Mr Hyde NitroX Sour Green Apple [Discontinued] by PS ProSupps

Alpha hydroxy acids represent a group of natural chemicals that are used alone or in combination. See specific monographs for effectiveness information.

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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). 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). Doses above 10 mg/kg daily reduce the risk of apnea, bronchopulmonary dysplasia, and problematic extubation compared with doses below 10 mg/kg/day (98807,100364). 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). 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

• 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

• Athletic performance. Oral caffeine taken 30-150 minutes prior to physical activity seems to modestly improve muscle strength and physical endurance, although the magnitude of effect is variable and may be dependent on a number of patient- and activity-specific factors. Caffeine in excess of 800 mg daily can result in 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, muscle strength, physical endurance, and athletic performance (10203,11832,37648,37894,38054,38063,95955,100362,100365,100371)(103701,103703,108798,111250). Meta-analyses of studies using caffeine 3-9 mg/kg as a single dose prior to endurance time trials reports 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). Another meta-analysis of small clinical trials shows that the benefit of caffeine on athletic performance seems to increase with increased duration of the 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). 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. 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. 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). 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 very small study in healthy males shows that taking caffeine alone, 6 mg/kg prior to bench press exercises, has a greater ergogenic benefit than a multi-ingredient supplement containing the same dose of caffeine in combination with L-tyrosine, beta-alanine, L-citrulline maleate, arginine alpha-ketoglutarate, and L-taurine (111250). 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). 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), 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 further research is needed to clarify how these polymorphisms may impact the athletic performance benefits of caffeine. 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 however these studies have not demonstrated clear benefits in athletic performance over taking caffeine alone (112740).
• 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).
• 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.
• 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 resection. Details: A small clinical study in adults undergoing elective laparoscopic colon or rectal resection with primary anastomosis shows that caffeine citrate 100 mg three times daily, starting on the morning of postoperative day 1, reduces the time to self-reported first bowel movement by about 18 hours when compared with placebo. There was no difference between groups in time to self-reported first flatus (108808). Another small study in adults undergoing elective laparoscopic colectomy shows that taking caffeine 100 mg or 200 mg three times daily does not reduce the mean time to first bowel movement, colonic transit time, or length of hospital stay when compared with placebo (111484). However, a meta-analysis of these two clinical trials shows that taking caffeine does not decrease the time to the first stool or length of hospital stay when compared with control (112732).
• 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. However, it is unclear if this reduction is clinically significant. Details: Many clinical trials and observational studies show that intake of calcium supplements or dietary calcium modestly reduces 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 salt-sensitive people and patients with low baseline dietary calcium intake (945,972,974,976,984,1818,1819,1820,1821,6852)(13138,14406,38803,39063,39094,39221). Also, a meta-analysis of clinical research shows that calcium intake during pregnancy reduces systolic blood pressure in offspring by 1-2 mmHg (38852). 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 supplement 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).
• 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 in high risk pregnancies, especially if calcium intakes are low. Details: Although there is some conflicting evidence (971,38756), most clinical research shows that taking calcium orally 1-2 grams daily reduces pregnancy-related hypertension and pre-eclampsia (973,1833,8828,39043,39319,39426,96480). Calcium appears to reduce the risk of pre-eclampsia by about 50% when compared with placebo. One meta-analysis of 19 controlled trials involving over 29,000 pregnancies found that for every 19 females treated with calcium, one episode of pre-eclampsia would be avoided (96480). Calcium appears to have the greatest effect in individuals at high-risk of pre-eclampsia or with low calcium levels, and when taken at greater than or equal to 20 weeks of gestation (15029,38497,96480,99714). 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. 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 supplementation 1.5-2 grams daily during pregnancies at high risk of pre-eclampsia if dietary calcium intakes are low, in order to prevent pre-eclampsia (97347).
• 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 does not seem to be beneficial for breast cancer prevention. Details: Although some population research disagrees (15631,39041,95811,107237), most research shows that increased calcium intake is not associated with a reduced risk of breast cancer (15631,16715,98895,107236,107237). Subgroup analyses of population research suggest that calcium intake may reduce the risk of breast cancer in postmenopausal, but not pre-menopausal, adults (15631,107237). Another subgroup analysis in a large meta-analysis of population research also suggests that dietary intake may reduce estrogen receptor(ER)-negative breast cancer, but not ER-positive breast cancer (107236). However, most other 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: The most recent and robust meta-analysis of clinical research shows that calcium supplementation with or without vitamin D is NOT associated with reduced fractures in older adults without osteoporosis (95822). A large-scale study in postmenopausal females aged 50-79 years suggests 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 Women's Health Initiative study found that, in older females with the lowest genetic susceptibility to low bone mineral density (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. 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), most clinical research has found that increased calcium intake does not increase weight loss (12052,13138,15396,15399,38985,39004,97356). The most recent 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).

