypertension. Oral L-arginine can modestly reduce systolic and diastolic blood pressure. Details: Oral L-arginine seems to have additive vasodilating effects when used with angiotensin converting enzyme (ACE) inhibitors or nitrate vasodilators such as isosorbide mononitrate (7822,20192,31916). A meta-analysis of clinical research in a variety of populations shows that taking L-arginine reduces systolic and diastolic blood pressure (SBP; DPB) by an average of 6.40 mmHg and 2.64 mmHg, respectively. Sub-analyses show that these reductions occur in both normotensive and hypertensive individuals. Beneficial effects were limited to adults with a body mass index (BMI) of 18.5 to 19.9 kg/m² (110384). The effect of L-arginine on blood pressure levels in adults exposed to traffic-related air pollution (TRAP) has also been investigated. Clinical research in adults with hypertension shows that taking L-arginine 3 grams three times daily for 2 weeks modestly reduces SBP and DBP elevations following a 2-hour exposure to TRAP during an outdoor walk compared with taking placebo (110383). Doses have included 4-24 grams daily, with the best evidence of benefit for doses of less than 9 grams daily, for 2-24 weeks (7818,10636,31871,31923,32167,32201,110383,110384).
• Necrotizing enterocolitis (NEC). Oral L-arginine may help prevent NEC in premature infants. Details: In a meta-analysis of 3 clinical trials, L-arginine 260 mg/kg orally in a single dose or two divided doses daily reduces the absolute risk of NEC in premature infants by about 62% when compared with placebo. To prevent one case of NEC, 6 infants would need to be treated with L-arginine (8474,91194,96803).
• Peripheral arterial disease (PAD). Short-term use of intravenous or oral L-arginine may improve symptoms of PAD, but long-term use does not seem to be beneficial. Details: Clinical research shows that using L-arginine intravenously or orally for up to 8 weeks increases flow-mediated dilation and improves symptoms of intermittent claudication associated with PAD (3465,31857,31905). However, long-term administration of L-arginine orally for up to 6 months does not improve walking speed, walking distance, or absolute claudication distance in patients with PAD and intermittent claudication (31957,31985).
• Pre-eclampsia. Intravenous L-arginine may have beneficial effects in pre-eclampsia. However, it is unclear if oral L-arginine is effective. Details: One small clinical study shows that intravenous L-arginine 30 grams as a one-time dose decreases systolic blood pressure (SBP) by 5 mmHg and diastolic blood pressure by 11 mmHg when compared to baseline in pregnant patients with hypertension or pre-eclampsia (31847), while intravenous L-arginine 20 grams daily for 5 days decreases SBP and DBP by about 2% when compared with placebo (31978). Another small clinical study shows that oral use of L-arginine 3 grams daily for 3 weeks reduces SBP and DBP by around 7 and 5 mmHg, respectively, when compared with placebo (31938); however, taking L-arginine 12 grams daily by mouth for 5 days does not seem to improve blood pressure in these patients (11828). Another preliminary clinical trial allowing for both oral and intravenous dosing shows that taking L-arginine 3.5 grams by mouth every 6 hours or 10 grams via intravenous infusion every 8 hours shortly before or immediately after delivery and continuing until postpartum day 3 does not improve blood pressure when compared with placebo (31959). The reasons for the disparate findings are unclear, but the small study sizes, as well as variations in the dose, duration, and timing of therapy before and/or after delivery, may explain some of the differences. Oral L-arginine has also been evaluated for the prevention of pre-eclampsia. One clinical study in patients at high risk for pre-eclampsia shows that taking L-arginine 3 grams daily starting the 20th week of gestation reduces the risk of pre-eclampsia by about 74% when compared with placebo (96811). Based on these results, one case of pre-eclampsia is prevented for every 6 high-risk pregnant patients treated with L-arginine 3 grams daily. Another clinical study also shows that taking two bars of a specific medical food (Heart Bars, Nellson Nutraceutical) containing L-arginine 6.6 grams and antioxidant vitamins daily starting at 14-32 weeks gestation and continuing until delivery reduces the risk of pre-eclampsia by 44% when compared with a bar containing antioxidant vitamins alone in patients at high risk of pre-eclampsia (91197). Based on these results, one case of pre-eclampsia is prevented for every 11 high risk patients treated with this L-arginine-containing medical food.
• Pregnancy-induced hypertension. Intravenous L-arginine may have beneficial effects in pregnancy-induced hypertension. Details: Some clinical research in patients with pregnancy-induced hypertension shows that intravenous infusion of L-arginine 20 grams daily for up to 5 days decreases systolic blood pressure by 2% to 3% and diastolic blood pressure by about 3% when compared with placebo (31933,31961,31978). Clinical research in patients with pre-existing hypertension has also been conducted. One clinical trial shows that taking L-arginine 4 grams by mouth daily for 10-12 weeks does not seem to reduce blood pressure in those with pre-existing hypertension or mild gestational hypertension. However, these results are confounded by the fact that more patients taking placebo needed to be placed on antihypertensive therapy during the study. L-arginine reduced the risk of being placed on antihypertensive drug therapy during the pregnancy by 47% when compared with placebo (32191). Based on this study, for every 5 patients with pregnancy-induced hypertension treated with L-arginine over placebo, antihypertensive drug therapy is avoided in one additional patient. L-arginine has also been investigated in combination with other ingredients in patients with pre-existing hypertension. Preliminary clinical research in patients with pre-existing hypertension and a previous history of pre-eclampsia, stillbirth, intrauterine growth restriction (IUGR), or other placenta vascular disorder shows that taking L-arginine and other ingredients starting at 14 weeks gestation prevents an increase in blood pressure and reduces the percentage of patients requiring new antihypertensive medication by about 73% compared with 24.5% of those not taking this combination. In this study, L-arginine 3 grams daily was taken with magnesium 350 mg and salicylate 100 mg. Therefore, the effect of L-arginine alone is unclear. All patients in the study were taking low dose aspirin 100 mg daily (110382).

POSSIBLY INEFFECTIVE

• Chronic kidney disease (CKD). Oral or intravenous L-arginine does not seem to improve CKD. Details: Most preliminary clinical research shows that taking L-arginine, either orally for up to 6 months or intravenously short-term, does not improve kidney function, glomerular filtration rate, or renal plasma flow in patients with CKD, although proteinuria may be reduced in some patients (31844,31904,32235,32303).
• Hypercholesterolemia. Oral L-arginine does not seem to reduce cholesterol levels. Details: Preliminary clinical research in patients with hypercholesterolemia shows that taking L-arginine 21 grams daily for 4 weeks does not reduce plasma lipids (1363). Furthermore, meta-analyses of clinical research show that taking L-arginine for up to about 6 months does not reduce total or low-density lipoprotein (LDL) cholesterol levels in populations of healthy individuals or those with cardiovascular disease risk factors. However, there was a very small effect on fasting triglyceride levels (102590,102591).
• Myocardial infarction (MI). Oral L-arginine does not seem to improve outcomes after MI. Details: Patients who have had an ST-segment MI who take L-arginine within 24 hours to 21 days, titrated up to a dose of 3 grams three times a day for up to 6 months, do not seem to have reduced vascular stiffness or increased ejection fraction (13221,32137). Also, there is some concern that long-term use of L-arginine might actually worsen outcomes and increase mortality in these patients (13221). Population studies also suggest that intake of L-arginine does not reduce the risk of experiencing an acute coronary event such as MI or coronary heart disease-related mortality (3332,6896,7821,10637).
• Tuberculosis. Oral L-arginine does not seem to improve symptoms or the clearance of tuberculosis infection. Details: Clinical research shows that taking L-arginine (ArgimaxH) 6 grams daily orally for 8 weeks, with or without vitamin D, does not improve symptoms of tuberculosis or the clearance of tuberculosis infection when used with standard treatment (91196).
• Wound healing. Oral L-arginine does not seem to improve wound healing. Details: Clinical research shows that taking L-arginine (as arginine aspartate) 17 grams orally in three divided doses daily for 2 weeks does not improve epithelialization in healthy, elderly patients with catheter wounds, although it may improve collagen deposition (32247). Also, taking L-arginine (as L-arginine hydrochloride) 26 grams daily for 5 days perioperatively does not improve angiogenesis, re-epithelialization, or neutrophil count in patients undergoing skin graft donation when compared with placebo (20692). In addition, taking a wound-specific oral nutrition supplement containing L-arginine 4.5 grams, zinc, and vitamin C twice daily for 4 weeks, along with standard wound care for 8 weeks, is no more effective for wound healing than a standard oral nutrition supplement along with standard wound care (90198). L-arginine has also been studied in combination with other ingredients. Taking L-arginine enterally or orally, before or after surgery, in combination with ribonucleic acid (RNA) and either eicosapentaenoic acid (EPA) or fish oil, seems to improve wound healing when compared with a control group (5531,32174). Another observational study conducted in Italy in newborns shows that applying a specific topical powder containing L-arginine, arnica extract, zinc oxide, and other ingredients (Cicaben, Orsana Italia S.r.l.) to the newborn's umbilical cord stump 3 to 4 times daily until stump detachment reduces the rates of mild complications 48 hours after discharge such as a wet cord stump but does not change the time to cord stump detachment or the rates of purulent secretions or umbilical granulomas when compared with standard dry care. However, no differences were noted between the groups one week after discharge (113662). The validity of these results is limited by the observational nature of the study and the ability of the parents to select a treatment group. It is unclear if the effects in these studies are due to L-arginine, other ingredients, or the combination.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acute respiratory distress syndrome (ARDS). Small clinical studies suggest that oral L-arginine may prevent ARDS. Details: A meta-analysis of three small studies shows that taking L-arginine 3 grams daily, starting in the second or third trimester usually until delivery, reduces the risk of ARDS in the infant by about 54% when compared to control, including placebo or no treatment (110379).
• Altitude sickness. It is unclear if oral L-arginine is beneficial in patients with altitude sickness. Details: Preliminary clinical research shows that taking L-arginine 4 grams orally three times daily for 2 days while ascending to a high altitude and for 24 hours while at high altitude does not reduce altitude sickness when compared with placebo (31955).
• Anthracycline cardiotoxicity. Although there is interest in using oral L-arginine for anthracycline cardiotoxicity, there is insufficient reliable information about the clinical effects of L-arginine for this purpose.
• Anemia of chronic disease. It is unclear if oral L-arginine is beneficial for anemia in patients with chronic kidney disease. Details: One very small clinical study in elderly adults with chronic kidney disease and anemia shows that taking L-arginine orally 1.3 grams daily might increase hemoglobin and erythropoietin levels in some patients when compared to baseline (31988). The validity of these findings is limited by the small study size and the lack of a comparator group.
• Asthma. It is unclear if oral L-arginine is beneficial in patients with asthma. Details: Preliminary clinical research in adults with severe asthma shows that taking L-arginine 0.05 gram/kg ideal body weight twice daily does not reduce asthma exacerbations when compared with placebo (104223). This study may have been inadequately powered to detect a difference in exacerbation rates between groups. While other studies have shown adverse airway effects in patients with asthma (121,31849), this study demonstrated no change in exacerbations and reported no adverse airway effects.
• Athletic performance. Small clinical studies suggest that oral L-arginine may improve measures of athletic performance. Details: A meta-analysis of 5 small clinical trials shows that taking L-arginine seems to modestly improve measures of cardiorespiratory fitness, as measured by a 0.07 L/minute increase in maximal oxygen uptake, when compared with control (105064). L-arginine has also been examined for its effects on athletic performance. Most research suggests that taking L-arginine does not improve athletic performance. However, clinical trials are small and may not be adequately powered to detect a difference in these outcomes Taking L-arginine as a single dose of 5 or 6 grams or as 5-10 grams daily for 2-4 weeks does not improve grip strength, strength during resistance exercise, power output during cycling, or muscle function during recovery from intense resistance exercise in healthy adults (91190,97393,99265,110381,110389). Also, taking L-arginine 5 grams daily for 4 weeks (Bioarginina Farmaceutici Damor) or 8 grams daily for 8 days does not increase swim speed (110381,110386). In contrast, some research suggests that drinking a single beverage containing the same dose of L-arginine 6 grams increases the time to exhaustion during high-intensity exercise when compared with placebo (32180). Also, a meta-analysis of small clinical trials shows that supplementation with L-arginine has a large beneficial effect on aerobic performance and a small beneficial effect on anaerobic performance. However, publication bias was evident in the aerobic performance data, limiting these conclusions. Doses found to be beneficial in this analysis included an acute dose of L-arginine 0.15 gram/kg 60-90 minutes before performance or chronic dosing of 1.5 grams to 2 grams daily for 4-7 weeks for aerobic performance. The chronic dose of L-arginine most likely to be beneficial for anaerobic performance is unclear from this analysis due to inclusion of studies using arginine alpha-ketoglutarate (110395). With the exception of a few studies which include a very small number of healthy females (99265,110395,110386), research on the use of L-arginine for athletic performance has focused almost exclusively on healthy males. Also, studies are heterogeneous with respect to sport and endpoints. Therefore, whether results can be applied to females or specific athletes is unclear. L-arginine has also been evaluated in overweight males. One small clinical study shows that taking a single dose of L-arginine 6 grams 90 minutes prior to high-intensity interval training seems to improve exercise tolerance by improving ventilation, heart rate, and oxygen uptake when compared with placebo (105060). L-arginine has also been evaluated in combination with other ingredients. Research in male soccer players shows that taking L-arginine 1.2 grams and L-citrulline 1.2 grams daily for 7 days increases total power output over a 10-minute cycling test and improves subjective perceptions of exertion when compared with placebo (100956). Another study shows that taking L-arginine 1.5 or 3 grams daily, in combination with grape seed extract, increases physical working capacity at fatigue threshold when compared with pretreatment in untrained, college-aged males (32164).
• Beta-thalassemia. It is unclear if oral L-arginine is beneficial in children with beta-thalassemia. Details:Preliminary clinical research in children aged 6-18 years treated conventionally for pulmonary hypertension related to beta-thalassemia shows that taking L-arginine 0.1 mg/kg daily for 60 days reduces Doppler echocardiography pulmonary arterial pressure by 35% compared with baseline. This measurement was increased by up to 15% in children given conventional treatments only; however, a statistical comparison between these treatment groups was lacking (110391).
• Breast cancer. It is unclear if oral L-arginine is beneficial in patients with breast cancer. Details: Preliminary clinical research shows that taking L-arginine 30 grams daily for 3 days prior to chemotherapy does not improve the clinical response rate in breast cancer patients when compared with placebo (32282).
• Cognitive impairment. It is unclear if oral L-arginine is beneficial in patients with cognitive impairment. Details: A small clinical trial in frail adults aged 65 years of age and up with hypertension shows that taking L-arginine (Bioarginina) 1.66 grams twice daily for 4 weeks modestly improves cognitive function when compared to placebo (110385).
• Congestive heart failure (CHF). It is unclear if oral L-arginine is beneficial in patients with CHF. Details: One small clinical study in patients with CHF stage 2-3 shows that taking L-arginine 15 grams daily for 5 days, in combination with conventional treatment, seems to improve glomerular filtration rate (GFR), creatinine clearance, and sodium and water elimination after saline loading, indicating an improvement in kidney function (3596).
• Coronavirus disease 2019 (COVID-19). It is unclear if oral L-arginine is beneficial in patients with severe COVID-19 infection. Details: A small clinical trial in patients with severe COVID-19 shows that receiving oral L-arginine (Argin, Nutrigrow, India) 3 grams daily for a maximum of 10 days while on oxygen support does not affect the percentage of patients weaned off oxygen support after 10 days, the length of time requiring oxygen support, the duration of hospitalization, or the incidence of adverse thrombotic events, compared with placebo (110392). This study may not have been adequately powered to detect differences between groups. An interim analysis of a small clinical trial in patients hospitalized with severe COVID-19 shows that adding oral L-arginine (Bioarginina, Farmaceutici Damor) 1.66 grams twice daily to standard therapy throughout hospitalization increases the rate of respiratory support reduction by 60% after 10 days of therapy, but not after 20 days of therapy, when compared with placebo. L-arginine also significantly reduced the length of hospital stay. The median hospital stay was 25 days and 46 days, respectively, for L-arginine and placebo (106500). L-arginine has also been investigated in combination with other ingredients for post-acute COVID symptoms. Preliminary clinical research in adults with persistent fatigue following a COVID infection shows that taking L-arginine 1.66 grams plus vitamin C 500 mg (Bioarginina C, Farmaceutici Damor) twice daily for 28 days increases the distance walked in 6 minutes by 30 meters and reduces the percentage of patients with fatigue by about 89%, when compared with placebo. Grip strength was also increased (110390).
• Coronary artery bypass graft (CABG) surgery. It is unclear if oral L-arginine is beneficial for preventing complications after CABG surgery. Details: Preliminary clinical research shows that venous infusion of L-arginine hydrochloride 30 grams as a 10% solution over 15 minutes helps maintain mean arterial pressure, coronary vascular resistance, and graft blood flow when compared with a placebo infusion in patients that have undergone CABG (31840). Administering L-arginine 7.5 grams in 500 mL of cardioplegic solution also seems to reduce wedge pressure and intensive care unit stay in patients undergoing CABG; however, it does not reduce hospital stay duration or postoperative complications when compared with cardioplegic solution alone (31958,31886).
• Critical illness (trauma). Oral L-arginine has only been evaluated in combination with other ingredients; its effects when used alone are unclear. Details: A meta-analysis of clinical research shows that taking L-arginine orally with glutamine, nucleotides, and omega-3 fatty acids reduces the recovery time, the need for ventilation, and infection rates in critically ill patients, but does not reduce the risk of mortality (31853).
• Cyclosporine-induced nephrotoxicity. Although there is interest in using oral L-arginine for cyclosporine-induced nephrotoxicity, there is insufficient reliable information about the clinical effects of L-arginine for this purpose.
• Cystic fibrosis. It is unclear if oral L-arginine is beneficial in patients with cystic fibrosis. Details: Preliminary clinical research in teens and adults with cystic fibrosis shows that twice daily inhalation with L-arginine 500 mg for 2 weeks does not improve lung function when compared with inhaling 2.6% hypertonic saline twice daily (96807).
• Dental caries. Small clinical studies suggest that using a dentifrice containing L-arginine might prevent dental caries. Details: A meta-analysis of small studies shows that use of a dentifrice containing L-arginine 1.5% w/w in combination with calcium base (Dical or calcium carbonate) and fluoride 1450 ppm 2-3 times daily for up to 2 years reduces the risk of developing dental caries by a small to moderate amount when compared with a dentifrice containing only fluoride in children and adults (96806). Also, preliminary clinical research shows that using a confection containing an L-arginine complex (CaviStat) for one year reduces the number of dental caries in molars of children when compared with a sugarless mint control (32011). L-arginine has also been investigated as a prebiotic in combination with probiotics. In 5- to 9-year-old children with low caries risk, clinical research shows that taking one lozenge daily for 10-12 months containing arginine 20 mg along with Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus, modestly reduces caries severity, but does not reduce caries progression, active caries lesions, plaque, or gingivitis, when compared with placebo (113241,113242).
• Dental hypersensitivity. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that using a toothpaste containing L-arginine, calcium, and fluoride twice daily reduces dentin hypersensitivity when compared with pretreatment or control (32130,32131,32132,32177). Another moderate-sized clinical study in adults shows that applying a topical combination of L-arginine 10% and ibuprofen to tooth enamel surfaces for 10 minutes prior to in-office tooth bleaching reduces the risk and intensity of tooth sensitivity when compared with placebo (115354). It is unclear whether the effects are due to L-arginine, other ingredients, or the combination.
• Diabetes. Small, low-quality studies suggest that oral L-arginine does not improve glycemic control in people with type 2 diabetes. Details: A meta-analysis of small, low-quality studies shows that taking L-arginine 2-20 grams daily for up to 77 weeks decreases fasting blood glucose and serum insulin levels in adults without diabetes. However, no improvements occurred in adults WITH type 2 diabetes. This may be explained by previous studies which suggest L-arginine affects glucose control only in the early steps of beta-cell dysfunction. L-arginine did not improve insulin resistance or glycated hemoglobin (HbA1c) in patients with or without diabetes (104225). Also, a prospective observational study in patients with type 1 or type 2 diabetes has found that taking a specific product (Flebotrofine, AMNOL Chimica Biologica) containing L-arginine for 3 months is not associated with improvements in HbA1c, cholesterol, or triglyceride levels when compared with baseline. Other ingredients in this product included diosmin, troxerutin, hesperidin, black currant extract, and gotu kola extract (108151). The validity of these findings is limited by the lack of a comparator group.
• Diabetic foot ulcers. It is unclear if oral or subcutaneous L-arginine is beneficial in patients with diabetic foot ulcers. Details: A very small clinical study shows that administering L-arginine subcutaneously at the site of diabetic foot ulcers does not decrease healing time or rate of amputation when combined with conventional therapies (14914). Also, taking a specific drink containing L-arginine 7 grams, L-glutamine 7 grams, and calcium hydroxymethylbutyrate (HMB) 1.5 grams (Juven/Abound, Abbott Nutrition) orally twice daily for 16 weeks does not improve diabetic foot ulcer healing when compared with a control drink in non-ischemic patients or those with normal albumin levels. However, in specific populations with low albumin and/or poor limb perfusion, up to 74% more patients had total wound healing when compared with the control drink (96637).
• Diabetic neuropathy. It is unclear if oral L-arginine is beneficial in patients with diabetic neuropathy. Details: Preliminary clinical research shows that taking L-arginine 3 grams daily for 3 months does not improve circulation, disability, or nerve function in patients with diabetic neuropathy when compared with placebo (32145).
• Head and neck cancer. It is unclear if oral L-arginine is beneficial in patients with head and neck cancer. Details: Small clinical studies suggest that enteral nutrition supplemented with L-arginine does not seem to have any beneficial effects on markers of immune function such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), length of postoperative hospital stay, or fistula rates; however, it seems to reduce wounds and general infections after surgery in patients with head and neck cancer when compared with control (10160,32008).
• Heart failure. It is unclear if oral L-arginine is beneficial in patients with heart failure. Details: Preliminary clinical research in adults with heart failure shows that taking L-arginine 3.0-12.6 grams orally daily for 6-12 weeks does not consistently improve exercise tolerance or peripheral vascular resistance (3595,6028,32138). However, some research shows that taking L-arginine 1000 mg three times daily for 10 weeks modestly improves measures of cardiac function compared with placebo (110380). Although some research disagrees (32138), most research shows that taking L-arginine modestly improves quality of life (3595,110380).
• Heart transplant complications. It is unclear if oral L-arginine is beneficial in patients that have received a heart transplant. Details: Preliminary clinical research shows that taking L-arginine 6 grams orally twice daily for 6 weeks increases walking distance and oxygen uptake and delays the ventilatory threshold in heart transplant patients when compared with baseline (32150).
• HIV/AIDS-related wasting. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One clinical study in patients with HIV/AIDS shows that taking L-arginine orally, in combination with hydroxymethylbutyrate (HMB) and glutamine for 8 weeks, increases body weight, particularly lean body mass, and positively affects immune status when compared with placebo (1909). However, other clinical research in HIV-positive patients shows that taking L-arginine 7.4 grams daily orally, in combination with omega-3 fatty acids and a balanced oral nutritional supplement for 6 months, does not improve body weight or fat mass, total energy intake, or immune status when compared to taking the nutritional supplement alone (113).
• Impaired glucose tolerance (prediabetes). It is unclear if oral L-arginine can prevent the development of type 2 diabetes in adults with prediabetes. Details: Clinical research shows that taking L-arginine (Bioarginine, Farmaceutici Damor) 3.2 grams orally twice daily for 18 months does not reduce the incidence of diabetes in patients with impaired glucose tolerance (prediabetes). However, when assessed one year after treatment discontinuation, patients who took L-arginine had a 58% lower risk of developing diabetes when compared with placebo (91195).
• Infertility. It is unclear if oral L-arginine improves outcomes in people undergoing an assisted reproductive technology (ART) program. Details: Some preliminary clinical research shows that taking L-arginine 16 grams daily decreases the cancellation rate of in vitro fertilization (IVF) and increases the number of oocytes collected in females undergoing an ART program when compared with control. However, taking L-arginine does not seem to improve the number of viable pregnancies (31842). A small clinical study of females undergoing an ART program shows that taking a combination product containing L-arginine 1 gram with folate 200 mcg or L-arginine 2 grams, folate 400 mcg, and vitamin E 10 mg daily for 12 weeks does not affect the hCG-positive rate or clinical pregnancy rate when compared with placebo. A subgroup analysis suggests that taking these combination products might improve HCG-positive and clinical pregnancy rates in females who are undergoing ART due to male infertility (104224). However, this small study was not adequately powered to detect a difference in these outcomes, limiting the validity of these findings.
• Interstitial cystitis. Small clinical studies suggest that oral L-arginine may improve pain in interstitial cystitis. Details: Taking L-arginine orally seems to reduce some symptoms, especially pain, that are associated with interstitial cystitis (107,114,3460,31855,32267). Research shows that patients with interstitial cystitis having a bladder capacity greater than 800 mL and/or a history of recurrent genitourinary infections might respond more favorably to L-arginine than patients with bladder capacity less than 800 mL and/or no history of recurrent genitourinary infections. Three months of treatment may be necessary before significant symptom improvement occurs (3460). However, L-arginine does not seem to reduce the need to urinate at night or improve urgency or frequency of urination (3460,31855).
• Intrauterine growth restriction (IUGR). Small clinical studies suggest that oral or intravenous L-arginine may increase birthweight in IUGR. Details: A meta-analysis of mainly small studies shows that L-arginine given orally or intravenously in the third trimester for a time period of 7 days or until delivery increases the birthweight by up to 650 grams in patients with an IUGR pregnancy. Furthermore, there is evidence from a small number of these studies that L-arginine supplementation decreases the risk of neonatal respiratory distress syndrome and fetal intracranial hemorrhage (96804). A more recent meta-analysis of small studies also shows that taking L-arginine 3 grams daily, starting in the second or third trimester usually until delivery, reduces the risk of an IUGR infant by about 32% when compared to control, including placebo or no treatment (110379). Doses used in clinical research have usually been 3 grams daily orally, although some studies have used up to 20 grams intravenously (31930,31937,96804,110379). However, supplementation with L-arginine does not seem to increase birthweight or reduce neonatal mortality or morbidity when compared with placebo in patients with severe IUGR (32083).
• Kidney transplant. Small clinical studies suggest that oral L-arginine may not improve kidney function in patients after kidney transplantation. Details: Although preliminary clinical research showed some benefit, evidence from other clinical research shows that infusion with L-arginine does not increase renal plasma flow or glomerular filtration rate in kidney transplant patients treated with cyclosporine, including those experiencing transplant dysfunction (112,31876,32229). Other evidence suggests that intravenous L-arginine improves kidney function only in transplant patients receiving organs with a short cold ischemia time or those receiving kidneys from young donors (31887).
• Male infertility. It is unclear if oral L-arginine is beneficial in males with infertility. Details: Preliminary clinical research shows that taking L-arginine 4 grams daily for 12 weeks does not improve semen quality in males with oligospermia when compared with placebo (32209). However, one small clinical study shows that a specific formulation of L-arginine aspartate and maritime pine bark extract (Prelox), taken for 6 months, improves sperm quality in males with idiopathic male infertility when compared to baseline (32061). The validity of this finding is limited by the lack of a comparator group. Additionally, it is unclear if this effect is due to L-arginine, maritime pine bark, or the combination.
• Mitochondrial myopathies. Small clinical studies suggest that intravenous L-arginine may modestly improve symptoms in patients with MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes syndrome). Details: Preliminary clinical research shows that infusions of L-arginine, 0.5 grams/kg administered within one hour of stroke-like symptoms, improves headaches, nausea, vomiting, transient blindness, and the appearance of bright spots when compared to pretreatment in patients with MELAS (31943,99263). Also, taking oral L-arginine 4-24 grams daily for 18 months seems to reduce the frequency and severity of stroke-like symptoms associated with MELAS when compared to baseline (31943). However, other preliminary clinical research shows that taking oral L-arginine 0.3-0.5 grams/kg daily in three divided doses for 2 years does not reduce the severity of MELAS symptoms, including migraine and stroke-like episodes. If a stroke-like episode did occur, administration of intravenous L-arginine 0.5 grams/kg improved headache, nausea, vomiting, and visual disturbance (99263). The validity of this research is limited by the small study sizes and the absence of comparator groups.
• Migraine headache. Although there is interest in using oral L-arginine for migraine, there is insufficient reliable information about the clinical effects of L-arginine for this condition.
• Muscular dystrophy. There is limited evidence on the oral use of L-arginine in patients with Duchenne muscular dystrophy. Details: A very small study in five children with Duchenne muscular dystrophy, shows that drinking a beverage containing L-arginine hydrochloride (L-Arginine Hydrochloride, Selectchemie) 2.5 grams three times daily, in addition to metformin 250 mg twice daily, for 16 weeks improves motor function by 4% and increases distance walked in two minutes by 9.6 meters when compared to baseline (96805). The validity of these findings is limited by the very small study size and lack of a comparator group.
• Nitrate tolerance. It is unclear if oral L-arginine is beneficial for nitrate tolerance. Details: A very small crossover study in adults with stable angina shows that taking L-arginine orally 700 mg four times daily for up to 10 days seems to prevent tolerance to transdermal nitrate when compared with placebo (8475).
• Obesity. Small clinical studies suggest that oral L-arginine may be beneficial for weight loss. Details: A meta-analysis of mainly small clinical trials shows that taking L-arginine daily for at least 8 weeks modestly reduces body weight, body mass index (BMI), and waist circumference when compared with placebo. However, when taking L-arginine for less than 8 weeks, BMI and body weight were not affected. The optimal dose of L-arginine was 2-6 grams (110398). An additional small clinical study suggests that taking a specific arginine supplement (NOW Foods) 3 grams by mouth three times daily for 12 weeks, in addition to receiving dietary counseling, reduces waist circumference by 4-6 cm and reduces body weight by 1.8-2.9 kg when compared to baseline in obese females 18-40 years of age (91193). The validity of these findings is limited by the lack of a comparator group.
• Oral mucositis. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study shows that taking a specific combination of L-arginine 7 grams, L-glutamine 7 grams, and hydroxymethylbutyrate (HMB) 1.2 grams (Abound; Abbott) in water twice daily during chemoradiotherapy treatment for head and neck cancer does not reduce the incidence of severe oral mucositis when compared with a historical control (99243). The validity of this finding is limited by the lack of a placebo control. Additionally, a small open-label study in patients undergoing chemoradiation for head and neck cancer shows that taking a specific combination product (Abound, Abbot) containing L-arginine, glutamine, and HMB twice daily throughout chemoradiation treatments decreases the incidence of grade 3 or higher oral mucositis and ameliorates body weight loss when compared with no intervention (113726). However, the incidence of grade 2 or higher oral mucositis was not reduced. It is unclear if this effect is due to L-arginine, other ingredients, or the combination. Additionally, the validity of the study is limited by the lack of blinding.
• Periodontitis. It is unclear if oral L-arginine is beneficial in patients with periodontitis. Details: Preliminary clinical research in patients with chronic periodontitis shows that using L-arginine aspartate (Yuria-Pharm, Ukraine) 1 gram three times daily orally for 10 days after scaling and root planing, modestly reduces bleeding on probing but not periodontal pocket depth, when compared with untreated controls (108926).
• Physical performance. It is unclear if oral L-arginine is beneficial for improving physical performance in older adults. Details: A small study in physically active females 65 years of age and older shows that taking L-arginine 8 grams as a single dose does not improve lower body strength, measured by knee flexion and extension tests, or functional performance, measured by sit-stand, tandem gait, and timed up-and-go tests, when compared with placebo (96812).
• Polycystic ovary syndrome (PCOS). Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a combination of N-acetylcysteine 1200 mg daily plus L-arginine 1600 mg daily for 6 months modestly improves menstrual function and decreases insulin resistance in patients with PCOS when compared to baseline (32094). The validity of these findings is limited by the lack of a comparator group.
• Postoperative infection. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Small clinical studies show that taking L-arginine, enterally or orally, either before or after surgery, in combination with fish oil, or with ribonucleic acid (RNA) and eicosapentaenoic acid (EPA), seems to reduce the rate of perioperative infection when compared with a control group. The risk of infection was 41% lower when compared to taking no arginine-based formulations. However, there is no good evidence to support the use of L-arginine alone for this purpose, and it is possible that this effect is due to the other ingredients or the combination of ingredients (5531,32174,32196).
• Postoperative recovery. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Small clinical studies show that taking L-arginine, enterally or orally, either before or after surgery, in combination with fish oil, or with ribonucleic acid (RNA) and eicosapentaenoic acid (EPA), seems to reduce the recovery time after surgery or serious illness when compared with a control group. This seems to be related to a reduced number of perioperative infections and improved wound healing. However, there is no good evidence to support the use of L-arginine alone for this purpose, and it is possible that this effect is due to the other ingredients or the combination of ingredients (5531,32174,32196). The effect of another combination product containing L-arginine is unclear. In one clinical study, taking a combination product (Abound, Abbott) containing L-arginine 7 grams, glutamine 7 grams, and hydroxymethylbutyrate 1.2 grams orally daily for 3 days before and 7 days after abdominal surgery did not reduce the incidence of wound infection or other complications when compared with placebo (99413). However, when a similar combination of L-arginine 14 grams, glutamine 14 grams, and hydroxymethylbutyrate 3 grams (Heallagen) was taken orally daily for one month before heart surgery, the length of hospital and ICU stay were reduced by about one day. Recovery, based on some but not all biochemical or other measurements, was also improved. However, there was no difference in risk of overall postoperative complications (110394). The discrepancies between these two studies may be related to differences in the dose or duration of the combination product and/or the type of surgery.
• Pressure ulcers. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Oral L-arginine has been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients show that administering an oral nutritional supplement enriched with L-arginine, zinc, and vitamin C improves ulcer healing when compared with a standard diet (31953,87173). A small preliminary clinical study in sedentary older adults in care facilities shows that giving an oral or enteral combination of L-arginine 7.4 grams, L-glutamine 7.4 grams, and hydroxymethylbutyrate (HMB) 1.3 grams (Abound, Abbott) daily for 20 weeks reduces median time to healing by 48 days when compared with standard care only (110396). Also, preliminary clinical research in patients living in long-term care facilities with grade II-IV pressure ulcers shows that taking an oral nutritional supplement enriched in protein, energy, L-arginine, vitamin C, and zinc daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
• Preterm labor. Small clinical studies suggest that oral L-arginine may prevent preterm labor. Details: A meta-analysis of three small studies shows that taking L-arginine 3-6.6 grams daily, starting in the second or third trimester usually until delivery, reduces the risk of preterm labor by about 50% when compared to control, usually placebo (110379).
• Pulmonary hypertension. It is unclear if oral L-arginine is beneficial in children with pulmonary hypertension related to beta-thalassemia. Details: Preliminary clinical research in children aged 6-18 years treated conventionally for pulmonary hypertension related to beta-thalassemia shows that taking L-arginine 0.1 mg/kg daily for 60 days reduces Doppler echocardiography pulmonary arterial pressure by 35% compared with baseline. This measurement was increased by up to 15% in children given conventional treatments only; however, a statistical comparison between these treatment groups was lacking (110391).
• Radiation dermatitis. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with head and neck cancer shows that taking a combination of L-arginine 7 grams, L-glutamine 7 grams, and hydroxymethylbutyrate (HMB) 1.2 grams (Abound, Abbott) in water twice daily from the first day of radiation to approximately 1 week after completion does not reduce the number of patients with severe dermatitis when compared with taking no supplement. However, there was a 34% reduction in the incidence of moderate dermatitis and the overall duration of dermatitis was reduced (96639).
• Restenosis. It is unclear if intravenous L-arginine helps to prevent restenosis after stent implantation. Details: Some clinical research suggests that intravenous and intracoronary infusion of L-arginine during stent implantation followed by oral L-arginine for 2 weeks does not reduce the risk of restenosis when compared with placebo (31925). However, local delivery of 6 mL of L-arginine 100 mg/mL for 15 minutes after stent deployment seems to reduce neointimal formation at 6 months after stent placement when compared with placebo (31883).
• Respiratory tract infections. Although there is interest in using oral L-arginine for respiratory tract infections, there is insufficient reliable information about the clinical effects of L-arginine for these conditions.
• Schizophrenia. It is unclear if oral L-arginine is beneficial in patients with schizophrenia. Details: A small clinical study shows that taking L-arginine 3 grams twice daily for 3 weeks, in conjunction with an individualized medication regimen, does not improve positive, negative, or depressive symptoms associated with schizophrenia when compared with taking the medication regimen alone (99264).
• Sexual dysfunction. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in females with sexual dysfunction who are taking oral contraceptives shows that taking a specific combination product (Lady Prelox, Horphag Research) containing L-arginine, maritime pine bark extract, L-citrulline, and rose hip extract daily for 8 weeks improves symptoms of sexual dysfunction by 18% when compared with a control group (91963). Taking the same product in a dose of 2 tablets twice daily for 8 weeks, in addition to the lifestyle management program, improves vaginal dryness in pre- and post-menopausal patients when compared with lifestyle management alone (103611). It is unclear if this effect is due to L-arginine, the other ingredients, or the combination.
• Sickle cell disease. Small clinical studies suggest that oral or intravenous L-arginine may modestly improve complications in patients with sickle cell disease. Details: Two small clinical studies in hospitalized children aged 3-19 years with sickle cell disease-related veno-occlusive crisis shows that administering L-arginine intravenously or orally 100 mg/kg three times daily for 5 days or until discharge reduces total opioid use by 26% to 54%, pain scores at discharge by 23%, and median length of hospital stay by about 36 hours when compared with placebo (97392,105063). Another very small clinical study in patients aged 13-63 years with sickle cell disease shows that taking L-arginine 0.1 grams/kg orally three times daily for 5 days reduces pulmonary hypertension when compared to baseline (11428).
• Stress. Oral L-arginine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in healthy adults shows that taking a single dose of L-arginine 50 mg plus L-theanine 200 mg modestly reduces stress associated with a stress-loading test when compared with placebo, but was no more effective than taking L-theanine alone (110393).
• Valproic acid-induced toxicities. Although there is interest in using intravenous L-arginine for valproic acid toxicity, there is insufficient reliable information about the clinical effects of L-arginine for this purpose. More evidence is needed to rate L-arginine for these uses.

(Read more about L-ARGININE)

POSSIBLY EFFECTIVE

• Athletic performance. Small studies show that taking a single oral dose of L-citrulline before anaerobic resistance exercise might reduce exhaustion and improve some performance measures. It is unclear if L-citrulline improves aerobic exercise performance; results are conflicting. Details: A meta-analysis of small clinical trials in healthy trained and untrained adults shows that taking L-citrulline prior to mostly anaerobic exercise marginally reduces perceived exhaustion and muscle soreness when compared with placebo (105965). Another meta-analysis including some of the same clinical studies shows that taking L-citrulline malate before exercise modestly increases performance on resistance exercises by an average of 6% when compared with placebo (105968). Individual studies show mixed benefit and mostly use a single dose of L-citrulline malate 8 grams 1 hour before exercise; other studies used L-citrulline 3.3-6 grams mixed in watermelon juice or sucrose water or L-citrulline malate 12 grams given 1-2 hours before exercise (94966,94957,97395,105965). L-citrulline has also been evaluated for use with aerobic exercise. A small study in healthy young adults taking L-citrulline 9 grams in 3 divided doses over 24 hours or as a single dose of 3 grams 3 hours before a treadmill test does not improve performance, but might reduce time to exhaustion, when compared with placebo (16473). Another small clinical study in healthy adults shows that taking about 6.8 grams (100 mg/kg) of L-citrulline daily for 5 days prior to a cycling trial does not improve time to exhaustion, oxygen uptake, or lactate levels when compared with taking 3 grams of glucose as placebo (105964). However, two small clinical trials in healthy males show that taking L-citrulline 2.4-6 grams daily for 7 days prior to a cycling test improves peak power by 9%, total work by 7%, and cycling time trial performance by 1.5% when compared with placebo (94954,94965). Differences in methods of testing athletic performance, the form and dose of L-citrulline used, and/or the duration of supplementation may explain the mixed results. L-citrulline has also been evaluated in combination with L-arginine. Research in male soccer players shows that taking L-citrulline 1.2 grams and L-arginine 1.2 grams daily for 7 days increases total power output over a 10-minute cycling test and improves subjective perceptions of exertion when compared with placebo (100956).

POSSIBLY INEFFECTIVE

• Sarcopenia. Oral L-citrulline does not seem beneficial for muscle strength in older adults when added to structured exercise. Details: Two small clinical studies in older adults show that taking L-citrulline in conjunction with structured exercise does not improve measures of strength, endurance, speed, or balance when compared with placebo and structured exercise (110146,110148). One study evaluated otherwise healthy adults aged 60-73 years taking L-citrulline 3 grams daily for 6 weeks (110146). The other study evaluated older adults with obesity and an average age of 68.5 years taking a specific L-citrulline product (Citrage) 10 grams daily for 12 weeks (110148).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Cardiovascular disease (CVD). Although there is interest in using oral L-citrulline for CVD, there is insufficient reliable information about the clinical effects of L-citrulline for this condition.
• Dementia. Although there is interest in using oral L-citrulline for dementia, there is insufficient reliable information about the clinical effects of L-citrulline for this condition.
• Diabetes. It is unclear if oral L-citrulline is beneficial in patients with diabetes. Details: A small clinical study in adults with diabetes who are taking metformin and sulfonylureas shows that adding L-citrulline (Bulk Supplements Co., Ltd.) 3 grams daily before breakfast for 8 weeks reduces average fasting blood glucose levels by 22 mg/dL and glycated hemoglobin by 0.7%, but does not affect lipid levels, when compared with taking a microcrystalline cellulose placebo (105963).
• Erectile dysfunction (ED). It is unclear if oral L-citrulline is beneficial in patients with ED. Details: A small non-randomized crossover study in adults with mild ED shows that taking L-citrulline 1.5 grams daily for one month improves erection hardness from "mild dysfunction" to "normal function" in 50% of patients, compared with only 8% of patients taking placebo (94956). L-citrulline has also been evaluated in combination with other ingredients. A clinical study in middle-aged males with ED shows that taking a specific combination product (Revactin, MD Concepts LLC) containing L-citrulline, muira puama, ginger root, and guarana twice daily for 3 months improves scores related to erectile function and intercourse satisfaction, but does not improve sexual desire or orgasmic function scores, when compared to baseline (103224). The validity of this study is limited by the lack of a placebo control, the use of per-protocol analysis, and a high dropout rate. In fact, 44% of patients withdrew in order to resume use of phosphodiesterase type 5 (PDE5) inhibitors. Another small clinical study in adults with ED living in Japan and using PDE5 inhibitors as needed shows that taking an adjunct 50 mL drink containing L-citrulline 800 mg, a specific fenugreek extract (Testofen) 600 mg, resveratrol 300 mg, and caffeine 40 mg daily for 14 days modestly improves erectile function and satisfaction with intercourse and orgasm when compared with a placebo drink (105966). The validity of this finding may be confounded by the "as needed" use of PDE5 inhibitors, which was not reported throughout the study. Further, in both combination studies, it is unclear if these effects are due to L-citrulline, other supplement ingredients, or the combination.
• Heart failure. Small clinical studies suggest that oral L-citrulline might be beneficial in patients with heart failure. Details: A very small clinical study in patients with heart failure with preserved ejection fraction (HFpEF) shows that taking L-citrulline malate 3 grams daily for 2 months decreases systolic pulmonary arterial pressure by 16% and improves the right ventricular ejection fraction after a stress test by 27% when compared to baseline (94962). The validity of this finding is limited by the lack of a control group. Another small open-label clinical study in patients with heart failure with reduced ejection fraction (HFrEF) shows that taking L-citrulline 3 grams daily for 4 months increases left ventricular ejection fraction by about 20% at rest and 13% during the stress test, and increases the right ventricular ejection fraction by about 15%, both at rest and with the stress test, when compared with no supplementation. This improved the heart failure functional class in 35% of patients (94955).
• Hypertension. It is unclear if oral L-citrulline is beneficial for lowering blood pressure. Details: A small clinical trial in adults with prehypertension shows that taking L-citrulline 2 grams with grape and cranberry polyphenols 548 mg daily for 6 weeks does not reduce mean ambulatory blood pressure when compared with a cellulose placebo (105969). A small crossover study in postmenopausal females with hypertension shows that taking L-citrulline 6 grams as a single dose does not improve systolic or diastolic blood pressure at rest or during 5 minutes of plantar flexion exercise when compared with placebo (110147). The effects of using L-citrulline regularly or in other patients with diagnosed hypertension is unclear.
• Lysinuric protein intolerance. Although there is interest in using oral L-citrulline for lysinuric protein intolerance, there is insufficient reliable information about the clinical effects of L-citrulline for this condition.
• Muscle strength. It is unclear if oral L-citrulline can improve muscle strength when used in conjunction with resistance training. Details: A clinical study in healthy resistance-trained adults shows that taking L-citrulline malate 2 grams daily for 8 weeks in conjunction with resistance training does not further increase lean mass or muscle strength, measured by leg and bench presses, when compared with a cellulose placebo and resistance training (97394).
• Muscular dystrophy. It is unclear if oral L-citrulline is beneficial in patients with Duchenne muscular dystrophy. Details: A small clinical study in adults with Becker muscular dystrophy, a milder form of Duchenne muscular dystrophy (DMD), shows that taking L-citrulline 5 grams with or without metformin 500 mg three times daily for 6 weeks improves 6-minute walking distance and decreases markers of muscle necrosis when compared to baseline (100975). A small clinical study in males aged 6.5-10 years with DMD shows that taking L-citrulline 2.5 grams with metformin 250 mg three times daily for 26 weeks does not appear to slow decline in motor function when compared with placebo. However, this combination seems to slow decline in children with more stable disease, defined as those who can walk at least 350 meters in 6 minutes (100976). The reasons for these disparate results are unclear, but they may be due to the different patient populations, disease severities, doses, and durations of therapy being studied.
• Postoperative pulmonary hypertension. It is unclear if oral citrulline prevents postoperative hypertension in children undergoing heart surgery. Details: A small clinical study in children 6 years of age and younger undergoing congenital heart surgery shows that higher blood levels of L-citrulline might protect against the incidence of postoperative hypertension. L-citrulline blood levels of at least 37 micromol/L immediately after surgery, and at 12, 24, and 36 hours postoperatively, protects against its development. However, supplementation with 1.9 grams/m2 during induction of anesthesia is not necessarily protective (16467).
• Post-polio syndrome. It is unclear if oral L-citrulline is beneficial for patients with this condition. Details: A small clinical study in adults with post-polio syndrome shows that taking L-citrulline 5 grams three times daily for 24 weeks does not improve 6-minute walking distance, motor function scores, muscle strength, or quality of life when compared with placebo (110149).
• Pulmonary hypertension. It is unclear if oral L-citrulline is beneficial in patients with pulmonary hypertension. Details: A very small clinical study in patients with idiopathic arterial pulmonary hypertension or pulmonary hypertension due to Eisenmenger syndrome shows that taking L-citrulline malate 1 gram three times daily for 2 weeks increases 6-minute walking distance by 44 meters and reduces mean pulmonary arterial pressure by 5% when compared with baseline (94963). The validity of these findings is limited by the small study size and the lack of a comparator group.
• Reye syndrome. Although there is interest in using oral L-citrulline for Reye syndrome, there is insufficient reliable information about the clinical effects of L-citrulline for this condition.
• Sickle cell disease. It is unclear if oral L-citrulline is beneficial in patients with sickle cell disease. Details: A small clinical study in children ages 10-18 years shows that taking L-citrulline 90-130 mg/kg daily in 2 divided doses for up to 9 months might reduce neutrophilia and other symptoms when compared with baseline (16463). The validity of these findings is limited by the small study size and the lack of a comparator group. More evidence is needed to rate L-citrulline for these uses.