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).
• 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 oral calcium is beneficial for type 2 diabetes prevention. Details: Some population research has found that a higher intake of calcium from 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). However, population research is often limited by confounding variables. For example, one analysis found that any beneficial effect might be influenced by concomitant magnesium intake (96473). 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. This study is limited because it was not determined whether increased serum calcium was due to increased calcium intake or another factor such as parathyroid function (95815).
• 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).
• 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).
• Hypercholesterolemia. It is unclear if oral calcium is beneficial for hypercholesterolemia. Details: Some evidence shows that taking calcium carbonate 400 mg three times daily reduces low-density lipoprotein (LDL) cholesterol levels by 4% and increases high-density lipoprotein (HDL) cholesterol levels by 4% after 6 weeks of treatment when used in combination with a low-fat diet (American Heart Association Step 1) (2557). In contrast, a study in females with dyslipidemia shows that taking calcium 800 mg daily for 2 years might INCREASE total cholesterol levels by about 12 mg/dL when compared with placebo. This same study showed an association between calcium supplementation and an increase in total cholesterol levels and carotid intimal thickness in postmenopausal females, but not premenopausal females (97350). A recent meta-analysis of randomized controlled trials which included both healthy patients and patients with 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 more effective in patients with dyslipidemia at baseline. It is unclear if this effect is due to calcium, vitamin D, or the combination (107227). However, other research shows that taking a specific supplement containing calcium 600 mg plus vitamin D 200 IU (Caltrate 600 D, Wyeth Consumer Healthcare Inc.) twice daily in combination with calorie restriction does not reduce total or LDL cholesterol levels when compared with placebo (15601).
• 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).
• 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.

(Read more about CALCIUM)