(Read more about L-CITRULLINE)

LIKELY EFFECTIVE

• Dyslipidemia. Niacin prescription products, in doses of 500 mg or greater, are FDA-approved for primary hyperlipidemia and mixed dyslipidemia. Niacin dietary supplements are generally available in lower doses and have not been shown to improve lipid levels. Details: Prescription niacin is not routinely recommended as second-line therapy for patients who primarily need to decrease low-density lipoprotein (LDL) cholesterol. This is due to results from clinical trials showing no effect on cardiovascular related events or mortality (93346,93354,96208,96211,97308,97477,97336). However, niacin might be considered for patients with mixed hyperlipidemia or patients who need to increase high-density lipoprotein (HDL) cholesterol and lower triglycerides. Niacin might also be effective for isolated hypoalphalipoproteinemia (4817). The most pronounced increases in HDL and decreases in triglycerides occur at 1-1.5 grams daily, and the greatest LDL reduction occurs at 2-3 grams daily. Niacin reduces LDL cholesterol by up to 25%, compared with up to a 55% reduction with statins. High-dose niacin can also decrease triglycerides by 20% to 50%, increase HDL by 13% to 35%, decrease apolipoprotein B levels by 2% to 20%, and decrease lipoprotein(a) levels by 23% (4818,4886,4887,4888,4889,4890,12033,25567,93347,96213). The effects of higher dose extended-release niacin on LDL cholesterol and triglycerides appear to be greater in females than males (25565). Experts recommend maximizing statins first because they have the best evidence for improving cardiovascular outcomes (97477,97336,97337). However, if patients cannot reach their LDL goal with a statin alone or if they cannot tolerate a statin, niacin might be combined with other cholesterol-lowering drugs when diet and single-drug therapy are not adequately effective (8545,25566,93351,94191,97337). Adding low-dose niacin, 50 mg daily, to statin therapy has no additional benefit on lipid levels (8546). Population research in adults without dyslipidemia has also found that higher dietary intake of niacin for 3-10 years is associated with a 29% lower risk of developing dyslipidemia when compared with low dietary niacin intake (110493).
• Pellagra. Oral niacin is FDA-approved for the prevention and treatment of pellagra. Details: Population research has found that low consumption of niacin is associated with an increased risk of developing pellagra (25903). Taking niacin 500-1000 mg daily can resolve symptoms of pellagra within a week of treatment initiation (25904). However, niacinamide is sometimes preferred for this indication because it lacks the vasodilating effects of niacin (15,6243).

POSSIBLY EFFECTIVE

• HIV/AIDS-related dyslipidemia. Oral niacin seems to improve lipid levels in patients with dyslipidemia due to HIV/AIDs. Details: Small clinical trials in HIV patients with dyslipidemia associated with antiretroviral therapy shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated up to 2 grams daily for 14-48 weeks improves total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride levels when compared to baseline (25570,25902). Other preliminary clinical research in this population shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated to 2 grams daily for up to 2 years improves HDL cholesterol levels, but not total cholesterol or triglyceride levels, when compared with no treatment (25569).
• Metabolic syndrome. Oral niacin seems to improve lipid levels in patients with metabolic syndrome. Details: Clinical research shows that taking niacin (Niaspan, Abbott Laboratories) 2 grams daily orally for 16 weeks reduces triglyceride levels by 39 mg/dL and increases high-density lipoprotein (HDL) cholesterol by 5 mg/dL when compared to baseline in patients with metabolic syndrome. These improvements are significant when compared with placebo and are further increased when niacin is taken along with prescription omega-3 ethyl esters (Lovaza, GlaxoSmithKline Pharmaceuticals) 4 grams daily orally (93353). However, niacin does not seem to improve postprandial glucose levels in patients with metabolic syndrome (97333).

INEFFECTIVE

• Cardiovascular disease (CVD). Oral niacin does not seem to reduce cardiovascular-related events in patients with or without CVD. Details: Overall, niacin is not recommended for primary or secondary prevention of CVD. Most clinical trials and meta-analyses conducted prior to 2011 showed a reduction in cardiovascular-related events, cardiovascular-related mortality, and all-cause mortality in patients taking niacin alone or in combination with a statin or clofibrate for primary or secondary prevention of CVD (4847,7388,25095,25911,25912,93349). However, recent meta-analyses of these studies and additional moderate-to-high quality research conducted in over 39,000 patients show no effect of niacin on cardiovascular-related events, cardiovascular-related mortality, or overall mortality (93346,93354,96208,96211,97308). Additionally, one meta-analysis shows that patients taking niacin are twice as likely to report side effects when compared with placebo (96211). Furthermore, an analysis of blood from adults at high cardiovascular risk suggests that higher levels of circulating niacin terminal metabolites are associated with greater risk of major adverse cardiovascular events independent of traditional risk factors (113554).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alzheimer disease. It is unclear if oral niacin is beneficial for reducing Alzheimer disease risk. Details: Observational research has found that consuming higher amounts of niacin (17-45 mg daily) from food and supplements is associated with a slower cognitive decline and a lower risk of developing Alzheimer disease when compared with people who consume less niacin (14 mg daily) (12077). It is not known if the risk of Alzheimer disease is reduced by taking a stand-alone niacin supplement.
• Atherosclerosis. It is unclear if oral niacin prevents atherosclerosis progression. Details: Preliminary clinical studies show that taking niacin orally, in combination with colestipol for up to 2 years, might modestly reduce progression of atherosclerosis as measured by coronary lesions and carotid arterial intima-media thickness in high-risk males with existing coronary atherosclerosis (25906,25909,25910). However, niacin does not seem to be better than statins. One clinical study in adults with atherosclerosis and peripheral arterial disease shows that taking extended-release niacin 1500 mg, simvastatin 40 mg, and ezetimibe 10 mg daily for 2 years does not reduce atherosclerosis of the superficial femoral artery when compared with simvastatin alone (96208). Niacin has also not been shown to prevent cardiovascular events or mortality (93346,93354,96208,96211,97308).
• Athletic performance. It is unclear if oral niacin improves athletic performance. Details: Preliminary clinical research in untrained adult males shows that taking niacin 1000 mg orally once before a cycling test does not improve power, respiratory exchange ratio, or time to exhaustion when compared with placebo. In addition, these measures were significantly worse when compared with taking caffeine 5 mg/kg orally as a single dose (107942). Clinical research in untrained males also shows that taking a supplement containing niacin 40 mg, caffeine 400 mg, capsicum extract 66.7 mg, and black pepper extract 10 mg prior to exercising does not improve strength, time to exhaustion, or maximal oxygen consumption when compared with placebo (37873).
• Attention deficit-hyperactivity disorder (ADHD). Although there is interest in using oral niacin for ADHD, there is insufficient reliable information about the clinical effects of niacin for this condition.
• Cancer. It is unclear if dietary niacin is beneficial for cancer. Details: Population research in adults with cancer has found that high dietary niacin intake is associated with 49% and 27% lower risk of cancer-related mortality and all-cause mortality when compared with low dietary niacin intake. The same study also found that taking niacin supplements is associated with a lower risk of cancer-related mortality, but not all-cause mortality when compared with not taking niacin supplements (110496).
• Cataracts. It is unclear if oral niacin is beneficial for preventing cataracts. Details: Population research has found that high dietary intake of niacin is associated with a reduced risk of nuclear cataracts (6378). However, there is no reliable evidence that niacin supplements reduce the risk of cataracts.
• Cholera. It is unclear if oral niacin is beneficial for cholera. Details: One small clinical study in adults with severe cholera shows that taking 1-2 grams niacin orally reduces fluid loss in the stool by 31% to 47% in the first 16 hours when compared with control. The 2 gram dose seemed to result in a greater reduction in fluid loss than the 1 gram dose (4868).
• Erectile dysfunction (ED). It is unclear if oral niacin is beneficial in patients with ED and dyslipidemia. Details: Clinical research in patients with erectile dysfunction and dyslipidemia shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated to 1.5 grams nightly for a total of 12 weeks significantly improves penetration frequency and the maintenance of an erection after penetration when compared to baseline (25913). The validity of this finding is limited by the lack of a comparator group.
• Glaucoma. It is unclear if oral niacin is beneficial for preventing or treating glaucoma. Details: Population research has found that higher dietary intake of niacin is associated with a lower odds of having glaucoma. However, this association was not consistently present when adjusting for confounders. The effects of niacin supplementation on glaucoma have not been evaluated (107942).
• Hyperphosphatemia. It is unclear if oral niacin is beneficial for preventing high levels of phosphorus in the blood. Details: Preliminary clinical research in patients on maintenance dialysis who are no longer using phosphate binders shows that taking niacin 375-750 mg daily for 8 weeks reduces serum phosphorus levels by 2.1 mg/dL, increases calcium levels by 0.4 mg/dL, and decreases serum alkaline phosphatase when compared with baseline (25914). However, clinical research in hemodialysis patients with inadequate phosphate control despite using standard phosphate-binding therapy shows that taking niacin at the maximum tolerated dose, up to 1000 mg daily, for 12 weeks, does not decrease serum phosphate levels when compared with placebo (93341). It is possible that this latter study was too small to observe between-group differences in changes in serum phosphate levels.
• Hypertension. It is unclear if dietary niacin is beneficial for preventing hypertension. Details: Observational research in Chinese adults found a J-shaped association between dietary niacin intake and development of hypertension, with the lowest risk occurring in those with a daily dietary niacin intake of 14.3-16.7 mg (104934).
• Meniere disease. Although there is interest in using oral niacin for Meniere disease, there is insufficient reliable information about the clinical effects of niacin for this condition.
• Migraine headache. It is unclear if dietary niacin is beneficial for preventing migraine headaches. Details: Population research in adults has found that high dietary intake of niacin is associated with a 28% lower likelihood of having migraine headaches when compared with low dietary intake of niacin (110495). However, the effect of niacin supplementation on migraines has not been studied.
• Motion sickness. Although there is interest in using oral niacin for motion sickness, there is insufficient reliable information about the clinical effects of niacin for this purpose.
• Parkinson disease. It is unclear if oral niacin is beneficial for improving Parkinson disease symptoms. Details: Low-quality clinical research in adults with Parkinson disease shows that taking slow-release niacin 250 mg orally daily for 12 months improves Parkinson disease motor scores and fatigue scores by 17% and 26%, respectively, when compared with baseline (107944). However, higher quality clinical research shows that taking niacin 250 mg orally daily for 6 months does not improve Parkinson disease motor scores when compared with placebo (107943).
• Retinal vein occlusion. It is unclear if oral niacin is beneficial for improving retinal vein occlusion symptoms. Details: A small case series in patients with chronic retinal vein occlusion shows that taking niacin titrated to 500 mg three times daily for 1 year is associated with reduced central macular thickness and improved visual acuity in over 50% of patients when compared with a control group. The addition of prednisolone eye drops does not alter the outcomes of those taking niacin (96212). The validity of this finding is limited due to the retrospective nature of this study.
• Sickle cell disease. It is unclear if oral niacin is beneficial for improving lipid levels in patients with sickle cell disease. Details: A small clinical study in patients with sickle cell disease shows that taking extended-release niacin titrated to 1.5 grams daily for 12 weeks does not improve vascular function or increase high-density lipoprotein (HDL) or apolipoprotein A-I cholesterol levels when compared with placebo (96209).
• Schizophrenia. Although there is interest in using oral niacin for schizophrenia, there is insufficient reliable information about the clinical effects of niacin for this condition.
• Vertigo. Although there is interest in using oral niacin for vertigo, there is insufficient reliable information about the clinical effects of niacin for this condition. More evidence is needed to rate niacin for these uses.

(Read more about NIACIN)

POSSIBLY EFFECTIVE

• Congestive heart failure (CHF). Oral taurine may improve left ventricular function, heart failure-related symptoms, and exercise capacity in patients with CHF. Details: Taking taurine 2-6 grams in two or three divided doses daily for 6-8 weeks seems to improve left ventricular function (5248,5271,8221) and symptoms of heart failure (5271,5306,8221) when compared with placebo or coenzyme Q10 in patients with New York Heart Association (NYHA) functional class II to IV. Also, taking taurine 500 mg three times daily for 2 weeks seems to improve exercise capacity when compared with placebo in patients with heart failure (77176). Some patients with severe heart failure rapidly improve from NYHA class IV to II after 4-8 weeks of treatment. Improvement seems to continue for as long as taurine treatment is continued, up to one year (5306,8217,8218,8221).
• Hepatitis. Oral taurine may improve liver function in patients with acute or chronic hepatitis. Details: Several small clinical trials show that taking taurine 1.5-4 grams daily for up to 3 months improves liver function in patients with acute and chronic hepatitis when compared with placebo (10454,77114,77147).

POSSIBLY INEFFECTIVE

• Obesity. Oral taurine does not appear to improve body weight in adults who are obese or overweight. Details: A meta-analysis of 12 small clinical trials shows that taurine supplementation does not reduce body weight or body mass index (BMI) when compared with placebo. The studies included in this analysis evaluated taurine doses of 0.5-6 grams daily for 15 days to 6 months. Most of the patient populations evaluated in the included studies had liver or metabolic disorders; three studies specifically evaluated overweight or obese adults (104166). Additionally, a more recent clinical trial in a small group of females with obesity shows that taking taurine 1 gram three times daily along with a calorie-restricted diet for 8 weeks does not reduce body weight, BMI, or waist circumference when compared with calorie restriction alone (104167). In contrast, a very small study in adults with type 2 diabetes on antidiabetes medication shows that taking taurine 500 mg twice daily for 8 weeks reduces body mass, BMI, and body fat percentage when compared with control (112271). The validity of these effects is limited by the small sample size.

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Academic performance. It is unclear if oral taurine is beneficial to improve academic performance. Details: A very small clinical study in college entrance examinees over age 19 shows that taking a jelly containing taurine 3 grams daily for 14 days does not improve academic achievement when compared with baseline or placebo (110579). Due to its small size, this study may have been inadequately powered to detect a difference between groups.
• Age-related macular degeneration (AMD). Although there has been interest in using oral taurine for AMD, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Androgenic alopecia. Oral taurine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with androgenic alopecia or telogen effluvium shows that taking a combination product containing taurine, cysteine, methionine, iron, selenium, and hydrolyzed collagen (GFM Oral, Cantabria Labs) along with conventional therapy, consisting primarily of finasteride or minoxidil, daily for 12 weeks improves hair loss when compared with conventional therapy alone (111636). It is unclear if this effect is due to taurine, other ingredients, or the combination.
• Athletic performance. Research on the use of taurine for improving endurance or power output is limited and conflicting; however, it may improve performance by a small amount in some athletes. Details: Research is conflicting on the effects of taurine on athletic performance. Several clinical studies in trained and untrained athletes show that taking taurine 1-6 grams as a single dose before endurance exercise, or 3 grams daily for 8 weeks after endurance exercise, does not improve endurance or aerobic capacity when compared with placebo (77159,77203,95613,98334). However, a meta-analysis of 7 small clinical trials shows that taking taurine 1-6 grams daily for up to 2 weeks slightly improves endurance when compared with control. Also, preliminary studies in male cyclists, recreationally active males, Olympic-level athletes, and female athletes habituated to caffeine show that taking taurine 50 mg/kg or 1-6 grams one time 1.5-2 hours prior to a cycling test increases the time to exhaustion and peak, mean, and minimum power output but does not improve perceived exertion, fatigue index, heart rate, or anaerobic capacity when compared with placebo (101475,103211,112265,112269). The reasons for these discrepancies are unclear; the meta-analysis did not identify a dose or duration-related benefit. One small clinical trial shows that taking taurine 40 mg/kg improves muscle power in caffeine-deprived athletes who regularly use caffeine, but actually seems to worsen muscle power in athletes who do not regularly use caffeine (98335). Overall, it is not clear which population is most likely to benefit from taurine use (98337,98338). Study results are mixed when taurine has been evaluated in combination with other ingredients. One small study shows that taking a specific product containing taurine and caffeine (AdvoCare Spark) does not improve sprint performance in college athletes when compared with placebo (77195). However, other small studies of cyclists and boxers suggest that taking taurine in combination with a variety of other ingredients including B vitamins, caffeine, and glucuronolactone (Red Bull Energy Drink) or ginseng, kudzu, and soybean, may improve measures such as endurance, power, balance, or agility (37815,57945,110577,112269). It is unclear if the benefits seen in these studies are due to taurine, other ingredients, or the combinations.
• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral taurine for ADHD, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Autism spectrum disorder. Although there has been interest in using oral taurine for autism spectrum disorder, there is insufficient reliable information about the clinical effects of taurine for this purpose.
• Chemotherapy-induced nausea and vomiting (CINV). It is unclear if oral taurine is beneficial in patients with CINV. Details: One small clinical trial in patients with acute lymphoblastic leukemia receiving 6 months of chemotherapy shows that taking taurine (pure powder, Aviforme) 1000 mg twice daily, starting 6 hours after receiving chemotherapeutic agents, significantly improves CINV in 87.5% of patients. Other symptoms, such as reduced appetite and smell and taste impairment, are also improved in some patients (91512).
• Chemotherapy-induced nephrotoxicity. It is unclear if oral taurine is beneficial for preventing or treating chemotherapy-induced nephrotoxicity. Details: One small clinical trial in patients with acute lymphoblastic leukemia receiving 6 months of chemotherapy shows that taking taurine (pure powder, Aviforme) 1000 mg twice daily reduces plasma creatinine, urea, bilirubin, and liver enzymes after 4 months when compared with placebo. This suggests a protective effect against chemotherapy-induced nephrotoxicity and hepatotoxicity. A reduction in overall fatigue is also observed (95616).
• Cirrhosis. It is unclear if oral taurine is beneficial in patients with cirrhosis. Details: One small, uncontrolled clinical study in patients with cirrhosis shows that taking taurine 1 gram three times daily for 4 weeks reduces the severity and frequency of muscle cramps when compared to baseline (104165). Another small clinical trial in patients with cirrhosis shows that taking taurine 6 grams daily for 4 weeks reduces portal hypertension by 12%, compared with a 2% increase in the placebo group (98336). However, it is unclear if this is associated with a reduced risk for complications such as variceal bleeding and ascites.
• Cognitive function. It is unclear if oral taurine is beneficial for improving cognitive function; however, taking an energy drink (Red Bull Energy Drink) containing taurine and other ingredients may modestly improve some measures of cognitive function. Details: Levels of taurine decrease with age, but supplementation does not seem to have neuroprotective effects or cognitive benefits in the elderly (101471,110574,110578). In one small crossover study, taurine alone did not reduce errors in sleep-deprived individuals when compared with placebo (38154). However, taurine taken as part of an energy drink formulation containing taurine, caffeine, glucuronolactone, and B vitamins (Red Bull Energy Drink) improves focused and sustained attention, wakefulness, verbal reasoning, driving ability and quality, and reaction speed when compared with placebo (9899,38117,77088,77202). Preliminary clinical research in young adults also shows that consuming the Red Bull Energy Drink might improve attention and verbal reasoning, but does not seem to improve memory, when compared with placebo (9899,77088).
• Cystic fibrosis. Oral taurine may reduce steatorrhea in children with cystic fibrosis, but it does not seem to improve other measures of nutritional status. Details: Some small clinical studies in children with cystic fibrosis show that taking taurine 30-40 mg/kg daily for 7 days to 6 months might be useful as adjunctive therapy to reduce steatorrhea when compared with baseline or placebo (10455,77227,77231). However, it does not seem to improve growth, lung function, muscle protein breakdown, or other symptoms of cystic fibrosis (77224,77228). Also, adding taurine 500-1500 mg daily to treatment with ursodeoxycholic acid for up to one year does not improve liver function tests, fat absorption, or nutritional status in patients with cystic fibrosis and associated liver disease when compared with ursodeoxycholic acid alone (77246,77256).
• Delirium. It is unclear if oral taurine prevents delirium in patients in the intensive care unit. Details: A large clinical study of hospitalized adults in Iran who underwent liver transplantation shows that taking a specific taurine powder product (100% Taurine Amino Acid, MyProtein) 2 grams daily for 30 days post-transplant reduces the risk of delirium by 73% when compared with placebo. These results also suggest that for every four patients treated with taurine over placebo, one additional case of delirium is prevented. Patients who took taurine also had less time on the ventilator and shorter intensive care and hospital stays (110575). However, it is unclear if these effects are due to taurine or other factors since ventilator time and intensive care length of stay are risk factors for delirium.
• Diabetes. It is unclear if oral taurine is beneficial in patients with diabetes. Details: Plasma levels of taurine are reported to be lower in patients with diabetes than in healthy controls (101473). However, clinical research evaluating taurine for glycemic control is mixed (77074,103212). One small clinical trial in patients with type 2 diabetes shows that taking taurine 1 gram three times daily for 8 weeks reduces blood glucose, insulin resistance, total cholesterol, and low-density lipoprotein (LDL) cholesterol when compared with placebo (103212). Although there was no improvement in glycated hemoglobin (HbA1c), the study was not long enough to detect a meaningful reduction in HbA1c. Other preliminary clinical research shows that taking taurine 1-1.5 grams twice daily for 2-4 months does not affect fasting blood glucose, HbA1c, or insulin but may improve measures of insulin resistance in patients with type 2 diabetes when compared with placebo (77074,112271). However, taking taurine while following an exercise program 3 times weekly does appear to reduce fasting blood sugar and HbA1c when compared with exercise plus placebo (112271). The reasons for these discrepant findings are unclear; however, all the included studies were small and potentially inadequately powered to detect a difference in outcomes.
• Epilepsy. Although there has been interest in using oral taurine for epilepsy, there is insufficient reliable information about the clinical effects of taurine for this condition.
• Exercise-induced muscle soreness. Small clinical studies suggest that oral taurine may modestly improve exercise-induced muscle soreness. Details: One small clinical trial in healthy, untrained adults shows that taking taurine 2 grams in combination with branched chain amino acids (BCAAs) three times daily for 2 weeks reduces subjective muscle soreness by 37% when compared with placebo (77212). Another small clinical trial in young, untrained males shows that taking taurine (Taisho Pharmaceutical Co., LTD.) 2 grams three times daily after meals before exercise, and continuing for three days after exercise, reduces delayed onset muscle soreness (DOMS), but not creatine kinase levels, when compared with placebo (91513).
• Fatigue. It is unclear if oral taurine is beneficial for improving fatigue. Details: One small clinical trial shows that taurine seems to reduce fatigue when taken alone, but increases fatigue when taken in combination with caffeine (77202). However, an observational study in young adults has found that subjective scores for physical and mental fatigue do not seem to correlate with dietary taurine intake (101472). One small clinical trial shows that drinking 500 mL of an energy drink providing taurine 1 gram plus other ingredients including caffeine and B vitamins decreases measures of driving-related fatigue in a driving simulation when compared with placebo (91075).
• Helicobacter pylori. It is unclear if oral taurine can aid in the eradication of helicobacter pylori (H. pylori). Details: One clinical trial shows that taking taurine 500 mg twice daily in combination with conventional treatment for 6 weeks increases H. pylori eradication and shortens duodenal ulcer scarring time in patients with confirmed H. pylori infection when compared with conventional treatment alone (77145).
• Hyperlipidemia. It is unclear if oral taurine is beneficial for lowering lipid levels. Details: A meta-analysis of 12 small clinical trials in adults with various liver or metabolic disorders, but without a specific diagnosis of hyperlipidemia, shows that taurine supplementation reduces total cholesterol by 11 mg/dL and triglycerides by 13 mg/dL, but does not seem to improve low-density lipoprotein (LDL) cholesterol or high-density lipoprotein (HDL) cholesterol levels, when compared with placebo. The studies included in this analysis evaluated doses of 0.5-6 grams daily for 15 days to 6 months (104166). The benefits of taurine in adults with hyperlipidemia are unclear. The effect of taurine has also been investigated in combination with exercise. A very small study in adults with type 2 diabetes on antidiabetes medication shows that taking taurine 500 mg twice daily while participating in an exercise program 3 times weekly for 8 weeks reduces triglycerides, total cholesterol, and LDL cholesterol and increases HDL cholesterol when compared with exercise plus placebo (112271).
• Hypertension. Oral taurine may modestly reduce blood pressure in patients with hypertension; however, the long-term antihypertensive effects of taurine are unclear. Details: One clinical study in patients with elevated blood pressure or stage 1 hypertension shows that taking taurine 1.6 grams daily for 12 weeks reduces systolic blood pressure (SBP) by 5 mmHg and diastolic blood pressure (DBP) by 3 mmHg when compared with placebo. The benefit is seen after 8 weeks of continued supplementation (95614). A small clinical trial in patients with stage 2 hypertension (previously classified as borderline hypertension) shows that taking taurine 6 grams daily for 7 days reduces both SBP and DBP when compared to baseline (77229). The long-term effects of taurine on blood pressure are unclear. A meta-analysis of 12 small clinical trials in adults with various liver or metabolic disorders, but without a specific hypertension diagnosis, shows that taurine supplementation reduces SBP by 5 mmHg and DBP by 3 mmHg when compared with placebo. The studies included in this analysis evaluated doses of 0.5-6 grams daily for 15 days to 6 months (104166). Taurine is commonly found in energy drinks, and its effect on blood pressure when used in combination with other ingredients in the form of an energy drink has been evaluated. A small observational study in young adults suggests that drinking a specific combination product containing taurine 100 mg, caffeine, and group B vitamins (Redbull Energy Drink) reduces heart rate but does not change SBP or DBP when compared to baseline (112266). However, another small observational study in young healthy adults suggests that drinking a specific combination product containing taurine 2000 mg, caffeine, ginseng, glucuronolactone, inositol, guarana, L-carnitine, and B vitamins (Monster Energy Drink) increases both SBP and DBP by about 16 mmHg and raises heart rate by 17 beats per minute 15 minutes after consumption when compared to baseline. However, 90 minutes after consumption only DBP and heart rate remain elevated (112268). In both studies, the validity of the effects is limited by a lack of a comparator group. Additionally, it is unclear if the effects are due to taurine, other ingredients, or the combination.
• Infant development. Higher maternal intake of taurine from the diet may be linked to increased newborn length and weight; however, feeding taurine-containing formula to newborns does not appear to improve infant development. Details: One observational study has found a positive correlation between maternal dietary taurine intake and newborn length. In pregnant patients with high taurine intake (>120 mg/day), neonatal birth weight and length were significantly higher when compared with groups with lower taurine intake (101474). However, clinical research shows that administering infant formula containing taurine 45 mg/L for up to 12 weeks does not affect weight, length, head circumference, or behavior in preterm and full-term infants when compared with formula without taurine (77119,77216,77218,77239,77260).
• Iron deficiency anemia. It is unclear if oral taurine is beneficial in patients with iron deficiency anemia. Details: One small clinical trial in females with iron deficiency anemia shows that taking taurine 1000 mg plus ferrous sulfate 325 mg daily for 20 weeks improves hemoglobin concentrations, red blood cell counts, and serum ferritin levels when compared with ferrous sulfate plus placebo (77070).
• Muscular dystrophy. It is unclear if oral taurine is beneficial in patients with muscular dystrophy. Details: One very small crossover trial in patients with muscular dystrophy shows that taking taurine 100-150 mg/kg for 6 months improves the ability to relax muscles after voluntary use when compared with placebo (77235).
• Physical performance. It is unclear if oral taurine improves physical performance in older adults. Details: A small study in elderly females living in a care facility shows that taking taurine powder 1.5 grams daily for 14 weeks in addition to standardized exercise training may modestly improve some measures of physical fitness (i.e. agility, endurance) when compared to baseline. These measures were not improved in patients who took taurine but did not participate in exercise training or who participated in exercise training but did not take taurine (110574). The validity of these findings is limited by lack of randomization, blinding, and statistical comparison between groups.
• Postoperative recovery. It is unclear if oral taurine is beneficial for improving postoperative recovery. Details: One small clinical trial in patients recovering from surgery after a hip fracture shows that taking taurine 6 grams daily for 7 days after surgery does not improve morbidity and mortality outcomes after 1 year when compared with placebo (95615).
• Psychosis. It is unclear if oral taurine is beneficial in patients with psychosis. Details: One small clinical trial in adults up to 25 years of age with first-episode psychosis shows that taking taurine 4 grams daily for 12 weeks in combination with prescribed antipsychotics reduces positive psychotic symptoms, but not negative or cognitive symptoms, when compared with placebo (95612).
• Sleep deprivation. Oral taurine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a combination product containing taurine, caffeine, glucuronolactone, and B vitamins (Red Bull Energy Drink) reduces lane drifting and sleepiness and improves driving quality and reaction time during a car-driving simulator exercise in sleep-deprived individuals when compared with placebo (38117,77066). Other preliminary clinical research in sleep-deprived surgical trainees shows that taking taurine 2 grams in addition to caffeine 150 mg improves reaction time during performance of simulated laparoscopic surgery when compared with placebo, although error-making is not reduced (38154).
• Tourette syndrome. Oral taurine may improve tic severity in children with Tourette syndrome who are taking tiapride at a dose of 300 mg or less. Taurine may not be effective in children taking higher doses of tiapride. Details: One clinical trial in children 6-16 years of age with Tourette syndrome or other tic disorders shows that taking taurine along with tiapride reduces the severity of tics when compared with tiapride alone. For every 6 children taking taurine, one additional child saw a 60% or greater reduction in tic severity as measured on the Yale Global Tic Severity Scale when compared with placebo. However, taurine did not improve tic severity in children taking tiapride at a dose greater than 300 mg daily (103210). Taurine was taken in age-dependent doses of 2.4 grams daily in those 6-8 years, 3.6 grams daily in those 9-13 years, and 4.8 grams daily in those 14-16 years.
• Traumatic brain injury (TBI). It is unclear if oral taurine is beneficial in patients with a TBI. Details: A small clinical study of adults in Iran receiving treatment in the intensive care unit (ICU) following TBI shows that adding a specific taurine powder product (Nutricost) 30 mg/kg/day up to 3 grams daily to enteral nutrition for 14 days may modestly improve disease severity scores, but does not reduce days on the ventilator, ICU length of stay, or mortality at 30 days when compared with usual enteral nutrition (110573). Due to its small size, this study may have been underpowered to detect differences between groups. More evidence is needed to rate taurine for these uses.

(Read more about TAURINE)

EFFECTIVE

• Phenylketonuria (PKU). Oral tyrosine as a component of medical foods is recommended in people with PKU, a disorder in which phenylalanine cannot be endogenously metabolized into tyrosine. Details: Tyrosine is used as a component of medical foods for people with phenylketonuria (PKU) (7212,7213,7232). Current guidelines recommend that people with PKU maintain a diet low in phenylalanine and incorporate tyrosine as a component of medical foods to maintain normal blood levels of tyrosine (95108). Supplementation with additional tyrosine is recommended only for patients with consistently low blood levels of tyrosine despite using tyrosine-containing medical foods (95108). Routine supplementation with free tyrosine is not recommended for most patients because it can produce wide variations in tyrosine plasma concentrations and side effects (7212,95108). Tyrosine intake does not improve neuropsychological measures in patients with PKU (81503,91471,95108).

POSSIBLY EFFECTIVE

• Cognitive function. Oral tyrosine might improve cognitive function, particularly in patients exposed to stressors such as excessive cold, noise, or sleep deprivation. Details: Most research suggests that taking tyrosine orally improves cognitive function, particularly under stressful conditions. Small clinical studies in healthy adults show that taking tyrosine 100-300 mg/kg in the setting of exposure to stressors such as excessive cold, noise, or sleep deprivation improves cognitive performance measures, such as executive function and short-term memory, when compared with placebo (7215,81472,81476,81484,81501). Other small clinical studies in healthy patients show that taking tyrosine 2 grams may improve response time without detracting from performance and could improve some measures of cognitive response to conflict when compared with placebo (101082,111248). Some of these small studies may be inadequately powered to detect an effect on some cognitive function tests. Tyrosine has also been evaluated in combination with other ingredients for this purpose. A small clinical study in healthy adults with fatigue shows that taking tyrosine, serine, alanine, glutamate, and aspartate daily for 4 weeks improves measures of cognitive function including attention, spatial cognition, orientation, motivation, and time management when compared with placebo (111249). It is unclear if these effects are due to tyrosine, other ingredients, or the combination.
• Memory. Taking tyrosine orally seems to improve memory in patients exposed to stressors such as cold or those having to complete multiple tasks at once. Details: Small clinical studies in healthy adults show that taking tyrosine 150-300 mg/kg prior to acute exposure to stress that is cold-induced, noise-induced, or induced by multi-tasking improves memory performance when compared with placebo (81469,81477,81499,81501). However, tyrosine 150 mg/kg does not seem to improve memory in less stressful situations such as performing one simple task or testing when not exposed to cold (81469,81499).

POSSIBLY INEFFECTIVE

• Athletic performance. Oral tyrosine does not improve athletic performance when taken prior to exercise. Details: Clinical studies show that taking tyrosine orally prior to participating in treadmill or cycling exercises conducted at temperate temperatures or in the heat does not improve strength, endurance, or performance when compared with placebo (81471,81474,81504,91470,104403). Another very small clinical study in healthy males shows that taking a multi-ingredient pre-workout supplement containing L-tyrosine, beta-alanine, L-citrulline maleate, arginine alpha-ketoglutarate, L-taurine, and caffeine does not increase bench press strength endurance when compared with equivalent amounts of anhydrous caffeine (111250).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Alcohol use disorder. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with alcohol use disorder shows that taking a combination of tyrosine 900 mg, D,L-phenylalanine 1.5 grams, L-glutamine 300 mg, and L-tryptophan 400 mg daily along with a multivitamin supplement reduces withdrawal symptoms and decreases stress when compared with placebo (81552). It is unclear if these effects are due to tyrosine, other ingredients, or the combination.
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral tyrosine is beneficial for improving ADHD symptoms. Details: A very small clinical study shows that taking tyrosine does not improve symptoms of ADHD in children when compared with baseline (7209). Furthermore, another very small clinical trial in adults with ADHD shows that taking tyrosine daily for 8 weeks does not improve inattention when compared with baseline. Some patients might have transient symptom improvement after 2 weeks, but seem to acquire tolerance by 6 weeks (7210). The validity of these findings is limited by the small study size and lack of control groups.
• Cocaine dependence. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with cocaine dependence shows that taking L-tyrosine 1 gram in the morning and L-tryptophan 1 gram in the evening for 14 days does not reduce drug cravings or withdrawal symptoms when compared with placebo (81480).
• Dementia. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in patients with severe Alzheimer disease or multi-infarct dementia shows that taking a combination of tyrosine 4 grams, 5-HTP 800 mg, and carbidopa 100 mg orally daily does not improve clinical or psychological parameters in most patients when compared with baseline (918). The validity of this finding is limited by the small study size and a lack of control group.
• Depression. It is unclear if oral tyrosine is beneficial for improving major depressive disorder. Details: A small clinical study in patients with major depression shows that taking L-tyrosine 100 mg/kg daily for 4 weeks does not improve depressive symptoms when compared with placebo (7208).
• Erectile dysfunction (ED). Although there is interest in using oral tyrosine for ED, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Fatigue. Oral tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy adults with fatigue shows that taking tyrosine, serine, alanine, glutamate, and aspartate daily for 4 weeks does not improve subjective or objective measures of fatigue when compared with placebo (111249).
• Hypertension. It is unclear if oral tyrosine is beneficial for reducing hypertension of mild severity. Details: A very small clinical study in patients with mild essential hypertension shows that taking oral tyrosine 2.5 grams three times daily with meals for 2 weeks does not affect systolic or diastolic blood pressure when compared with control (81487).
• Mitochondrial myopathies. Although there is interest in using oral tyrosine for nemaline myopathy, a type of mitochondrial myopathy, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Narcolepsy. It is unclear if oral tyrosine is beneficial for improving narcolepsy symptoms. Details: A small clinical study in patients with narcolepsy shows that taking capsules containing tyrosine 3 grams orally three times daily for 4 weeks might reduce feelings of tiredness or drowsiness when compared with placebo, but the overall effect is not clinically significant. Tyrosine also does not seem to improve sudden muscle weakness, sleep paralysis, night-time sleep, sleep latency, or speed and attention after waking when compared with placebo (81482).
• Obesity. Oral tyrosine has only been evaluated for in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in overweight or obese patients shows that taking a supplement containing tyrosine 1.2 grams, cayenne 450 mg, green tea 1.5 grams, caffeine 150 mg, and calcium carbonate 3.89 grams daily for 8 weeks slightly reduces body fat mass by 0.9 kg when compared with placebo (81475). It is not clear if any potential benefit is due to tyrosine, other ingredients, or the combination.
• Opioid withdrawal. Oral tyrosine has only been evaluated for heroin withdrawal in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in Chinese males undergoing detoxification for heroin addiction shows that taking a combination of tyrosine 50 mg/kg, 5-HTP 200 mg, phosphatidylcholine 1200 mg, and L-glutamine 50 mg/kg daily for 6 days can reduce insomnia and withdrawal symptoms and improve mood when compared with placebo (88178). It is not clear if this effect is due to tyrosine, other ingredients, or the combination.
• Parkinson disease. Although there is interest in using oral tyrosine for Parkinson disease, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Premenstrual syndrome (PMS). Although there is interest in using oral tyrosine for PMS, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Schizophrenia. It is unclear if oral tyrosine is beneficial for improving schizophrenia symptoms. Details: A very small clinical study in patients with schizophrenia shows that taking L-tyrosine 10 grams daily in four divided doses along with molindone 150 mg daily for 3 weeks does not improve symptoms of schizophrenia when compared with taking molindone alone (81554).
• Sleep deprivation. It is unclear if oral tyrosine is beneficial for improving alertness in sleep deprived adults. Details: A small clinical study shows that taking tyrosine 150 mg/kg after the loss of a night's sleep seems to delay performance decline in psychomotor tests by about 3 hours when compared with placebo (7215). Another small clinical study in sleep-deprived patients shows that taking tyrosine 150 mg/kg improves memory, reasoning, and vigilance when compared with placebo at 5.5 hours after ingestion, but not at 1.5 hours. Tyrosine was less effective than taking amphetamine, phentermine, or caffeine (81472).
• Stress. Although there is interest in using oral tyrosine for stress, there is insufficient reliable information about the clinical effects of tyrosine for this condition.
• Wrinkled skin. Topical tyrosine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small study in patients with photodamaged skin shows that applying a topical preparation containing 10% vitamin C, acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (High Potency Serum, Cellex-C International Inc.) for 3 months to the face seems to improve fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the benefits are due to tyrosine, other ingredients, or the combination. More evidence is needed to rate the effectiveness of tyrosine for these uses.

(Read more about TYROSINE)

EFFECTIVE

• Imerslund-Grasbeck disease. Intramuscular vitamin B12 is effective for patients with this condition. Details: Administering intramuscular vitamin B12 (hydroxocobalamin) 1 mg daily for 10 days, followed by monthly injections for the remainder of a patient's life, is effective for treating familial selective vitamin B12 malabsorption (Imerslund-Grasbeck disease) (15,82862).
• Vitamin B12 deficiency. Administering vitamin B12 orally, intramuscularly, or intranasally is effective for preventing and treating vitamin B12 deficiency. Details: Vitamin B12 deficiency has varying definitions but is often defined as vitamin B12 (cobalamin) levels less than 180-200 pmol/L (or 240 pg/mL). Some believe that only intramuscular vitamin B12 is effective for treating vitamin B12 deficiency. However, clinical research shows that oral therapy increases cobalamin levels similarly to intramuscular administration, even in patients with pernicious anemia or malabsorption, if a high enough dose is given (2909,2911,2915,9335,82832) (82836,82949,82860,103976,103972,107141,107144). Some evidence suggests that the most effective oral dose is between 647-1032 mcg daily (13106). However, in certain situations, intramuscular treatment might be more appropriate. Guidelines by the British Committee for Standards in Hematology recommend only intramuscular vitamin B12 for initial treatment of severe vitamin B12 deficiency in patients with pernicious anemia, malabsorption disorders, or neurological involvement (94722). Intramuscular vitamin B12 is also appropriate in patients with diarrhea or vomiting and those likely to be nonadherent (103972). Vitamin B12 deficiency is especially common in older adults, primarily due to lack of intrinsic factor and malabsorption (2915,2919,9335). Daily supplementation with vitamin B12 50-100 mcg might be needed to correct deficiency (10126), while daily doses of 25-37.5 mcg help to maintain normal levels over time (9335). In addition to supplements, foods such as milk and bread fortified with vitamin B12 can be used and are approximately 55% to 60% absorbed by people over 60 years of age (10124). Vitamin B12 deficiency is also common in patients that have had gastric surgery, including gastrectomy and bariatric surgery (107144,107145). Taking vitamin B12 in the doses found in multivitamins or generic vitamin B supplements does not seem to prevent vitamin B12 deficiency following bariatric surgery (107145). However, taking methylcobalamin 500 mcg daily is beneficial for treating vitamin B12 deficiency associated with a total gastrectomy and taking cyanocobalamin 5000 mcg daily is beneficial for preventing vitamin B12 deficiency following gastric bypass (107144). Other people at risk for vitamin B12 deficiency include strict vegetarians who eat no animal products (vegans) and people with increased vitamin B12 requirements associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, and hepatic and kidney disease. Moderate consumption of animal products may not be sufficient to restore and maintain vitamin B12 levels, especially in adolescents who had consumed macrobiotic (vegan type) diets for the first 6 years of life. High dietary intake of vitamin B12 or supplements is usually needed in order to restore and maintain optimal vitamin B12 levels in these adolescents (10125).

LIKELY EFFECTIVE

• Cyanide poisoning. Intravenous hydroxocobalamin (Cyanokit) is likely effective as an antidote for patients with suspected or known cyanide toxicity due to inhalation, ingestion, or skin exposure. Details: Treatment of cyanide poisoning with hydroxocobalamin (Cyanokit) up to 10 grams has been approved by the US Food and Drug Administration (FDA) and recommended by the Australian Resuscitation Council (82870,82905,82906). Hydroxocobalamin is also FDA-approved for treating cyanide toxicity during pregnancy (82904).

POSSIBLY EFFECTIVE

• Canker sores. Sublingual or topical vitamin B12 seems to reduce canker sore symptoms. Details: Clinical research in patients with canker sores shows that applying a topical ointment containing vitamin B12 500 mcg in four divided doses daily for 2 days reduces pain levels by 80% when compared with a control ointment not containing vitamin B12 (96176). Other preliminary clinical research shows that taking vitamin B12 1000 mcg sublingually daily for 6 months reduces the duration of canker sore outbreaks, the number of ulcers, and level of pain when compared with placebo in patients with normal vitamin B12 levels (17242).
• Hyperhomocysteinemia. Oral vitamin B12 in combination with folic acid, and sometimes with vitamin B6, reduces homocysteine levels. Details: While folic acid 0.5-5 mg daily lowers fasting homocysteine levels by an average of 25%, adding vitamin B12 0.5 mg daily produces an additional decrease of about 7% on average (6883,9400,9401,9405,9409,50145,107136). Vitamin B12 in combination with folic acid and other vitamins also reduces homocysteine levels in patients with kidney failure, sickle cell disease, and those receiving nitrous oxide general anesthesia (1489,6883,6884,7289,7881,9324,9414,9415,9416,9481,82941). Some researchers recommend routine use of vitamin B12 with homocysteine-lowering regimens to avoid the risk of neuropathy in people with undetected vitamin B12 deficiency (9405). Using vitamin B12 alone has a limited effect on homocysteine levels, and probably only in those people with vitamin B12 deficiency (2147,9410,9512). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,2147,3323,9402,9405,9408,9409). Clinical research suggests that supplementation with folic acid, pyridoxine, and vitamin B12 decreases homocysteine levels and reduces the atherosclerosis progression in patients at risk for atherosclerosis when compared with placebo (50133,50056,82806). However, other research suggests that elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50%, and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9400,9405,9409,96417). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem improve endothelial function or help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50373,50314,97619). There is also some debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials including over 44,000 patients shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo in patients at risk or with a history of CVD (97619). Also, a meta-analysis in adults with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and vascular death by 11% when compared with placebo (107136).
• Postherpetic neuralgia. Subcutaneous injections of vitamin B12 seem to reduce postherpetic neuralgia symptoms. Details: Clinical research in patients with subacute herpetic neuralgia shows that subcutaneous injection of vitamin B12 (methylcobalamin) 1000 mcg six times weekly for 4 weeks reduces pain when compared with oral vitamin B12 or subcutaneous lidocaine (90394). Another clinical study shows that administering local subcutaneous injections of methylcobalamin 1000 mcg plus lidocaine up to 20 mg daily for 12 injections over 14 days, starting within 7 days of the onset of subacute ophthalmic herpetic neuralgia, decreases the mean pain score by 63% to 79% when compared with intravenous lidocaine and intramuscular methylcobalamin. Less than 2 patients need to be treated to achieve a pain reduction to ≤3 out of 10. Healing of rash, itching, numbness, and tingling were also improved (96175). Additional clinical research in patients with postherpetic pain and itching shows that this same dosing regimen of subcutaneous vitamin B12 reduces pain and analgesic requirements when compared to baseline (90396).