POSSIBLY INEFFECTIVE

• Athletic performance. Taking oral choline before exercise does not improve athletic performance. Details: Clinical research in trained athletes shows that taking oral choline 2.43 grams as a single dose does not delay fatigue during endurance sports when compared with placebo (5164). Other clinical research in untrained adults shows that taking oral choline 8.425 grams or 50 mg/kg once prior to participating in exhaustive, load-carrying exercise does not improve dexterity, upper or lower body strength, grip strength, or run time-to-exhaustion following exercise when compared with placebo (42229,42237).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral choline is beneficial in patients with age-related cognitive decline. Details: Small clinical studies in adults with memory loss shows that taking choline 2 grams four times daily orally for 21 days does not improve memory when compared with placebo (5170). Observational research in adults over 60 years of age has found that intake of choline 187-399.5 mg daily is associated with a 33% to 42% reduced odds of low cognitive function when compared with intake of less than 187 mg daily. Intake of more than 399.5 mg daily was not associated with low cognitive function when compared with less than 187 mg daily (109100).
• Allergic rhinitis (hay fever). It is unclear if oral choline is beneficial in patients with allergic rhinitis. Details: Preliminary clinical research shows that taking oral choline, as tricholine citrate, 500 mg three times daily for 8 weeks is less effective than intranasal budesonide 200 mcg twice daily for reducing symptoms of allergic rhinitis (42252).
• Alzheimer disease. Although there has been interest in using oral choline for Alzheimer disease, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Asthma. Small clinical studies suggest that oral choline may modestly improve symptoms in patients with asthma. Details: Preliminary clinical research shows that taking choline 500-1000 mg orally three times daily for 3-4 months decreases the severity of symptoms, the number of symptomatic days, and the need to use bronchodilators in patients with asthma when compared with placebo (5165,5166). Preliminary data also shows that choline 3 grams daily might be more effective than 1.5 grams daily (5165).
• Autism spectrum disorder. Oral choline 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 donepezil 2.5-5 mg daily and choline bitartrate 350 mg daily for 12 weeks improves receptive language skills, but no other outcomes, for up to 6 months after treatment when compared with placebo in children aged 5-10 years with autism spectrum disorder. Also, adolescents aged 11-16 years experienced no benefits, and some experienced an increase in behavioral symptoms, such as irritability (103571). It is unclear if this effect is due to choline, donepezil, or the combination.
• Breast Cancer. It is unclear if dietary intake of choline reduces the risk of breast cancer. Details: A meta-analysis of 6 low to moderate-quality observational studies suggests that neither high nor low dietary intake of choline is associated with breast cancer risk. This finding is largely influenced by inclusion of the European Prospective Investigation into Cancer and nutrition (EPIC) cohort study, which analyzed data from over 300,000 subjects. However, subanalysis of 3 case-control studies suggests that high dietary intake of choline may be associated with a decreased risk of breast cancer when compared with low choline intake (111416). The interpretation of these findings is limited by the heterogeneity of the included studies, self-reported data, and a small number of studies.
• Bronchitis. Although there has been interest in using oral and inhaled choline for bronchitis, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Cancer. It is unclear if dietary choline intake reduces the risk for cancer. Details: A meta-analysis of 11 low-quality population studies has found that high dietary intake of choline is associated with an 18% lower risk of cancer when compared with low choline intake. High dietary intake of both choline and betaine was associated with a 40% lower risk of cancer (97390).
• Cardiovascular disease (CVD). It is unclear if dietary choline intake reduces the risk of CVD or improves outcomes in patients with CVD. Details: A meta-analysis of population research has found that high intake of dietary choline is not associated with a lower risk of coronary artery disease, stroke, or mortality when compared with a diet low in choline (97388). A more recent population study has found that energy-adjusted total choline intake is not associated with the incidence of CVD over ten years. However, the highest intake of free choline is associated with a 34% reduced risk of CVD when compared with the lowest intake (109104).
• Cerebellar ataxia. It is unclear if oral choline is beneficial in patients with cerebellar ataxia. Details: Despite some anecdotal reports suggesting that taking choline improves motor function, preliminary clinical research shows that taking choline 4-5 grams orally daily for 4 days to 6 weeks does not reduce cerebellar ataxia (5161,5173,23679).
• Cognitive function. It is unclear if oral choline is beneficial for improving cognitive function in healthy adults. Details: Preliminary clinical research shows that taking a single dose of choline 50 mg/kg orally prior to participating in an exhaustive, load-carrying task does not improve reaction time, reasoning, memory, or serial addition and subtraction ability following the task when compared with placebo (42237). Also, preliminary clinical research in patients requiring long-term total parenteral nutrition (TPN) shows that adding choline chloride 2 grams daily to TPN for 24 weeks might improve delayed visual memory, but does not improve other measures of cognitive performance, when compared with TPN alone (42232).
• Cirrhosis. Although there has been interest in using oral choline for cirrhosis, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Complex partial seizures. Although there has been interest in using oral choline for complex partial seizures, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Dementia. Although there has been interest in using oral choline for dementia, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Depression. It is unclear if oral choline is beneficial for the treatment or prevention of depression. Details: Observational research has found that dietary choline intake of at least 198 mg daily is associated with a 32% to 43% decreased risk of depressive symptoms when compared with intakes of less than 198 mg daily (109106). It is unclear if choline supplementation is beneficial for depression.