POSSIBLY INEFFECTIVE

• Age-related cognitive decline. Oral vitamin B12 does not seem to improve cognitive function in older adults when used alone or in combination with other B vitamins. Details: Taking vitamin B12 100-1000 mcg plus folic acid 400-2000 mcg, with or without vitamin B6 3-50 mg, daily for up to about 2 years does not seem to improve tests of cognitive function in adults aged 65 or older, most of whom do not report cognitive impairment at baseline (14392,50225,50510,90392,107140). Also, supplementation with vitamin B12 does not seem to improve cognitive function in elderly individuals with low vitamin B12 levels (12305).
• Alzheimer disease. Oral vitamin B12, when used in combination with other B vitamins, does not seem to improve cognitive function in patients with Alzheimer disease. Details: Clinical research in patients with probable Alzheimer disease using routine medication shows that taking vitamin B12 1 mg, folic acid 5 mg, and vitamin B6 25 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, a meta-analysis of clinical research in elderly adults with mild cognitive impairment or dementia shows that taking vitamin B12, usually with other B vitamins, does not improve cognitive function (50510). Observational research has also found that higher vitamin B12 intake over 3 years in a population consuming a folate-fortified diet is not associated with a decreased risk of developing Alzheimer disease (15270). In contrast, preliminary clinical research in patients with probable Alzheimer disease who are not consuming a folate-fortified diet shows that taking vitamin B12 50 mcg daily plus folic acid 1.2 mg daily for 6 months modestly improves some measures of cognitive performance and decreases levels of homocysteine when compared with placebo (107150). More research is needed to determine if any changes in this latter study are clinically relevant.
• Cataracts. Oral vitamin B12 does not seem to reduce cataract development. Details: Clinical research in women with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg daily, vitamin B6 50 mg daily, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts and seems to increase the risk of cataract extraction by 28% when compared with placebo (96149).
• Circadian rhythm sleep disorders. Oral vitamin B12 does not seem to improve sleep disorders. Details: Oral vitamin B12 (methylcobalamin) does not seem to be effective for treating delayed sleep phase syndrome. Methylcobalamin 0.5-1 mg three times daily, with or without bright light therapy, also does not seem to help people with primary circadian rhythm sleep disorders (1344,1345,1346,1347,1348).
• Cognitive impairment. Oral vitamin B12 does not seem to be beneficial for older adults with cognitive impairment. Details: A meta-analysis of clinical research in elderly adults with mild cognitive impairment or dementia shows that taking vitamin B12, usually with other B vitamins, does not improve cognitive function (50510). One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374).
• Fall prevention. Oral vitamin B12 does not seem to reduce the risk of falls. Details: Clinical research shows that taking B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg, daily for 2 years does not prevent falls when compared with placebo in elderly individuals also taking vitamin D (96148).
• Osteoporosis. Oral vitamin B12 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in elderly patients or patients with a history of cerebrovascular disease shows that taking vitamin B12 500 mcg and folic acid 0.4-2 mg, with or without vitamin B6 25 mg, daily for 2-3 years does not seem to reduce the risk for osteoporotic fractures when compared with placebo (90377,90393). A 5-7 year follow-up of this research has also found no benefit (103981).
• Physical performance. Oral vitamin B12 does not seem to improve physical performance in older adults. Details: Clinical research shows that taking B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg, daily for 2 years does not increase hand strength or improve performance such as walking when compared with placebo in elderly individuals also taking vitamin D (96148).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related macular degeneration (AMD). Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B12 1000 mcg, folic acid 2.5 mg, and vitamin B6 50 mg daily, reduces the risk of developing AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or at least three risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B12, other ingredients, or the combination.
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if high-dose intramuscular vitamin B12 improves the prognosis of ALS. Details: A clinical study in patients with ALS symptoms for 3 years or less shows that intramuscular vitamin B12 (methylcobalamin) 25-50 mg twice weekly for 3.5 years does not slow functional decline or increase the time until ventilation or death when compared with placebo. However, other clinical research in patients with early-stage ALS shows that intramuscular methylcobalamin 50 mg twice weekly for 16 weeks is associated with slower functional decline and a longer period of time until death or full ventilation when compared with placebo (104947,111556). These effects seem to be particularly notable in fine and gross motor skills, but not bulbar or respiratory functions. Furthermore, vitamin B12 and riluzole slowed clinical progression of ALS more than riluzole alone (111556).
• Angioplasty. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B12 400 mcg, folic acid 1 mg, and vitamin B6 10 mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412,34540). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, pyridoxine, and vitamin B12 followed by oral administration of folic acid 1.2 mg, pyridoxine 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151,34540). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B12, other ingredients, or the combination.
• Anxiety. Although there is interest in using oral vitamin B12 for anxiety and panic attacks, there is insufficient reliable information about the clinical effects of vitamin B12 for these uses.
• Asthma. Although there is interest in using oral vitamin B12 for asthma, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
• Atherosclerosis. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with intermediate risk for coronary heart disease shows that taking vitamin B12 100 mcg, aged garlic extract 250 mg, folic acid 300 mcg, vitamin B6 12.5 mg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B12, other ingredients, or the combination.
• Atopic dermatitis (eczema). It is unclear if topical vitamin B12 reduces the severity of eczema. Details: Preliminary clinical research shows that applying a specific topical vitamin B12 0.07% cream (Regividerm) twice daily reduces the extent and severity of atopic dermatitis when compared with placebo (15765).
• Attention. Although there is interest in using oral vitamin B12 for improving attention and focus, there is insufficient reliable information about the clinical effects of vitamin B12 for this use.
• Cancer. It is unclear if oral vitamin B12 reduces overall cancer risk when used in combination with other B vitamins. Details: An ancillary clinical study in middle-aged and elderly adults with cardiovascular disease shows that taking a combination of vitamin B12 (cyanocobalamin) 0.02 mg, folic acid 0.56 mg, and vitamin B6 3 mg, with or without eicosapentaenoic acid (EPA) 400 mg plus docosahexaenoic acid (DHA) 200 mg, for a median of 4.7 years does not reduce the risk of cancer when compared with placebo (90666). An additional secondary analysis of clinical research in patients recovering from stroke or transient ischemic attack shows that taking vitamin B12 500 mcg, folic acid 2 mg, and vitamin B6 25 mg daily for around 3.4 years does not reduce the risk of cancer when compared with placebo (90378). The validity of these findings is limited because the studies were not designed nor adequately powered to test for cancer risk.
• Cardiovascular disease (CVD). Oral vitamin B12, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly reduce the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B12 in combination with folic acid and/or vitamin B6 does not seem to reduce the risk for secondary death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, other research shows that taking vitamin B12 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). It is unclear which specific combination of B vitamins, if any, might be optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
• Cervical cancer. It is unclear if oral vitamin B12 reduces cervical cancer risk. Details: Some epidemiological evidence has found that increasing vitamin B12 intake from dietary and supplement sources, along with folic acid, thiamine, and riboflavin, might decrease the risk of precancerous cervical lesions (11074). Also, an analysis of two case control studies has found that increased intake of vitamin B12 is associated with a 75% reduced odds of cervical cancer (34609).
• Chemotherapy-induced peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients receiving chemotherapy shows that a combination of B vitamins that includes vitamin B12 (cyanocobalamin) 1000 mcg, taken daily starting one week prior to treatment and finishing 12 weeks after treatment is completed, does not prevent peripheral neuropathy when compared with placebo (96173).
• Child development. It is unclear if oral vitamin B12 is beneficial for child development. Details: Population research has found that daily dietary intake of less than 2.26 mcg vitamin B12 in the third trimester of pregnancy is associated with an increased risk of poorer outcomes in the offspring for some measures of speech and mathematics ability, including vocabulary at 24 months, combining words at 38 months, speech intelligibility at 6 years, and math comprehension between ages 8-11 years, when compared with dietary intakes of at least 2.26 mcg daily. There was no association between prenatal vitamin B12 intake and reading or spelling abilities, vocabulary at other ages, or full-scale Intelligence Quotient (IQ) at ages 8 or 15 (107143). Furthermore, a very large clinical study in infants of pregnant adults, 71% of whom were deficient in vitamin B12 at baseline, shows that taking vitamin B12 50 mcg daily starting in early pregnancy (<15 weeks gestation) until 6 months postpartum does not improve neurodevelopment as measured by language, motor, socioemotional, or cognitive scores at 12 months old and may worsen early motor performance at 8-12 weeks when compared with placebo. However, the negative effects on motor performance resolved by 6 and 12 months of age (112431).
• Child growth. Oral vitamin B12 taken by pregnant adults does not seem to be beneficial for infant growth. Details: A very large clinical study in infants of pregnant adults, 71% of whom were deficient in vitamin B12 at baseline, shows that taking vitamin B12 50 mcg daily starting in early pregnancy (<15 weeks gestation) until 6 months postpartum does not improve the infant's linear growth, length, or weight at 12 months of age (112431).
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral vitamin B12 reduces the risk of COPD. Details: Clinical research in patients with COPD shows that taking vitamin B12 500 mg daily for 8 weeks modestly improves endurance on the cycle ergometer, but does not improve oxygen consumption, when compared with placebo (96172).
• Cognitive function. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy, middle-aged adults shows that taking a combination product containing vitamin B12, other B vitamins, bacopa, and gingko biloba twice daily for 12 weeks does not improve measures of memory, attention, cognition, mood, or stress reactivity when compared with placebo (111334).
• Colorectal cancer. It is unclear if oral vitamin B12 reduces colorectal cancer risk. Details: Some epidemiological evidence has found that increased dietary intake of vitamin B12 is associated with a reduced risk of developing colorectal cancer (90383). However, preliminary clinical research shows that taking vitamin B12 1 mg, folic acid 2.5 mg, and vitamin B6 50 mg daily for up to 7.3 years does not reduce the risk of colorectal adenoma in females at high risk for cardiovascular disease (90389). Furthermore, a secondary analysis of clinical research in elderly patients suggests that taking vitamin B12 500 mcg and folic acid 400 mcg daily for 2 years might increase the risk of colorectal cancer when compared with placebo (90393).
• Coronavirus disease 2019 (COVID-19). It is unclear if oral vitamin B12 is beneficial for patients with COVID-19. Details: A small observational study in hospitalized patients with COVID-19 pneumonia has found that higher plasma vitamin B12 levels may be associated with an increased risk of transfer to intensive care or death than lower plasma levels. However, when multivariate regression was conducted, only patient age was associated with worsened outcomes. Additionally, the total study population was small, with only nine of 49 patients experiencing the worsened outcomes (107138).
• Dementia. It is unclear if oral vitamin B12 reduces the risk of developing dementia. Details: A large cohort of Danish adults has found that vitamin B12 levels or intake does not seem to impact the risk of developing Alzheimer disease or other dementias (104922). However, vitamin B12 might be beneficial in specific patient populations. A small observational study in patients with Parkinson disease has found that higher vitamin B12 levels (648.5 ng/L) are associated with a lower risk of developing dementia when compared with lower vitamin B12 levels (452 ng/L) (103975). It is not yet known if supplementation with vitamin B12 reduces the risk for dementia in these patients.
• Depression. It is unclear if oral vitamin B12 is beneficial for reducing depression risk. Details: A meta-analysis of epidemiological research has found that the highest dietary intake of vitamin B12 is associated with a 14% reduced risk of depression. However, in a sub-analysis, this association was not significant in males (107133). In contrast, one epidemiological study in older males included in the analysis has found that daily dietary intake of at least 4.79 mcg vitamin B12 is linked with a 58% lower risk of depression when compared with daily intake of less than 3.16 mcg. In this study, this inverse association was not observed in females (96168). Other observational research has found that low-normal serum vitamin B12 levels are associated with a 3.8 times increased risk for depression during pregnancy when compared with normal vitamin B12 levels (102384). It is unclear if increased intake of vitamin B12 through the diet or supplements reduces the risk for depression or is beneficial for treating symptoms of depression in any population. However, a meta-analysis of clinical research in elderly populations shows that supplementation with vitamin B12 100-1000 mcg daily, usually in combination with folic acid 400-2000 mcg daily, does not reduce symptoms of depression. Most individuals in these studies were not specifically diagnosed with depression (107140).
• Diabetes. It is unclear if oral vitamin B12 improves glycemic indices or prevents loss of skeletal muscle in patients with diabetes. Details: A small clinical study in patients with diabetes in India who are stabilized on metformin and/or a sulfonylurea shows that taking vitamin B12 (methylcobalamin) 500 mcg with or without folic acid 5 mg daily for 8 weeks seems to reduce glycated hemoglobin (HbA1C) by 1.3% to 1.5%, compared with a 0.3% increase with placebo (104917). This study is limited due its small sample size and lack of blinding. In elderly adults with type 2 diabetes, population research has found a lower dietary intake of vitamin B12 (average of 11.2 mcg daily) in individuals with a loss of skeletal muscle mass of at least 1.2%, compared with an average intake of 13.4 mcg daily in those with a skeletal muscle mass loss of less than 1.2%. However, further analysis determined that any relationship between vitamin B12 intake and loss of skeletal muscle mass was only significant in individuals with insufficient energy intake overall (107151).
• Diabetic neuropathy. Small clinical studies suggest that oral vitamin B12 may modestly improve pain in patients with diabetic neuropathy. Details: Two small clinical studies in patients with diabetic peripheral neuropathy show that taking vitamin B12 (methylcobalamin) 1-1.5 mg for 4-12 months modestly improves pain when compared with baseline or placebo (82841,104923). Some research also shows that vitamin B12 may be beneficial in combination with other ingredients. Studies have evaluated products containing vitamin B12 (methylcobalamin or cyanocobalamin), benfotiamine, and vitamin B6 daily for 9-12 weeks (82931,82939); and vitamin B12 (methylcobalamin) 2 mg, folic acid (L-methylfolate) 3 mg, and vitamin B6 (pyridoxal-5'-phosphate) 35 mg (Metanx; Pamlab) daily for 24 weeks (90375).
• Diarrhea. It is unclear if oral vitamin B12 is beneficial for reducing diarrhea in children. Details: Preliminary clinical research in children aged 6-30 months from low- and middle-income countries shows that taking vitamin B12 at twice the recommended dietary allowance, with or without folic acid, does not reduce the risk for diarrhea when compared with placebo (90391).
• Fatigue. It is unclear if intramuscular vitamin B12 is beneficial for improving well-being in those with fatigue or tiredness. Details: A small crossover trial in patients complaining of tiredness or fatigue shows that receiving intramuscular injections of vitamin B12 (hydroxocobalamin) 5 mg twice weekly for 2 weeks seems to improve general well-being and happiness, and has a trend toward improving fatigue, when compared with placebo (10127). The validity of this study is limited by a large drop-out rate and unstandardized outcome measures.
• Hearing loss. Oral vitamin B12 has only been evaluated in combination with adenosine triphosphate; its effect when used alone is unclear. Details: A small observational study in adults with idiopathic sudden sensorineural hearing loss has found that taking vitamin B12 1.5 mg with adenosine triphosphate 300 mg daily for 8-16 weeks is associated with modestly reduced hearing loss at 4-6 months after starting treatment when compared with taking the combination for less than 8 weeks (104924). This finding is limited due to its observational nature and lack of a control group.
• Hepatitis C. It is unclear if intramuscular vitamin B12 is beneficial for sustaining viral response in patients with chronic hepatitis C infection. Details: A small clinical study in patients with chronic hepatitis C infection shows that intramuscular vitamin B12 (cyanocobalamin) 5000 mcg every 4 weeks along with standard care improves sustained viral response when compared with standard of care alone (90386).
• Hypertriglyceridemia. It is unclear if oral vitamin B12 is beneficial for reducing triglyceride levels. Details: Some evidence shows that taking vitamin B12 7.5 mcg with fish oil 5 grams might be superior to fish oil alone when used daily to reduce total serum cholesterol and triglycerides. This suggests vitamin B12 might have an independent effect in lowering serum cholesterol and triglycerides, but further investigation is needed to confirm this effect (8694).
• Hypotension. It is unclear if oral vitamin B12 is beneficial for treating hypotension. Details: A meta-analysis of 3 observational studies in patients hospitalized with hypotension secondary to cardiac surgery vasoplegia suggests that administration of intravenous vitamin B12 (hydroxocobalamin) is associated with an 8 mmHg higher mean arterial pressure (MAP) at 1 hour but no change in vasopressor dosage at 1 hour or mortality rate when compared with methylene blue (112264). The validity of these findings is limited by the inclusion of only retrospective studies.
• Infant development. It is unclear if taking oral vitamin B12 during pregnancy is beneficial for improving infant development. Giving oral vitamin B12 to infants does not seem to be beneficial. Details: Clinical research shows that supplementation with vitamin B12 50 mcg daily from less than 14 weeks gestation until 6 weeks postpartum does not improve cognitive development in infants by 9 months of age when compared with placebo (96174). When these children were evaluated at 30 months of age, a very small benefit of vitamin B12 on expressive language was identified; however, there was no effect on cognition, receptive language, fine motor skills, or gross motor skills (100169). It is unknown whether a longer duration of postpartum supplementation or supplementation in specific populations might be beneficial. Vitamin B12 supplementation in infants has also been evaluated. A large clinical trial in marginally stunted Nepalese infants aged 6-11 months shows that giving vitamin B12 (cyanocobalamin) 2 mcg daily for 12 months reduces homocysteine levels, but does not improve motor or cognitive development, when compared with placebo (104926).
• Inflammatory bowel disease (IBD). Although there is interest in using oral vitamin B12 for IBD, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
• Lung cancer. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: The association between vitamin B12 and lung cancer is unclear. Some population research found no relationship between blood levels of vitamin B12 and lung cancer (9454). However, other observational research involving over 5,000 case-control pairs found that higher vitamin B12 levels are linked with an increased risk for lung cancer (102383). It is unclear if increased intake of vitamin B12, either through the diet or supplementation, directly affects the risk of lung cancer.
• Male infertility. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A retrospective study in adult males with idiopathic and varicocele-related infertility suggests that taking a combination product containing vitamin B12 1.5 mcg, L-carnitine, acetyl L-carnitine, citric acid, selenium, coenzyme Q10, vitamin C, zinc, and folic acid (Proxeed Plus) twice daily for 6 months is associated with improvements in ejaculate volume, sperm count, sperm concentration, total motility, and progressive motility in patients with idiopathic infertility when compared to baseline. However, improvement in sperm morphology was lacking. Furthermore, patients with more severe varicocele seem to benefit most, especially with regard to progressive motility (111296). The validity of these findings is limited by a lack of comparator group. Further, it is unclear if these effects are due to vitamin B12, other ingredients, or the combination.
• Mastalgia. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with mastalgia shows that taking a combination of vitamin B12 as methylcobalamin 100 mg, gamma-linolenic acid, and vitamin C daily for 12 weeks does not improve the proportion of patients with minimal or no pain when compared with placebo (111059).
• Multiple sclerosis (MS). Although there is interest in using oral vitamin B12 for MS, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B12 is beneficial for NAFLD. Details: A small clinical study in adults with NAFLD shows that taking vitamin B12 1000 mcg daily for 12 weeks reduces serum levels of homocysteine but has no effect on serum aminotransferases, measures of steatosis, fibrosis scores, fasting blood glucose, serum insulin, measures of insulin resistance, triglycerides, low-density lipoprotein (LDL) cholesterol, or high-density lipoprotein (HDL) cholesterol when compared with placebo (111555).
• Pancreatic cancer. It is unclear if oral vitamin B12 is beneficial for reducing the risk of pancreatic cancer. Details: Most population research has found that increased intake of vitamin B12, as a supplement or in the diet, is not associated with a reduced risk of pancreatic cancer (9327,104927). However, a small, retrospective population study in which smoking and non-smoking adults recalled past eating habits found that increased dietary intake of vitamin B12 is associated with a 33% reduction in pancreatic cancer risk (97976). These conflicting findings may be related to study methodology, as well as the age, gender, or smoking status of the included patients.
• Periodontitis. Although there is interest in using oral vitamin B12 for periodontitis, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
• Peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a specific product containing vitamin B12 3 mcg, folic acid 400 mcg, and uridine monophosphate 50 mg (Keltican) daily for 60 days reduces pain by 44% and decreases analgesic use by over 75% when compared to baseline in patients with peripheral neuropathy, including those with lumbar/lumbosacral radiculopathy, sciatic pain, and cervical radiculopathy (90384). The validity of this finding is limited by the lack of a control group. Furthermore, it is unclear if the benefits are due to vitamin B12, other ingredients, or the combination.
• Psoriasis. Topical vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that a specific cream containing vitamin B12 and avocado oil (Regividerm, Regeneratio Pharma AG) reduces symptoms of psoriasis as effectively as calcipotriol ointment (Psorcutan) after 12 weeks of therapy. The vitamin B12 combination cream also causes less irritation than calcipotriol (14909). It is unclear if the benefits are due to vitamin B12, other ingredients, or the combination.
• Respiratory tract infections. A small study suggests that oral vitamin B12 does not reduce the rate of respiratory tract infections in children. Details: Preliminary clinical research in children aged 6-30 months from low-and middle-income countries suggests that taking vitamin B12 at twice the recommended dietary allowance with or without folic acid does not reduce the risk for lower respiratory tract infections when compared with placebo (90391).
• Schizophrenia. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination of vitamin B12 400 mcg and folic acid 2 mg daily for 16 weeks improves negative symptoms when compared with placebo in patients with schizophrenia who have persistent symptoms and a specific genetic variant of the folate transporter gene FOLHI. This variant normally results in reduced folate absorption. However, in patients without this genetic variant, folate is not beneficial with respect to negative symptom improvement (90387).
• Sickle cell disease. Oral vitamin B12 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B12 4.2-6 mcg, folic acid 700 mcg, and vitamin B6 4.2-6 mg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
• Stroke. It is unclear if oral vitamin B12, either alone or with other B vitamins, is beneficial for stroke prevention. Details: Epidemiological research has found that people with a higher intake of vitamin B12 from dietary sources do not have a reduced risk of ischemic or hemorrhagic stroke (14316). A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50420,50423,83050,90379,90380,96150). However, a more recent meta-analysis of 10 clinical trials including over 44,000 patients shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk or with a history of CVD (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, a meta-analysis in adults with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and vascular death by 11% when compared with placebo (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis suggests that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Another meta-analysis suggests that exposure to low, but not high, amounts of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
• Tinnitus. It is unclear if intramuscular vitamin B12 is beneficial in patients with tinnitus. Details: A small clinical study shows that intramuscular vitamin B12 2500 mcg weekly for 6 weeks reduces tinnitus severity by 22% when compared to baseline in patients with chronic tinnitus and vitamin B12 deficiency, but not in patients with normal levels of vitamin B12. Vitamin B12 does not improve pitch or volume in either group of patients (96170). The validity of this finding is limited by the lack of a control group.
• Venous thromboembolism (VTE). It is unclear if oral vitamin B12 is beneficial for preventing VTE. Details: Epidemiological research has found that low levels of vitamin B12 are associated with an increased risk for VTE. However, clinical trials evaluating the use of B vitamins for prevention of VTE have shown conflicting results (90398). More evidence is needed to rate vitamin B12 for these uses.

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EFFECTIVE

• Pyridoxine-dependent epilepsy. Intravenous vitamin B6 is effective for controlling pyridoxine-dependent seizures. Details: Pyridoxine-dependent seizures are a rare type of refractory seizures in neonates that do not respond to anticonvulsant drugs. These seizures are typically controlled within minutes of intravenous administration of pyridoxine, a form of vitamin B6. Pyridoxine-dependent seizures can be due to genetic (autosomal recessive) pyridoxine dependency, or more commonly, a result of the use of high-dose pyridoxine during pregnancy (8197,8198).
• Sideroblastic anemia. Oral vitamin B6 is effective for treating hereditary sideroblastic anemia. Details: Taking vitamin B6 (pyridoxine) orally is effective for treating hereditary sideroblastic anemia (15,9518). Taking the active form of vitamin B6 (pyridoxal-5'-phosphate) also seems to be effective in cases in which the patient does not respond to pyridoxine (93049).
• Vitamin B6 deficiency. Oral vitamin B6 is effective for preventing and treating vitamin B6 deficiency. Details: Taking oral vitamin B6 can prevent and treat vitamin B6 deficiency (15).

LIKELY EFFECTIVE

• Hyperhomocysteinemia. Taking vitamin B6 orally, alone or in combination with folic acid, is effective for reducing hyperhomocysteinemia. Details: Vitamin B6 (pyridoxine) seems to lower homocysteine concentrations when folic acid and vitamin B12 are at physiologic levels or when given with folic acid and vitamin B12 supplements (9451,83042,107136). A combination of vitamin B6 100 mg and folic acid 0.5 mg daily seems to lower homocysteine levels by about 35% and is recommended for people with postprandial hyperhomocysteinemia (1489,9406). Other research shows that taking pyridoxine 50-200 mg daily reduces postprandial homocysteine levels by 32% to 35% (9406,10350). Pyridoxine also seems to reduce homocysteine levels in patients with kidney failure, kidney transplant patients (1489,6884,9414,9415), or patients who receive general anesthesia with nitrous oxide (9481). However, some research in healthy adults suggests that adding pyridoxine to folic acid might not provide any additional benefit over folic acid alone (9400,9405,9409,50145). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,3323,9402,9405,9408,9409). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50% and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9308,9400,9405,9409). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem to help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50423,83050,97619). There is also debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired renal function (11387,13482,50423,83050,96150). However, a more recent meta-analysis shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk for or with a history of CVD (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136).

POSSIBLY EFFECTIVE

• Antipsychotic-induced hyperprolactinemia. It is unclear if oral vitamin B6 is beneficial for patients with antipsychotic-induced hyperprolactinemia. Details: Clinical research in male patients with hyperprolactinemia who are on a consistent antipsychotic dose shows that taking vitamin B6 300 mg twice daily for 16 weeks reduces serum prolactin levels by 68%, compared with 37% in patients taking aripiprazole 5 mg twice daily. Also, 67% of patients taking vitamin B6 had prolactin levels less than 40 mcg/mL versus 2% of those taking aripiprazole (107128).
• Kidney stones (nephrolithiasis). Oral vitamin B6 seems to decrease urinary oxalate levels and decrease the risk of kidney stone formation in some patients. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally, alone or in combination with magnesium, can decrease urinary oxalate levels in people with type I primary hyperoxaluria, a hereditary disorder (1201,6437,6438,6439,6440,8548,8549,8550). Additionally, a small clinical study in this population suggests that intravenous pyridoxine hydrochloride can reduce urinary oxalate by 25.5% when compared to baseline (90796). In patients with idiopathic hyperoxaluria, taking a combination of pyridoxine 25mg and magnesium oxide 400 mg for 3 months decreases urinary oxalate by approximately 16%, with 68% of patients experiencing a reduction. However, supplementation is less effective than following a low-oxalate diet, which reduces urinary oxalate in 91% of patients by an average of 31% (107127). There is also preliminary evidence that higher pyridoxine intake in females with no history of kidney stones is associated with decreased risk of kidney stone formation (6441), but this association has not been found in males (6442).
• Pregnancy-induced nausea and vomiting. Oral vitamin B6 may reduce nausea and vomiting in some pregnant patients and is sometimes used in combination with doxylamine. Details: While some conflicting evidence exists, most small clinical studies suggest that oral vitamin B6 is effective for improving nausea and vomiting associated with pregnancy when compared with baseline or placebo. However, vitamin B6 may not be as effective as ginger (110459). Two small clinical studies show that taking vitamin B6 (pyridoxine) 25 mg every 8 hours for 3-4 days decreases pregnancy-induced nausea severity and vomiting incidence when compared with placebo (6168,16306). A larger clinical trial shows that taking lower doses of vitamin B6, 10 mg every 8 hours over 5 days, improves pregnancy-induced nausea, but not vomiting, when compared with placebo (6167). A small clinical study in patients with mild to moderate nausea and vomiting shows that taking a higher dose of 40 mg twice daily for 4 days is more effective than placebo, but no better than ginger 500 mg twice daily (99404). The American College of Obstetrics and Gynecology (ACOG) considers vitamin B6 at a dose of 10-25 mg 3 to 4 times daily a first-line treatment for pregnancy-induced nausea and vomiting due to its benign safety profile (111601). However, it is not effective for all patients, such as those with hyperemesis gravidarum, a severe form of pregnancy-induced nausea and vomiting. Adding vitamin B6 20 mg three times daily for 2 weeks to intravenous rehydration, metoclopramide, and thiamine seems to be no more effective than placebo for reducing vomiting in hyperemesis gravidarum (99405). Vitamin B6 is also sometimes used in combination with doxylamine. In fact, a combination of vitamin B6 plus doxylamine (Diclegis or Bonjesta, Duchesnay Inc., and various generics) has been approved by the US Food and Drug Administration (FDA) as a prescription product111601). ACOG recommends vitamin B6 in combination with doxylamine as another first-line treatment option (111601). However, the clinical trial used to obtain FDA approval has some methodological problems, and the significance of the results has been questioned. The improvement in symptom scores seen with Diclegis was less than one point on a 13-point scale, which is unlikely to be clinically significant (97998). Also, some clinical research shows that taking pyridoxine 25 mg and doxylamine 12.5 mg is less effective than ondansetron 4 mg when taken every 8 hours for 5 days. Only 41% of the patients using pyridoxine and doxylamine had a clinically significant reduction in nausea, compared to 92% of patients using ondansetron (90797). The combination of vitamin B6 and doxylamine is also studied with acupuncture. A large clinical study in patients with moderate to severe pregnancy-induced nausea and vomiting conducted in China shows that taking vitamin B6-doxylamine (Diclegis, Duchesnay, Inc) 20 to 40 mg each at bedtime for 14 days in combination with daily acupuncture modestly improves patient-reported nausea and vomiting scores when compared with either intervention alone (111820). However, it is unclear whether this improvement is clinically significant.
• Premenstrual syndrome (PMS). Oral vitamin B6 seems to reduce PMS symptoms. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally can improve symptoms of PMS such as breast pain or tenderness (mastalgia) and depression in some patients. Pyridoxine in doses of at least 50 mg daily, plus magnesium oxide 200 mg daily, seems to relieve PMS-related anxiety and other symptoms (8555,39007,82962). Although some clinicians advocate doses of pyridoxine 200-500 mg daily for PMS, doses of 50-100 mg daily seem to work just as well. There is no apparent dose-response curve for PMS, so the lowest effective dose should be used. Higher doses might increase the risk of side effects (3093).

POSSIBLY INEFFECTIVE

• Age-related cognitive decline. Oral vitamin B6 does not seem to slow age-related cognitive decline. Details: One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374). Furthermore, other clinical research shows that taking vitamin B6 (pyridoxine) 3-75 mg daily in combination with folic acid and vitamin B12 does not improve cognitive function in elderly adults (14392,50225,50510).
• Alzheimer disease. Oral vitamin B6 does not seem to improve cognitive function in patients with Alzheimer disease when used in combination with other B vitamins. Also, oral vitamin B6 does not seem to reduce the risk of developing this condition. Details: Clinical research in patients with probable Alzheimer disease taking routine medications shows that taking vitamin B6 25 mg with folic acid 5 mg and vitamin B12 1 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, population research in elderly adults has found that a high intake of vitamin B6 from dietary or supplemental sources is not associated with a decreased risk of Alzheimer disease when compared to lower vitamin B6 intake (13165,15270).
• Carpal tunnel syndrome. Oral vitamin B6 does not seem to reduce symptoms of carpal tunnel syndrome. Details: Most research shows that people with carpal tunnel syndrome are not generally deficient in vitamin B6 and do not benefit from taking vitamin B6 supplements (8203,8937,9448,9450,9478,9482). Although early studies by a single group of researchers, as well as anecdotal reports, suggest that taking vitamin B6 may relieve carpal tunnel symptoms, more reliable research has not supported these findings (8202,9445,9447,9449,9483,15955,83086). Vitamin B6 has also been evaluated in combination with other ingredients. A moderate-sized clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamin B6, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, turmeric, and vitamins C, E, B1, B2, and B12 twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with a control (111702). The dose of vitamin B6 was not provided. The validity of this study is limited by the lack of blinding and placebo. Additionally, it is unclear if the effects are due to vitamin B6, other ingredients, or the combination.
• Cataracts. Oral vitamin B6 does not seem to slow cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg, vitamin B6 (form not specified) 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts when compared with placebo. Furthermore, the risk of cataract extraction was increased by 28% (96149).
• Chemotherapy-induced acral erythema. While some conflicting evidence exists, most research suggests that oral or topical vitamin B6 does not seem to prevent or reduce the severity of acral erythema induced by chemotherapy. Details: A meta-analysis of 10 clinical trials and 4 observational studies shows that taking vitamin B6 60-500 mg daily for up to 8 chemotherapy cycles does not prevent chemotherapy-induced acral erythema or reduce the incidence of severe cases when compared with control. Most studies used capecitabine chemotherapy alone or in combination, and one study used pegylated liposomal doxorubicin; however, no subgroup analysis was conducted to differentiate chemotherapy regimens. Results did not seem to vary based on study location, study design, or vitamin B6 dose (104930). However, a more recent preliminary clinical study in patients receiving doxorubicin for multiple myeloma shows that taking vitamin B6 100 mg on the first day of chemotherapy then twice daily for 7 days with each cycle reduces the risk of developing acral erythema by 72%, but does not improve the severity of acral erythema, when compared with no vitamin B6 supplementation (110458). Also, one small, low-quality clinical study suggests that taking vitamin B6 400 mg daily reduces the risk of moderate or severe chemotherapy-induced acral erythema when compared with vitamin B6 200 mg daily; however, the higher dose also seems to be associated with worsened tumor response and increased treatment failure (97620). Topical vitamin B6 has also failed to show benefit. A small clinical study in patients with acral erythema from capecitabine or pegylated liposomal doxorubicin shows that applying vitamin B6 1% cream to affected areas three times daily for 6 weeks does not improve symptoms when compared with placebo (104929).
• Colorectal adenoma. Oral vitamin B6 does not seem to reduce the risk of developing colorectal adenomas. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 (pyridoxine) 50 mg, and vitamin B12 1 mg, daily for up to 9.2 years does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389).
• Eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of eclampsia when compared with control (83046,96166).
• Osteoporosis. Oral vitamin B6 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in patients with cerebrovascular disease shows that taking a combination of B vitamins, including folic acid 2 mg, vitamin B6 (form not specified) 25 mg, and vitamin B12 500 mcg daily for up to 10.5 years does not prevent osteoporotic fractures when compared with placebo (90377). Furthermore, a secondary analysis of two large studies in patients with cardiovascular disease has found that taking vitamin B6 (pyridoxine) 40 mg daily in addition to folic acid and vitamin B12 for 1-3 years is associated with a 42% increased risk of hip fracture over an 11-year period when compared with only folic acid and vitamin B12 (96163). This finding is limited because these studies were not designed to assess the effects of vitamin B6 on fracture risk and the analyses were not adjusted for baseline bone health or fall risk.
• Pre-eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of pre-eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of pre-eclampsia when compared with placebo (83046,96166).
• Preterm labor. Oral or intramuscular vitamin B6 does not seem to reduce the risk of preterm labor. Details: Meta-analyses of limited clinical research in pregnant patients shows that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of preterm labor when compared with placebo (83046,96166).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acne. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing vitamin B6 (pyridoxine), nicotinamide, azelaic acid, zinc, copper, and folic acid for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared to baseline (90800). The validity of these findings is limited by the lack of a comparator group.
• Age-related macular degeneration (AMD). Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B6 (pyridoxine) 50 mg, vitamin B12 1000 mcg, and folic acid 2.5 mg daily reduces the risk for AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
• Angioplasty. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B6 (pyridoxine) 10 mg, folic acid 1 mg, and vitamin B12 400 mcg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6 (pyridoxine), and vitamin B12 followed by oral administration of folic acid 1.2 mcg, vitamin B6 (pyridoxine) 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B6, other ingredients, or the combination.
• Antipsychotic-induced metabolic side effects. It is unclear if oral vitamin B6, as an adjunct to progesterone, is beneficial in patients with antipsychotic-induced amenorrhea. Details: A small clinical study in females with antipsychotic-induced amenorrhea shows that taking vitamin B6 80 mg three times daily for 1 month plus intramuscular progesterone daily for 5 days increases levels of estradiol and follicle stimulating hormone, reduces prolactin levels, and increases the rate of clinical efficacy, defined as the normalization of menstruation and improvement in endocrine indicators, by 14% when compared with progesterone alone (110457).
• Anxiety. It is unclear if oral vitamin B6 is beneficial in patients with anxiety. Details: Clinical research in college students shows that taking vitamin B6 100 mg daily for one month does not reduce anxiety scores when compared with placebo (110453). However, because a diagnosis of anxiety was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with anxiety.
• Asthma. It is unclear if oral vitamin B6 is beneficial in patients with asthma. Details: Preliminary clinical studies show that taking vitamin B6 (pyridoxine) 200-300 mg daily may improve symptoms of asthma in some patients, but not others, when compared with placebo (7064,7065). Studies have yielded conflicting results, with some research suggesting that it may only be beneficial in children with severe asthma (7065). Additionally, some research suggests that theophylline may lower vitamin B6 levels, although it is unclear if vitamin B6 supplementation is beneficial (4522,7066,9503).
• Atherosclerosis. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with intermediate risk for coronary heart disease shows that taking a specific supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing vitamin B6 12.5 mg, aged garlic extract 250 mg, vitamin B12 100 mcg, folic acid 300 mcg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
• Atopic dermatitis (eczema). It is unclear if oral vitamin B6 is beneficial in patients with eczema. Details: A small clinical study in children with eczema shows that taking vitamin B6 (pyridoxine hydrochloride) 50 mg daily for 4 weeks does not reduce symptoms such as redness and itchiness when compared with placebo (83090).
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral vitamin B6 is beneficial for ADHD. Details: A small crossover study in children with ADHD shows that taking vitamin B6 600 mg, niacinamide and ascorbic acid 3 grams, and calcium pantothenate 1.2 grams daily for 6 weeks does not improve behavior scores when compared with placebo (9957).
• Autism spectrum disorder. Although there is interest in using oral vitamin B6 for autism, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Bipolar disorder. It is unclear if oral vitamin B6 is beneficial in patients with bipolar disorder. Details: A small clinical trial in patients with type 1 bipolar disorder who are taking lithium and experiencing an acute episode of mania shows that taking vitamin B6 80 mg daily for 8 weeks does not improve cognitive function or the severity of mania when compared with placebo. Cognitive function was reduced in patients taking vitamin B6; any effect on sleep was unclear (107132).
• Cancer. It is unclear if oral vitamin B6 reduces overall cancer risk. Details: Population research has found that higher dietary intake of vitamin B6 is associated with a 22% reduced risk of cancer, including esophageal, pancreatic, gastric, colorectal, and breast cancer. However, when dietary and supplemental vitamin B6 intake is considered, the inverse association between vitamin B6 and cancer risk is weaker and limited to fewer tumor sites. Furthermore, a meta-analysis of 9 clinical studies shows that taking vitamin B6 3-100 mg orally daily for 2-7.3 years, in combination with vitamin B12 and folate, does not reduce the risk of cancer in patients with cardiovascular disease or kidney failure (96164).
• Cardiovascular disease (CVD). Oral vitamin B6, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly lower the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B6 in combination with folic acid and/or vitamin B12 does not seem to help with secondary prevention of death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, some research shows that taking vitamin B6 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). Additionally, it is unclear which specific combination of B vitamins is optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
• Cognitive function. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy adults aged 40-65 years shows that taking a supplement containing vitamin B6, ginkgo leaf, bacopa, and other B vitamins twice daily for 12 weeks does not improve memory or attention when compared with placebo (111334).
• Colorectal cancer. It is unclear if oral vitamin B6 reduces the risk of colorectal cancer. Details: A meta-analysis of observational studies suggests that the highest dietary intake of vitamin B6 is associated with a 20% reduced risk of colorectal cancer when compared with the lowest dietary intake. However, this association was not shown in subgroup analyses of studies conducted in Australia, Europe, or North America (111600). The validity of this analysis is limited by the heterogeneity of the included studies.
• Dental caries. There is limited evidence on the oral use of vitamin B6 for dental decay during pregnancy. Details: Meta-analyses of limited clinical research show that taking vitamin B6 (pyridoxine), 25 mg daily or a single dose of 100 mg orally or intramuscularly, may reduce the risk of dental decay during pregnancy when compared with placebo (83046,96166).
• Depression. It is unclear if oral vitamin B6 reduces the risk of developing depression or improves symptoms of depression. Details: Clinical research in healthy college students shows that taking vitamin B6 100 mg daily for one month does not reduce depression scores when compared with placebo (1104453). However, because a diagnosis of depression was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with depression. Whether vitamin B6 reduces the risk of developing depression is also unclear. A meta-analysis of population research has found that the highest dietary intake of vitamin B6 is associated with a 19% lower risk of depression when compared with the lowest intake. However, sub-analyses suggest that this association is only relevant in females and not males (107133). In one individual population study in community dwelling older adults included in the analysis, the consumption of at least 1.71 mg of vitamin B6 daily from food was associated with a 43% reduction in the likelihood of becoming depressed when compared with the consumption of 1.33 mg or less daily in females. However, there was no association between vitamin B6 levels and risk of depression in males, and the finding in females was no longer significant when adjusted for total energy intake, since foods rich in vitamin B6 are energy-dense (96168). Another observational longitudinal study in healthy adults starting oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 40% lower risk of depression when compared with no supplementation (90789). Most available studies are cross-sectional in nature, making any conclusions related to causation difficult.
• Diabetes. It is unclear if oral vitamin B6 is beneficial in patients with type 2 diabetes or gestational diabetes. Details: Observational research in Chinese adults with type 2 diabetes has found that dietary intake of vitamin B6 in the highest quartile is associated with 53% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with vitamin B6 intake in the lowest quartile (110452). Small clinical studies in patients with gestational diabetes and vitamin B6 deficiency shows that taking vitamin B6 (pyridoxine) 100 mg daily for 2 weeks improves glucose tolerance and blood glucose levels when compared with baseline (82967,83088). However, there is concern that these findings were confounded by dietary alterations. This benefit was not observed in a subsequent small case series in patients with gestational diabetes (22380).
• Diabetic neuropathy. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research suggests that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate) for 24 weeks does not improve neural dysfunction based on vibration perception when compared with placebo in patients with diabetic neuropathy. However, taking this combination appears to modestly improve neuropathy symptoms and quality of life related to mental functioning when compared with placebo (90375).
• Dysmenorrhea. It is unclear if oral vitamin B6 is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research shows that taking vitamin B6 (form not specified) 200 mg daily reduces pain associated with dysmenorrhea when compared with placebo. However, taking vitamin B6 in combination with magnesium does not reduce pain when compared with placebo (77388).
• Fibromyalgia. It is unclear if oral vitamin B6 is beneficial in patients with fibromyalgia. Details: A small clinical study in patients with fibromyalgia shows that taking vitamin B6 80 mg daily for 8 weeks does not improve pain, disease severity, anxiety, depression, or quality of life when compared with placebo (110454).
• Gastroenteritis-associated nausea and vomiting. It is unclear if oral vitamin B6 is beneficial in children with gastroenteritis. Details: A small clinical study in children aged 6 months to 12 years with acute viral gastroenteritis shows that taking vitamin B6 (form not specified) does not improve symptoms of dehydration or the frequency of vomiting when compared with placebo (90793).
• Helicobacter pylori. It is unclear if oral vitamin B6 is beneficial for Helicobacter pylori. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy does not improve eradication rates when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding.
• Hypertension. It is unclear if oral vitamin B6 reduces blood pressure. Details: One small clinical study in patients with essential hypertension shows that taking vitamin B6 (pyridoxine hydrochloride) 5 mg/kg daily for 4 weeks can reduce systolic and diastolic blood pressure when compared with baseline (83091). The validity of this finding is limited by the lack of a control group.
• Hypertriglyceridemia. It is unclear if oral vitamin B6 reduces triglyceride levels. Details: Preliminary clinical research shows that vitamin B6 (form not specified) 50 mg daily for 12 weeks does not reduce triglyceride levels in people with hypertriglyceridemia when compared with placebo. However, vitamin B6 appears to decrease total cholesterol and high-density lipoprotein (HDL) cholesterol by approximately 9% in these patients (59028).
• Infertility. Although there is interest in using oral vitamin B6 for infertility, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Insomnia. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in healthy adults with self-reported sleep difficulty shows that taking a specific product (LZ Complex3, Sanofi Consumer Healthcare Pty Ltd.) containing vitamin B6, zizyphus extract, hops extract, hydrolyzed milk protein (Lactium), and magnesium oxide nightly, 30 minutes before bed, for 2 weeks does not improve sleep quality, daytime functioning, or physical fatigue when compared with placebo. However, due to the large improvement seen in both the treatment and placebo groups, the effectiveness of this product is unclear (95971).
• Isoniazid-induced neuropathy. It is unclear if oral vitamin B6 prevents the development of neuropathy in patients taking isoniazid. Details: Preliminary clinical research in patients taking isoniazid for tuberculosis shows that taking vitamin B6 (pyridoxine) 6 mg daily reduces the development of neuropathy when compared with control (83068).
• Lactation. It is unclear if oral vitamin B6 helps to suppress postpartum lactation. Details: A meta-analysis of two small clinical trials shows that taking vitamin B6 (pyridoxine) 400-600 mg daily for 6-7 days postpartum does not suppress lactation when compared with no treatment (83047).
• Levetiracetam-induced side effects. While some conflicting evidence exists, several small, low-quality studies suggest that oral vitamin B6 (pyridoxine) may reduce some neuropsychiatric adverse effects related to the use of levetiracetam. Details: In an analysis of case reports, retrospective studies, and a single low-quality prospective study, improvement in levetiracetam-associated neuropsychiatric symptoms occurred in approximately 73% of patients taking pyridoxine (107137). A more recent preliminary clinical trial in children ages 1-17 years shows that taking pyridoxine 10 or 15 mg/kg daily as needed based on symptoms improves behavioral side effects associated with levetiracetam by a small amount when compared with low-dose pyridoxine 0.5 mg/kg daily used as placebo (107124). Also, observational research in children ages 9 months to 14 years has found that taking vitamin B6 is associated with improved behavior and a 44% lower risk of levetiracetam discontinuation when compared with no vitamin B6 supplementation (110455). Some observational research in adults with levetiracetam-associated irritability has found that taking vitamin B6 is associated with an improvement in irritability in 45% of patients when compared to baseline (107129). However, a small clinical trial in adults with epilepsy shows that taking pyridoxine 40 mg daily for 3 weeks does not improve levetiracetam-related psychiatric adverse effects when compared with placebo (110456). This study may have been underpowered to detect differences between groups. Pyridoxine doses used in the studies above have ranged from 50-400 mg daily in children and 40-600 mg daily in adults (107124,107129,107137,110456).
• Lung cancer. It is unclear if dietary or oral vitamin B6 reduces lung cancer risk. Details: Epidemiological research has found that higher serum levels of vitamin B6 in male smokers is associated with a lower risk of lung cancer (9454). Also, people with blood levels of vitamin B6 in the top quartile have a modestly lower risk of lung cancer when compared with those whose levels are in the lowest quartile. The association is stronger for males and for people who have smoked (97999). However, other epidemiological research found that increased dietary intake of vitamin B6 is not associated with a reduced risk of lung cancer (96164).
• Menopausal symptoms. Although there is interest in using oral vitamin B6 for menopausal symptoms, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Motion sickness. Although there is interest in using oral vitamin B6 for motion sickness, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
• Nausea and vomiting. It is unclear if oral vitamin B6 is beneficial for nausea and vomiting in patients taking oral contraceptives or antibiotics for Helicobacter pylori. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy reduces the incidence and severity of gastrointestinal adverse effects when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding. An observational longitudinal study in healthy females taking oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 43% reduced risk of nausea when compared with no supplementation (90789).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B6 for patients with NAFLD. Details: A small clinical trial in patients with NAFLD shows that taking vitamin B6 (pyridoxine) 30 mg three times daily for 12 weeks does not reduce levels of liver transaminases or plasma lipids when compared with baseline. However, hepatic fat accumulation was modestly reduced (107130). The validity of this study is limited by the lack of a comparator group.
• Obesity. It is unclear if oral vitamin B6 in beneficial in overweight or obese individuals. Details: A small clinical trial in females with a body mass index (BMI) of at least 25 kg/m² shows that taking vitamin B6 as pyridoxine 80 mg daily for 8 weeks reduces fat mass and improves insulin resistance and triglyceride levels by a small amount when compared with placebo. Although some other anthropometric and metabolic indices were improved when compared with baseline, there was no effect of pyridoxine on body weight, visceral adiposity, or other endpoints when compared with placebo (107131).
• Overall mortality. It is unclear if oral vitamin B6 reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of vitamin B6 in the highest quintile is associated with a 12% to 21% lower risk of all-cause mortality and a 31% to 44% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary vitamin B6 intake (110451).
• Pancreatic cancer. It is unclear if oral vitamin B6 reduces the risk of pancreatic cancer. Details: Observational research has found that higher dietary intake of vitamin B6 is associated with a 37% lower risk of developing pancreatic cancer when compared with lower intake (104927).
• Postpartum depression. It is unclear if oral vitamin B6 is beneficial in patients with postpartum depression. Details: Preliminary clinical research in individuals considered at increased risk for postpartum depression, but without clinical depression, shows that taking vitamin B6 80 mg daily from the 28th week of pregnancy until birth, and then 40 mg daily for one month, reduces symptoms of depression 1.5 months after birth when compared with baseline (measured during the third trimester) and when compared with placebo. However, it is unclear if any of the patients included in the study developed postpartum depression, as there were no changes in overall symptoms in patients taking placebo (107126).
• Proton pump inhibitor-induced gastrointestinal (GI) symptoms. It is unclear if oral vitamin B6 is beneficial for proton pump inhibitor-induced GI symptoms. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy reduces the incidence and severity of gastrointestinal adverse effects when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding.
• Restless legs syndrome (RLS). It is unclear if oral vitamin B6 is beneficial in patients with RLS. Details: A small clinical study in adults with RLS who are beginning treatment with pramipexole shows that also taking vitamin B6 40 mg daily for 2 months moderately improves RLS scores and sleep quality scores when compared with pramipexole and placebo (110052).
• Schizophrenia. It is unclear if oral vitamin B6 is beneficial for patients with treatment-resistant schizophrenia. Details: Clinical research in male patients with treatment-resistant schizophrenia who are on a consistent antipsychotic dose shows that adding vitamin B6 300 mg twice daily for 16 weeks modestly improves psychotic symptoms and some measures of cognitive performance when compared with adding aripiprazole 5 mg twice daily (107128). More research is needed to determine if these benefits are clinically relevant.
• Seizures. It is unclear if oral vitamin B6 is beneficial for preventing seizures in patients with glycosylphosphatidylinositol (GPI) deficiency. Details: Observational case series in a small number of children and young adults with GPI deficiency has found that taking vitamin B6 20-30 mg/kg daily for 3-12 months is associated with some reduction in seizure frequency in 9 of 13 patients. However, no patient reached seizure freedom (107125,107135). In one case series, treatment for 12 months was associated with modest developmental improvements in almost all patients (107135). The study patient populations were slightly different in terms of age and underlying genetic causes for GPI deficiency.
• Sickle cell disease. Oral vitamin B6 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B6 4.2-6 mg, vitamin B12 4.2-6 mcg, and folic acid 700 mcg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
• Stroke. It is unclear if oral vitamin B6, either alone or with other B vitamins, is beneficial for stroke prevention. Details: There is some debate about whether supplementation with homocysteine-lowering B vitamins, including vitamin B6, can reduce the risk of stroke. A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, another meta-analysis of three clinical trials including 9900 patients with a history of stroke shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% when compared with placebo, although this finding was determined to have a low level of certainty. Based on two clinical trials, there was also a 17% reduced risk of vascular death and an 11% reduction in the combined risk of stroke, myocardial infarction, and vascular death (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis shows that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Exposure to low, but not high amounts, of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
• Tardive dyskinesia. It is unclear if oral vitamin B6 prevents tardive dyskinesia in patients taking neuroleptic drugs. Details: A small clinical study in patients taking neuroleptic drugs for schizophrenia shows that taking vitamin B6 (form not specified) 400 mg daily seems to improve Parkinsonian, dystonic, and dyskinetic symptoms when compared with placebo (8558).
• Tourette syndrome. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, nonblinded clinical study in children aged 4-17 years with untreated Tourette syndrome or with chronic tic disorder and associated symptoms of anxiety shows that taking a liquid nutritional supplement providing vitamin B6 2.8 mg and L-theanine 200 mg daily for 2 months improves scores on the Yale Global Tic Severity Scale, but does not reduce anxiety, when compared with patients receiving psychoeducation (108555). This study may have been inadequately powered to detect a difference between groups.
• Vincristine-induced neuropathy. Oral vitamin B6 has only been evaluated in combination with pyridostigmine; its effect when used alone is unclear. Details: A small clinical study in children ages 11 months to 13 years with neuropathy due to vincristine treatment for acute lymphoblastic leukemia, shows that taking vitamin B6 150 mg/m2 and pyridostigmine 3 mg/kg twice daily for 3 months is associated with reduced severity of sensory and motor neuropathy when compared with baseline (104928). The validity of this finding is limited by the lack of a control group. More evidence is needed to rate vitamin B6 for these uses.