• Diabetes. It is unclear if oral choline is beneficial for the treatment or prevention of type 2 diabetes; the available research is conflicting. Details: Preliminary clinical research shows that taking oral choline bitartrate 1000 mg daily for 2 months does not affect coagulation parameters or levels of triglycerides, low-density lipoprotein (LDL) cholesterol, or high-density lipoprotein (HDL) cholesterol in patients with type 2 diabetes (103569). Choline has also been evaluated for the prevention of type 2 diabetes. In Finnish males, observational research has found that dietary intake of total choline at levels of more than 482 mg daily, especially as phosphatidylcholine, is associated with a 25% lower risk of developing type 2 diabetes over the following 19.3 years when compared with intakes of less than 382 mg daily (103567). However, in males and females in the US, additional observational research has found no association between dietary choline and risk of type 2 diabetes over a mean of 9 years (103570). In addition, a sub-analysis found that the highest intakes of choline (a median of 487 mg daily) were associated with a 54% higher risk of type 2 diabetes among females, but not males, when compared with the lowest intakes (a median of 175 mg daily) (103570). Population research in patients with diabetes has found that an intake of dietary choline in amounts of at least 279 mg daily is associated with a 2.1-fold increased odds of diabetic retinopathy in females, but not males, when compared with an intake less than 206 mg daily (109102). It is unclear if choline itself is responsible for the increased odds of diabetic retinopathy in this population.
• Fetal alcohol spectrum disorders (FASD). It is unclear if oral choline improves cognition in children with fetal alcohol spectrum disorders (FASD). Details: Clinical research in children aged 2.5-5 years with FASD shows that taking oral choline bitartrate, providing choline 500 mg, daily for 9 months does not improve global cognitive development or hippocampal-dependent memory when compared with placebo. However, a subgroup analysis of only children aged 2.5-4 years suggests that choline may improve hippocampal-dependent memory (92112). Follow-up of this study at 7 years shows that choline improves motor speed and suggests a trend towards improved color naming, which are components of executive functioning testing, when compared with placebo (111745). The validity of these findings is limited by the high rate of patient discontinuation which limits statistical power. A small clinical trial in children 5-10 years old with FASD shows that taking oral glycerophosphocholine, providing choline 625 mg, daily for 6 weeks does not improve cognitive function, executive function, attention, or hyperactivity when compared with placebo (97389).
• Hepatitis. Although there has been interest in using oral choline for hepatitis, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Huntington disease. Although there has been interest in using oral choline for Huntington disease, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Hypertension. It is unclear if oral choline is beneficial for the prevention or treatment of hypertension. Details: Population research has found that every 100-mg increase in daily dietary choline intake is associated with a 15% decreased risk of developing hypertension over the next 4.6 to 9.1 years (109098). However, it is unclear if any benefits are specifically related to dietary choline or whether choline supplementation is beneficial.
• Infant development. It is unclear if oral choline intake during pregnancy is beneficial for infant development; the available research is conflicting. Details: Two observational studies have found that higher intake of choline during the second and third trimesters of pregnancy is associated with improvement in offspring cognitive development and visual memory at the age of 18 months and 7 years, respectively, when compared with lower choline intake (94654,94657). One of these studies found that each 1 mcmol/L increase in maternal blood levels of choline at 16 weeks' gestation was associated with a 2.23-point increase in cognitive skill score based on the Bayley Scales of Infant Development (BSID-III) at 18 months of age (94657). Also, some observational research has found that higher plasma levels of choline during pregnancy are associated with higher processing speed and decreased social withdrawal at 4 years of age in the offspring (109101). In contrast, 3 observational studies have found that higher intake of choline during pregnancy, as well as higher maternal and cord blood levels of choline, are not associated with improved offspring intelligence at 5 years of age or cognitive performance at 3 or 7 years of age (94654,94655,94656). However, many of these observational studies, including those with positive findings, included populations with a mean intake of choline that was below the recommended adequate intake of 450 mg daily (94654,94656). It's possible that higher intake of choline is needed to observe a benefit; however, research on the effects of choline supplementation is limited. One small clinical trial shows that taking choline 930 mg daily during the third trimester modestly improves sustained attention in the child at 7 years of age when compared with taking 480 mg daily (109105).
• Metabolic syndrome. It is unclear if oral choline is beneficial in patients with metabolic syndrome. Details: Preliminary clinical research in adults with metabolic syndrome shows that taking oral choline 400 mg daily for 4 weeks does not decrease body weight, blood pressure, plasma glucose levels, or low-density lipoprotein (LDL) cholesterol levels, or increase high-density lipoprotein (HDL) cholesterol levels, when compared with baseline (105731).
• Neural tube birth defects. It is unclear if oral choline intake is beneficial for preventing neural tube defects. Details: Population research has found that females who have a high dietary choline intake around the time of conception have a lower risk of having offspring with a neural tube defect when compared to those with lower intake (13134).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral choline is beneficial in patients with nonalcoholic fatty liver disease (NAFLD). Details: A cross-sectional analysis of results from observational and clinical research shows that low dietary intake of choline is associated with increased fibrosis in postmenopausal adults with NAFLD, but not in children, males, or premenopausal adults with NAFLD. Dietary choline intake was not associated with steatosis severity in any patient subgroup (92109).
• Schizophrenia. Although there has been interest in using oral choline for schizophrenia, there is insufficient reliable information about the clinical effects of choline for this purpose.
• Tourette syndrome. Although there has been interest in using oral choline for Tourette syndrome, there is insufficient reliable information about the clinical effects of choline for this purpose.
• TPN-associated hepatic steatosis. It is unclear if intravenous choline is beneficial in patients with TPN-associated hepatic steatosis. Details: In patients receiving long-term total parenteral nutrition (TPN), plasma levels of choline can decrease. Small, low-quality clinical studies show that administering intravenous choline 1-4 grams daily for 24 weeks improves some markers of TPN-associated hepatic steatosis when compared with baseline or placebo (5174,42235). More evidence is needed to rate choline for these uses.