(Read more about VITAMIN B6)

POSSIBLY SAFE ...when used orally and appropriately, short-term. Oral beta-alanine, including a specific commercial product (CarnoSyn, Natural Alternatives International), has been used with apparent safety in doses up to 6.4 grams daily for 12 weeks in younger adults (14611,16025,16439,16441,18227,94357,97972,101028,101029,104144,106717), and up to 3.2 grams daily for 12 weeks in adults aged 55 years and older (16442,97955,97961,97965).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using in medicinal amounts.

(Read more about BETA-ALANINE)

LIKELY SAFE ...when used orally, parenterally, or rectally and appropriately. Caffeine has Generally Recognized As Safe (GRAS) status in the US (4912,98806). Caffeine is also an FDA-approved product and a component of several over-the-counter and prescription products (4912,11832). According to a review by Health Canada, and a subsequent large meta-analysis conducted in the US, doses of caffeine up to 400 mg daily are not associated with significant adverse cardiovascular, bone, behavioral, or reproductive effects in healthy adults (11733,98806). The US Dietary Guidelines Advisory Committee states that there is strong and consistent evidence that consumption of caffeine 400 mg daily is not associated with increased risk of major chronic diseases, such as cardiovascular disease or cancer, in healthy adults (98806). This amount of caffeine is similar to the amount of caffeine found in approximately 4 cups of coffee. Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine from caffeine-containing natural ingredients such as coffee or green tea does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product.

POSSIBLY UNSAFE ...when used orally, long-term or in high doses (91063). Chronic use, especially in large amounts, can produce tolerance, habituation, psychological dependence, and other adverse effects (3719). Acute use of high doses, typically above 400 mg daily, has been associated with significant adverse effects such as tachyarrhythmia and sleep disturbances (11832). Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine from caffeine-containing natural ingredients such as coffee or green tea does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product.

LIKELY UNSAFE ...when used orally in very high doses. The fatal acute oral dose of caffeine is estimated to be 10-14 grams (150-200 mg/kg). Serious toxicity can occur at lower doses depending on variables in caffeine sensitivity such as smoking, age, or prior caffeine use (11832,95700,97454,104573). Caffeine products sold to consumers in highly concentrated or pure formulations are considered to a serious health concern because these products have a risk of being used in very high doses. Concentrated liquid caffeine can contain about 2 grams of caffeine in a half cup. Powdered pure caffeine can contain about 3.2 grams of caffeine in one teaspoon. Powdered pure caffeine can be fatal in adults when used in doses of 2 tablespoons or less. As of 2018, these products are considered by the FDA to be unlawful when sold to consumers in bulk quantities (95700).

CHILDREN: POSSIBLY SAFE
when used orally or intravenously and appropriately in neonates under the guidance of a healthcare professional (6371,38340,38344,91084,91087,97452). ...when used orally in amounts commonly found in foods and beverages in children and adolescents (4912,11833,36555). Daily intake of caffeine in doses of less than 2.5 mg/kg daily are not associated with significant adverse effects in children and adolescents (11733,98806). Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine from caffeine-containing natural ingredients such as coffee or green tea does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product.

PREGNANCY: POSSIBLY SAFE
when used orally in amounts commonly found in foods. Intakes of caffeine should be monitored during pregnancy. Caffeine crosses the human placenta, but is not considered a teratogen (38048,38252,91032). Fetal blood and tissue levels are similar to maternal concentrations (4260). The use of caffeine during pregnancy is controversial; however, moderate consumption has not been associated with clinically important adverse fetal effects (2708,2709,2710,2711,9606,16014,16015,98806,108814). In some studies consuming amounts over 200 mg daily is associated with a significantly increased risk of miscarriage (16014,37960). This increased risk seems to occur in those with genotypes that confer a slow rate of caffeine metabolism (98806). According to a review by Health Canada, and a subsequent large meta-analysis conducted in the US, up to 300 mg daily can be consumed during pregnancy without an increased risk of spontaneous abortion, stillbirth, preterm birth, fetal growth retardation, or congenital malformations (11733,98806). However, observational research in a Norwegian cohort found that caffeine consumption is associated with a 16% increased odds of the baby being born small for gestational age when compared with no consumption (100369,103707). The same Norwegian cohort found that low to moderate caffeine consumption during pregnancy is not associated with changes in neurodevelopment in children up to 8 years of age (103699). Advise patients to keep caffeine consumption below 300 mg daily during pregnancy. This is similar to the amount of caffeine in about 3 cups of coffee or tea.

PREGNANCY: POSSIBLY UNSAFE
when used orally in amounts over 300 mg daily. Caffeine crosses the placenta, producing fetal blood concentrations similar to maternal levels (4260,98806). Consumption of caffeine in amounts over 300 mg daily is associated with a significantly increased risk of miscarriage in some studies (16014,98806). Advise patients to keep caffeine consumption below 300 mg daily during pregnancy. This is similar to the amount of caffeine in about 3 cups of coffee or tea. Additionally, high doses of caffeine throughout pregnancy have resulted in symptoms of caffeine withdrawal in newborn infants (9891). High doses of caffeine have also been associated with spontaneous abortion, premature delivery, and low birth weight (2709,2711,91033,91048,95949). In a cohort of mother/infant pairs with a median maternal plasma caffeine level of 168.5 ng/mL (range 29.5-650.5 ng/mL) during pregnancy, birth weights and lengths were lower in the 4th quartile of caffeine intake compared with the 1st. By age 7, heights and weights were lower by 1.5 cm and 1.1 kg respectively. In another cohort of mother/infant pairs with higher maternal pregnancy plasma caffeine levels, median 625.5 ng/mL (range 86.2 to 1994.7 ng/mL), heights at age 8 were 2.2 cm lower, but there was no difference in weights (109846).

LACTATION: POSSIBLY SAFE
when used orally in amounts commonly found in foods. Caffeine intake should be closely monitored while breast-feeding. During lactation, breast milk concentrations of caffeine are thought to be approximately 50% of serum concentrations and caffeine peaks in breastmilk approximately 1-2 hours after consumption (23590).

LACTATION: POSSIBLY UNSAFE
when used orally in large amounts. Caffeine is excreted slowly in infants and may accumulate. Caffeine can cause sleep disturbances, irritability, and increased bowel activity in breast-fed infants exposed to caffeine (2708,6026).

(Read more about CAFFEINE)

LIKELY SAFE ...when used orally or intravenously and appropriately. Calcium is safe when used in appropriate doses (7555,12928,12946,95817). However, excessive doses should be avoided. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stone, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Other clinical studies suggest that, when combined with vitamin D supplementation, calcium supplementation is not associated with an increased risk of CVD, CHD, or MI (93533,107231). Other analyses report conflicting results and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients not to consume more than the recommended daily intake of 1000-1200 mg per day, to consider total calcium intake from both dietary and supplemental sources (17484), and to combine calcium supplementation with vitamin D supplementation (93533).

POSSIBLY UNSAFE ...when used orally in excessive doses. The National Academy of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 19-50 years, 2500 mg; 51 years and older, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Other clinical studies suggest that, when combined with vitamin D supplementation, calcium supplementation is not associated with an increased risk of CVD, CHD, or MI (93533,107231). Other analyses report conflicting results and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients to not consume more than the recommended daily intake of 1000-1200 mg per day, to consider total calcium intake from both dietary and supplemental sources (17484), and to combine calcium supplementation with vitamin D supplementation (93533).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Calcium is safe when used in appropriate doses (17506).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (945,1586,3263,3264,17506). The World Health Organization (WHO) recommends prescribing oral calcium supplementation 1.5-2 grams daily during pregnancy to those with low dietary calcium intake to prevent pre-eclampsia (97347).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the same daily tolerable upper intake level (UL) for calcium according to age independent of pregnancy status: 9-18 years, 3000 mg; 19-50 years, 2500 mg (17506). Doses over these amounts might increase the risk of neonatal hypocalcemia-induced seizures possibly caused by transient neonatal hypoparathyroidism in the setting of excessive calcium supplementation during pregnancy, especially during the third trimester. Neonatal hypocalcemia is a risk factor for neonatal seizures (97345).

(Read more about CALCIUM)

LIKELY SAFE ...when used orally and appropriately, short-term. Creatine supplementation appears to be safe when used at loading doses of up to 25 grams daily or 0.3 grams/kg daily for up to 14 days in healthy adults (1367,2100,2101,3996,4569,10064,15354,15520,46570,46587)(46673,46688,46719,46753,46801,103278,103279,108336). Creatine supplementation also appears to be safe when used at maintenance doses of 4-5 grams daily for up to 18 months (2101,4578,15353,15354,15520,46587,46673,46690,46753,46838,102164,103278,108336).

POSSIBLY SAFE ...when used orally and appropriately, long-term. Creatine supplementation has been safely used at doses of up to 10 grams daily for up to 5 years in some preliminary clinical research (1367,3996). There is insufficient reliable information available about the safety of creatine when used topically.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately. Creatine supplementation appears to be safe when used in appropriate doses in infants and children. Creatine 3-5 grams daily for 2-6 months has been safely used in children 5-18 years of age (6182,46596,46739,46841). Creatine 2 grams daily for 6 months has been safely used in children 2-5 years of age (46841). Additionally, weight-based dosing of creatine 0.1-0.4 grams/kg daily in infants and children or 4.69 grams/m2 in children weighing over 40 kg has been used safely for up to 6 months (46623,46629,46694,46759,104672).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about CREATINE)

LIKELY SAFE ...when used orally or parenterally and appropriately. Folic acid has been safely used in amounts below the tolerable upper intake level (UL). The UL for folic acid is based only on supplemental folic acid and is expressed in mcg folic acid. Dietary folate is not included in UL calculations, as dietary folate consumption has not been associated with adverse effects. The UL for folic acid in adults is 1000 mcg (6241). In cases of megaloblastic anemia resulting from folate deficiency or malabsorption disorders such as sprue, oral doses of 1-5 mg per day can also be used safely until hematologic recovery is documented, as long as vitamin B12 levels are routinely measured (6241,7725,8739).

POSSIBLY SAFE ...when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately, short-term. L-5-MTHF has been used with apparent safety at a dose of 416 mcg daily for 16 weeks (104913,104914) and a dose of 113 mcg daily for 24 weeks (104920). A specific L-5-MTHF product (Metafolin, Eprova) has been used with apparent safety at a dose of 1.3 mg daily for 12 weeks (104912).

POSSIBLY UNSAFE ...when used orally in large doses, long-term. Clinical research shows that taking folic acid daily in doses of 800 mcg to 1200 mcg for 3-10 years significantly increases the risk of developing cancer and adverse cardiovascular effects compared to placebo (12150,13482,16822,17041). Doses above 1 mg per day should also be avoided if possible to prevent precipitation or exacerbation of neuropathy related to vitamin B12 deficiency (6241,6242,6245). However, there is contradictory evidence suggesting that higher doses may not be harmful. There is some evidence that doses of 5 mg per day orally for up to 4 months can be used safely if vitamin B12 levels are routinely measured (7725). Also, other clinical research suggests that folic acid supplementation at doses up to 5 mg, usually in combination with vitamin B12, does not increase the risk of cancer when taken for 2-7 years (91312). Very high doses of 15 mg per day can cause significant central nervous system (CNS) and gastrointestinal side effects (505).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Folic acid has been safely used in children in amounts below the tolerable upper intake level (UL). The ULs for folic acid are based only on supplemental folic acid and are expressed in mcg folic acid. Dietary folate is not included in UL calculations, as dietary folate consumption has not been associated with adverse effects. The UL for children is: 1-3 years of age, 300 mcg; 4-8 years of age, 400 mcg; 9-13 years of age, 600 mcg; 14-18 years of age, 800 mcg (6241).

CHILDREN: POSSIBLY SAFE
when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately. One clinical study in infants aged 27 days and younger shows that consuming a formula containing L-5-MTHF (Metafolin, Merck & Cie) 10.4 mcg/100 mL daily has been used with apparent safety for up to 12 weeks (104918).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Folic acid 300-400 mcg is commonly used during pregnancy for prevention of neural tube defects (8739). Miscarriage rates and negative impacts on fetal growth have not been shown to increase with peri-conception supplemental folic acid intakes of 4 mg per day (91320,91322). However, other research shows that taking more than 5 mg per day during pregnancy may reduce development of cognitive, emotional, and motor skills in infants (91318). Also, the tolerable upper intake level (UL) of folic acid for pregnant or lactating women is 800 mcg daily for those 14-18 years of age and 1000 mcg daily for those 19 years and older (6241).

PREGNANCY AND LACTATION: POSSIBLY SAFE
when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately, short-term. L-5-MTHF has been used with apparent safety at a dose of 416 mcg daily for 16 weeks during lactation. Compared to folic acid, this form seems to further increase the folate concentration of red blood cells, but not breast milk (104913,104914).

(Read more about FOLIC ACID)

POSSIBLY SAFE ...when used orally and appropriately. L-arginine has been used safely in clinical studies at doses of up to 24 grams daily for up to 18 months (3331,3460,3595,3596,5531,5532,5533,6028,7815,7816)(8014,8473,13709,31943,91195,91196,91963,99264,99267,110380)(110387). A tolerable upper intake level (UL) for arginine has not been established, but the observed safe level (OSL) of arginine intake established in clinical research is 20 grams (31996). ...when used intravenously and appropriately. Parenteral L-arginine is an FDA-approved prescription product (15). ...when used topically and appropriately. L-arginine appears to be safe when 5 grams is applied as a topical cream twice daily for 2 weeks or when a dentifrice is used at a dose of 1.5% w/w for up to 2 years (14913,96806). ...when inhaled, short-term. L-arginine appears to be safe when inhaled twice daily at a dose of 500 mg for up to 2 weeks (96807).

CHILDREN: POSSIBLY SAFE
when used orally in premature infants and children (8474,32286,96803,97392,110391). ...when used intravenously and appropriately (97392). Parenteral L-arginine is an FDA-approved prescription product (15). ...when used topically, short-term. A dentifrice containing L-arginine appears to be safe when used at a dose of 1.5% w/w for up to 2 years in children at least 3.7 years of age (96806). ...when inhaled, short-term. L-arginine appears to be safe when inhaled twice daily at a dose of 500 mg for up to 2 weeks in children at least 13 years of age (96807).

CHILDREN: POSSIBLY UNSAFE
when used intravenously in high doses. Parenteral L-arginine is an FDA-approved prescription product (15). However, when higher than recommended doses are used, injection site reactions, hypersensitivity reactions, hematuria, and death have occurred in children (16817).

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately, short-term. L-arginine 12 grams daily for 2 days has been used with apparent safety in pregnancy during the third trimester (11828). L-arginine 3 grams daily has been taken safely during the second and/or third trimesters (31938,110379,110382). ...when used intravenously and appropriately, short-term. Intravenous L-arginine 20-30 grams daily has been used safely in pregnancy for up to 5 days (31847,31933,31961,31978).

LACTATION:
Insufficient reliable information available; avoid using.

(Read more about L-ARGININE)

POSSIBLY SAFE ...when used orally and appropriately. In clinical trials, L-citrulline has been used with apparent safety for up to 2 months at doses of 1.5-6 grams daily (94954,94956,94961,94962,100974). Doses of up to 15 grams have also been used as single doses or within a 24 hour period (16470,16473).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately. L-citrulline has been used with apparent safety in infants at a dose of 0.17 grams/kg daily (16472). It has also been used in children 6.5-10 years of age at a dose of 7.5 grams daily for 26 weeks (100976). ...when used intravenously and appropriately. An intravenous bolus dose of L-citrulline 150 mg/kg followed by 9 mg/kg/hour for 48 hours has been used safely in children under 6 years of age (16469).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about L-CITRULLINE)

LIKELY SAFE ...when niacin is taken in food or as a supplement in amounts below the tolerable upper intake level (UL) of 30 mg daily for adults 18 years of age and 35 mg daily for adults 19 years and older (6243). ...when prescription products are used orally and appropriately in doses of up to 2 grams daily (12033). CHILDREN:

LIKELY SAFE ...when used orally in amounts that do not exceed the tolerable upper intake level (UL). The ULs of niacin for children are: 1-3 years of age, 10 mg daily; 4-8 years of age, 15 mg daily; 9-13 years of age, 20 mg daily; 14-18 years of age, 30 mg daily (6243).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the tolerable upper intake level (UL). The UL of niacin during pregnancy and lactation is 30 mg daily for 14-18 years of age and 35 mg daily for 19 years and older (6243). There is insufficient reliable information available about the safety of larger oral doses of niacin during pregnancy or lactation; avoid using.

(Read more about NIACIN)

LIKELY SAFE ...when used in amounts found in foods. Typical daily intakes for adults range from 40-400 mg (101471).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts. Taurine 2-4 grams daily in two or three divided doses has been used safely in studies lasting up to 3 months (5248,5271,8217,8221,10454,77147,95612,98337,104165,104167). Higher doses of taurine 6 grams daily have been used safely in studies lasting up to 4 weeks (98336,98337). A risk assessment of orally administered taurine has identified an Observed Safe Level (OSL) of up to 3 grams daily for healthy adults (31996).

CHILDREN: LIKELY SAFE
when used in amounts found in foods.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in medicinal amounts. Taurine 2.4-4.8 grams daily in three divided doses has been safely used in children 6-16 years of age for up to 12 weeks (103210).

PREGNANCY AND LACTATION: LIKELY SAFE
when used in amounts found in foods. There is insufficient reliable information available about the safety of taurine when used in medicinal amounts during pregnancy and lactation; avoid using.

(Read more about TAURINE)

LIKELY SAFE ...when used orally in amounts commonly found in foods. Tyrosine has Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts, short-term. Tyrosine has been used safely in doses up to 150 mg/kg daily for up to 3 months (7210,7211,7215). ...when used topically and appropriately (6155).

PREGNANCY AND LACTATION:
There is insufficient reliable information available about the safety of tyrosine during pregnancy and lactation when used in medicinal amounts. Some pharmacokinetic research shows that taking a single dose of tyrosine 2-10 grams orally can modestly increase levels of free tyrosine in breast milk. However, total levels are not affected, and levels remain within the range found in infant formulas. Therefore, it is not clear if the increase in free tyrosine is a concern (91467).

(Read more about TYROSINE)

LIKELY SAFE ...when used orally, topically, intravenously, intramuscularly, or intranasally and appropriately. Vitamin B12 is generally considered safe, even in large doses (15,1344,1345,1346,1347,1348,2909,6243,7289,7881)(9414,9416,10126,14392,15765,82832,82949,82860,82864,90386)(111334,111551).

PREGNANCY: LIKELY SAFE
when used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA for vitamin B12 during pregnancy is 2.6 mcg daily (6243). There is insufficient reliable information available about the safety of larger amounts of vitamin B12 during pregnancy.

LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA of vitamin B12 during lactation is 2.8 mcg daily (6243). There is insufficient reliable information available about the safety of larger amounts of vitamin B12 while breastfeeding.

(Read more about VITAMIN B12)

LIKELY SAFE ...when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of 100 mg daily in the form of pyridoxine for adults (15,6243). ...when used parenterally and appropriately. Injectable vitamin B6 (pyridoxine) is an FDA-approved prescription product (15).

POSSIBLY SAFE ...when used orally and appropriately in doses of 101-200 mg daily (6243,8558).

POSSIBLY UNSAFE ...when used orally in doses at or above 500 mg daily. High doses, especially those exceeding 1000 mg daily or total doses of 1000 grams or more, pose the most risk. However, neuropathy can occur with lower daily or total doses (6243,8195). ...when used intramuscularly in high doses and frequency due to potential for rhabdomyolysis (90795).

CHILDREN: LIKELY SAFE
when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of vitamin B6 in the form of pyridoxine 30 mg daily for children aged 1-3 years, 40 mg daily for 4-8 years, 60 mg daily for 9-13 years, and 80 mg daily for 14-18 years (6243).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in amounts exceeding the recommended dietary allowance (5049,8579,107124,107125,107135).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses, long-term (6243).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. A special sustained-release product providing vitamin B6 (pyridoxine) 75 mg daily is FDA-approved for use in pregnancy. Vitamin B6 (pyridoxine) is also considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology (111601). However, it should not be used long-term or without medical supervision and close monitoring. The tolerable upper intake level (UL) refers to vitamin B6 in the form of pyridoxine and is 80 mg daily for those aged 14-18 years and 100 mg daily for 19 years and older (6243).

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses. There is some concern that high-dose maternal vitamin B6 (pyridoxine) can cause neonatal seizures (4609,6397,8197).

LACTATION: LIKELY SAFE
when used orally in doses not exceeding the tolerable upper intake level (UL) of vitamin B6 in the form of pyridoxine 80 mg daily for those aged 14-18 years and 100 mg daily for those 19 years and older. The recommended dietary allowance (RDA) in lactating women is 2 mg daily (6243). There is insufficient reliable information available about the safety of vitamin B6 when used in higher doses in breast-feeding women.

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ADENOSINE (Adenocard) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, caffeine might decrease the vasodilatory effects of adenosine and interfere with its use prior to stress testing.  Details Some evidence shows that caffeine is a competitive inhibitor of adenosine and can reduce the vasodilatory effects of adenosine in humans (38172). However, other research shows that caffeine does not seem to affect supplemental adenosine because high interstitial levels of adenosine overcome the antagonistic effects of caffeine (11771). It is recommended that methylxanthines and methylxanthine-containing products be stopped 24 hours prior to pharmacological stress tests (11770). However, methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing (11771).

ALCOHOL (Ethanol) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use might increase levels and adverse effects of caffeine.  Details Alcohol reduces caffeine metabolism. Concomitant use of alcohol can increase caffeine serum concentrations and the risk of caffeine adverse effects (6370).

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.  Details Caffeine is reported to have antiplatelet activity. Theoretically, it might increase the risk of bleeding when used concomitantly with these agents (8028,8029); however, this interaction has not been reported in humans.

ANTIDIABETES DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = B Theoretically, taking caffeine with antidiabetes drugs might interfere with blood glucose control.  Details Data are conflicting. Reports claim that caffeine might increase or decrease blood sugar (6024,8646,114662).

CARBAMAZEPINE (Tegretol) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of carbamazepine and increase the risk for convulsions.  Details Animal research suggests that taking caffeine can lower the anticonvulsant effects of carbamazepine and can induce seizures when taken in doses above 400 mg/kg (23559,23561). Human research has shown that taking caffeine 300 mg in three divided doses along with carbamazepine 200 mg reduces the bioavailability of carbamazepine by 32% and prolongs the plasma half-life of carbamazepine 2-fold in healthy individuals (23562).

CIMETIDINE (Tagamet) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Likely •  Level of Evidence = B Theoretically, cimetidine might increase the levels and adverse effects of caffeine.  Details Cimetidine decreases the rate of caffeine clearance by 31% to 42% (11736).

CLOZAPINE (Clozaril) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Caffeine might increase the levels and adverse effects of clozapine and acutely exacerbate psychotic symptoms.  Details Caffeine might increase the effects and toxicity of clozapine. Caffeine doses of 400-1000 mg per day inhibit clozapine metabolism (5051). Clozapine is metabolized by cytochrome P450 1A2 (CYP1A2). Although researchers speculate that caffeine might inhibit CYP1A2, there is no reliable evidence that caffeine affects CYP1A2. There is also speculation that genetic factors might make some patients more sensitive to an interaction between clozapine and caffeine (13741). In one case report, severe, life-threatening clozapine toxicity and multiorgan system failure occurred in a patient with schizophrenia stabilized on clozapine who consumed caffeine 600 mg daily (108817).

CONTRACEPTIVE DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, contraceptive drugs might increase the levels and adverse effects of caffeine.  Details Oral contraceptives decrease the rate of caffeine clearance by 40-65% (2714,11737).

CYTOCHROME P450 1A2 (CYP1A2) INHIBITORS Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use might increase the levels and adverse effects of caffeine.  Details Caffeine is metabolized by CYP1A2. Theoretically, drugs that inhibit CYP1A2 may decrease the rate of caffeine clearance and increase caffeine levels (5051,11741).

DIPYRIDAMOLE (Persantine) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, caffeine might decrease the vasodilatory effects of dipyridamole and interfere with its use prior to stress testing.  Details Caffeine inhibits dipyridamole-induced vasodilation (11770,11772). It is recommended that methylxanthines and methylxanthine-containing products be stopped 24 hours prior to pharmacological stress tests (11770). Methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing (11771).

DISULFIRAM (Antabuse) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, disulfiram use might increase the levels and adverse effects of caffeine.  Details Disulfiram decreases the rate of caffeine clearance (11840).

DIURETIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, using caffeine with diuretic drugs might increase the risk of hypokalemia.  Details Caffeine, especially in excessive amounts, can reduce potassium levels due to stimulation of the sodium-potassium pump (23579,37905,37953,38003,38034). Diuretics can also cause lower potassium levels.

EPHEDRINE Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use might increase the risk for stimulant adverse effects.  Details Use of ephedrine with caffeine can increase the risk of stimulatory adverse effects. There is evidence that using ephedrine with caffeine might increase the risk of serious life-threatening or debilitating adverse effects such as hypertension, myocardial infarction, stroke, seizures, and death (1275,6486,10307).

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, estrogens might increase the levels and adverse effects of caffeine.  Details Estrogen inhibits caffeine metabolism (2714,23570).

ETHOSUXIMIDE (Zarontin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of ethosuximide and increase the risk for convulsions.  Details Animal research suggests that caffeine 92.4 mg/kg can decrease the anticonvulsant activity of ethosuximide (23560). However, this effect has not been reported in humans.

FELBAMATE (Felbatol) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of felbamate and increase the risk for convulsions.  Details Animal research suggests that a high dose of caffeine 161.7 mg/kg can decreases the anticonvulsant activity of felbamate (23563). However, this effect has not been reported in humans.

FLUCONAZOLE (Diflucan) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, fluconazole might increase the levels and adverse effects of caffeine.  Details Fluconazole decreases caffeine clearance by approximately 25% (11022).

FLUTAMIDE (Eulexin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, caffeine might increase the levels and adverse effects of flutamide.  Details In vitro evidence suggests that caffeine can inhibit the metabolism of flutamide (23553). However, this effect has not been reported in humans.

FLUVOXAMINE (Luvox) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = D Theoretically, fluvoxamine might increase the levels and adverse effects of caffeine.  Details Fluvoxamine reduces caffeine metabolism (6370).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Abrupt caffeine withdrawal might increase the levels and adverse effects of lithium.  Details Caffeine has diuretic activity. When abruptly discontinued, caffeine may alter the clearance of lithium (609). There are two case reports of lithium tremor that worsened upon abrupt coffee withdrawal (610) and 6 case reports of elevated serum lithium levels after reducing or eliminating caffeine intake (114665). In one case, a male with schizoaffective disorder stabilized on lithium had an elevated lithium level after reducing his caffeine intake by 87%. At a later date, he increased his caffeine intake by 6-fold, resulting in a subtherapeutic lithium level and a recurrence of psychiatric symptoms (114665).

METFORMIN (Glucophage) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, metformin might increase the levels and adverse effects of caffeine.  Details Animal research suggests that metformin can reduce caffeine metabolism (23571). However, this effect has not been reported in humans.

METHOXSALEN (Oxsoralen) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, methoxsalen might increase the levels and adverse effects of caffeine.  Details Methoxsalen reduces caffeine metabolism (23572).

MEXILETINE (Mexitil) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, mexiletine might increase the levels and adverse effects of caffeine.  Details Mexiletine reduces caffeine metabolism (1260,11741).

MONOAMINE OXIDASE INHIBITORS (MAOIs) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use might increase the risk of a hypertensive crisis.  Details Caffeine has been shown to inhibit monoamine oxidase (MAO) A and B in laboratory studies (37724,37877,37912,38108). Concomitant intake of large amounts of caffeine with MAOIs might precipitate a hypertensive crisis (15). In a case report, a patient that consumed 10-12 cups of caffeinated coffee and took the MAOI tranylcypromine presented with severe hypertension (91086). Hypertension was resolved after the patient switched to drinking decaffeinated coffee.

NICOTINE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, concomitant use might increase the risk of hypertension.  Details Concomitant use of caffeine and nicotine has been shown to have additive cardiovascular effects, including increased heart rate and blood pressure. Blood pressure was increased by 10.8/12.4 mmHg when the agents were used concomitantly (36549).

PENTOBARBITAL (Nembutal) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, caffeine might decrease the effects of pentobarbital.  Details Caffeine might negate the hypnotic effects of pentobarbital (13742).

PHENOBARBITAL (Luminal) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of phenobarbital and increase the risk for convulsions.  Details Animal research suggests that caffeine can decrease the anticonvulsant activity of phenobarbital (23558,23559,23561). However, the exact mechanism of this interaction is unclear.

PHENOTHIAZINES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, phenothiazines might increase the levels and adverse effects of caffeine.  Details Phenothiazines, including perazine, chlorpromazine, levomepromazine, and thioridazine, can reduce the metabolism of caffeine by inhibiting cytochrome P450 1A2 (CYP1A2) (23573,23574).

PHENYLPROPANOLAMINE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, phenylpropanolamine might increase the risk of hypertension, as well as the levels and adverse effects of caffeine.  Details Concomitant use of phenylpropanolamine and caffeine might cause an additive increase in blood pressure (11738). Phenylpropanolamine also seems to increase caffeine serum levels (13743).

PHENYTOIN (Dilantin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of phenytoin and increase the risk for convulsions.  Details Animal research suggests that caffeine can decrease the anticonvulsant activity of phenytoin (23559,23561). The effect does not seem to be related to the seizure threshold-lowering effects of caffeine. However, the exact mechanism of this interaction is unclear.

PIOGLITAZONE (Actos) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might increase the levels and clinical effects of pioglitazone.  Details Animal research suggests that caffeine can modestly increase the maximum concentration, area under the curve, and half-life of pioglitazone, and also reduce its clearance. This increased the antidiabetic effects of pioglitazone (108812). However, the exact mechanism of this interaction is unclear.

QUINOLONE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, quinolone antibiotics might increase the levels and adverse effects of caffeine.  Details Quinolones (also called fluoroquinolones) can decrease caffeine clearance by inhibiting cytochrome P450 1A2 (CYP1A2) enzyme (606,607,608,23554,23555,23556).

RILUZOLE (Rilutek) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use might increase the levels and adverse effects of both caffeine and riluzole.  Details Caffeine and riluzole are both metabolized by cytochrome P450 1A2 (CYP1A2), and concomitant use might reduce the metabolism of one or both agents (11739).

STIMULANT DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, concomitant use might increase stimulant adverse effects.  Details Due to the central nervous system (CNS) stimulant effects of caffeine, concomitant use with stimulant drugs can increase the risk of adverse effects (11832).

TERBINAFINE (Lamisil) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, terbinafine might increase the levels and adverse effects of caffeine.  Details Terbinafine decreases the clearance of intravenous caffeine by 19% (11740).

THEOPHYLLINE Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = C Theoretically, caffeine might increase the levels and adverse effects of theophylline.  Details Large amounts of caffeine might inhibit theophylline metabolism (11741).

TIAGABINE (Gabitril) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might increase the levels and adverse effects of tiagabine.  Details Animal research suggests that chronic caffeine administration can increase the serum concentrations of tiagabine. However, concomitant use does not seem to reduce the antiepileptic effects of tiagabine (23561).

TICLOPIDINE (Ticlid) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, ticlopidine might increase the levels and adverse effects of caffeine.  Details In vitro evidence suggests that ticlopidine can inhibit caffeine metabolism (23557). However, this effect has not been reported in humans.

VALPROATE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, caffeine might reduce the effects of valproate and increase the risk for convulsions.  Details Animal research suggests that caffeine can decrease the anticonvulsant activity of valproate (23558,23559,23561,37882). However, the exact mechanism of this interaction is unclear.

VERAPAMIL (Calan, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, verapamil might increase the levels and adverse effects of caffeine.  Details Verapamil increases plasma caffeine concentrations by 25% (11741).

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ALUMINUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Calcium citrate might increase aluminum absorption and toxicity. Other types of calcium do not increase aluminum absorption.  Details Calcium citrate can increase the absorption of aluminum when taken with aluminum hydroxide. The increase in aluminum levels may become toxic, particularly in individuals with kidney disease (21631). However, the effect of calcium citrate on aluminum absorption is due to the citrate anion rather than calcium cation. Calcium acetate does not appear to increase aluminum absorption (93006).

BISPHOSPHONATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Calcium reduces the absorption of bisphosphonates.  Details Advise patients to take bisphosphonates at least 30 minutes before calcium, but preferably at a different time of day. Calcium supplements decrease absorption of bisphosphonates (12937).

CALCIPOTRIENE (Dovonex) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Taking calcipotriene with calcium might increase the risk for hypercalcemia.  Details Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia (12938). Theoretically, combining calcipotriene with calcium supplements might increase the risk of hypercalcemia.

CALCIUM CHANNEL BLOCKERS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Intravenous calcium may decrease the effects of calcium channel blockers; oral calcium is unlikely to have this effect.  Details Intravenous calcium is used to decrease the effects of calcium channel blockers in the management of overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects (6124). But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers (12939,12947).

CEFTRIAXONE (Rocephin) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Co-administration of intravenous calcium and ceftriaxone can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys.  Details Avoid administering intravenous calcium in any form, such as parenteral nutrition or Lactated Ringers, within 48 hours of intravenous ceftriaxone. Case reports in neonates show that administering intravenous ceftriaxone and calcium can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys. In several cases, neonates have died as a result of this interaction (15794,21632). So far there are no reports in adults; however, there is still concern that this interaction might occur in adults.

DIGOXIN (Lanoxin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Using intravenous calcium with digoxin might increase the risk of fatal cardiac arrhythmias.  Details Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin (12940). However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin (38960).

DILTIAZEM (Cardizem, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, calcium may reduce the therapeutic effects of diltiazem.  Details Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, calcium might increase this risk of hypercalcemia and reduce the effectiveness of diltiazem.

DOLUTEGRAVIR (Tivicay) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce levels of dolutegravir.  Details Advise patients to take dolutegravir either 2 hours before or 6 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium carbonate 1200 mg concomitantly with dolutegravir 50 mg reduces plasma levels of dolutegravir by almost 40%. Calcium appears to decrease levels of dolutegravir through chelation (93578).

ELVITEGRAVIR (Vitekta) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce levels of elvitegravir.  Details Advise patients to take elvitegravir either 2 hours before or 2 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium along with elvitegravir can reduce blood levels of elvitegravir through chelation (94166).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce the absorption and effectiveness of levothyroxine.  Details Advise patients to take levothyroxine and calcium supplements at least 4 hours apart. Calcium reduces levothyroxine absorption, probably by forming insoluble complexes (5082). Calcium carbonate supplements reduce effectiveness of levothyroxine in patients with hypothyroidism (5081,5082,6137).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, concomitant use of calcium and lithium may increase this risk of hypercalcemia.  Details Clinical research suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients (38953). Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

QUINOLONE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Calcium seems to reduce the absorption of quinolone antibiotics.  Details Advise patients to take oral quinolones at least 2 hours before or 4-6 hours after calcium supplements or calcium-fortified foods. Taking calcium at the same time as oral quinolones can reduce quinolone absorption. Calcium binds to quinolones in the gut (4412,10339,21638,38570).

RALTEGRAVIR (Isentress) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Calcium may reduce levels of raltegravir.  Details Pharmacokinetic research shows that taking a single dose of calcium carbonate 3000 mg along with raltegravir 400 mg twice daily modestly decreases the mean area under the curve of raltegravir, but the decrease does not necessitate a dose adjustment of raltegravir (94164). However, a case of elevated HIV-1 RNA levels and documented resistance to raltegravir has been reported for a patient taking calcium carbonate 1 gram three times daily plus vitamin D3 (cholecalciferol) 400 IU three times daily in combination with raltegravir 400 mg twice daily for 11 months. It is thought that calcium reduced raltegravir levels by chelation, leading to treatment failure (94165).

SOTALOL (Betapace) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Calcium seems to reduce the absorption of sotalol.  Details Advise patients to separate doses by at least 2 hours before or 4-6 hours after calcium. Calcium appears to reduce the absorption of sotalol, probably by forming insoluble complexes (10018).

TETRACYCLINE ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Calcium seems to reduce the absorption of tetracycline antibiotics.  Details Advise patients to take oral tetracyclines at least 2 hours before, or 4-6 hours after calcium supplements. Taking calcium at the same time as oral tetracyclines can reduce tetracycline absorption. Calcium binds to tetracyclines in the gut (1843).

THIAZIDE DIURETICS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Taking calcium along with thiazides might increase the risk of hypercalcemia and renal failure.  Details Thiazides reduce calcium excretion by the kidneys (1902). Using thiazides along with moderately large amounts of calcium carbonate increases the risk of milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure). Patients may need to have their serum calcium levels and/or parathyroid function monitored regularly.

VERAPAMIL (Calan, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, calcium may reduce the therapeutic effects of verapamil.  Details Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, use of calcium supplements may increase this risk of hypercalcemia and reduce the effectiveness of verapamil.

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(Read more about CREATINE)