(Read more about CHOLINE)

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 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 a variety of other ergogenic supplement ingredients. However, research is conflicting and variable and any benefits may be dose- and/or population-dependent.
• 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 24 weeks (90323,90330,93626,93627,108316,108336). 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 upper limb strength and lower limb strength, with a small-to-moderate overall effect (93626,93627). Benefits in combination with resistance training have also been shown on upper and/or lower limb strength in older adults, although benefits on both have not been demonstrated in all analyses (90323,90330,108316,108336). 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 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, significant decreases in fat mass are lacking and effects on body fat percentage are inconsistent (90323,108335). 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), 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 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 seem to 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 kidney disease (CKD). It is unclear if oral creatine is beneficial in patients with CKD. Details: A small clinical study in CKD patients undergoing hemodialysis shows that taking creatine monohydrate 20 grams daily for a week alternating with taking 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).
• 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 preliminary clinical research in healthy adults shows that taking a specific creatine (Creapure, AlzChem) 10-20 grams orally daily for 6 weeks does not improve cognitive function scores when compared with placebo (112215).
• 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.
• 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 patients 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 patients with schizophrenia when compared with placebo (16390).
• 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)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Anxiety. Although there has been interest in using oral GABA for anxiety, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Athletic performance. Although there has been interest in using sublingual GABA for athletic performance, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral GABA for ADHD, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Cerebral palsy. It is unclear if oral GABA is beneficial for cerebral palsy in children. Details: Preliminary clinical research in children with cerebral palsy shows that taking a specific product containing GABA (Gammalon) one to four tablets daily (depending on age) for 2 months, in addition to standard therapy for cerebral palsy, improves mental development, learning, vocabulary, physical function, motor strength and activity, and motor hyperactivity in a greater percentage of children when compared with standard therapy alone (19362). These findings are limited by poor study design.
• Chronic bronchitis. It is unclear if oral GABA is beneficial for chronic bronchitis. Details: Preliminary clinical research in adults with chronic bronchitis shows that taking a specific GABA product (Aminalon) 1.5-3 grams daily for 18-20 days, along with conventional treatment for acute exacerbations of bronchitis, increases the duration of subsequent remission by about 3 months when compared with conventional treatment alone (19361).
• Cushing syndrome. It is unclear if oral GABA is beneficial for Cushing syndrome. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 1-3 grams daily for one month decreases plasma levels of adrenocorticotropic hormone (ACTH) 60 minutes after administration, as well as cortisol and ACTH levels up to 2 days after GABA discontinuation, when compared with baseline (19363). The validity of these findings is limited by the lack of a comparator group.
• Depression. Although there has been interest in using oral GABA for depression, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Epilepsy. It is unclear if oral GABA is beneficial for epilepsy. Details: Preliminary clinical research shows that taking a combination of GABA 2.5-3 grams and phosphatidylserine 500 mg daily for 3-8 months reduces seizure frequency when compared with placebo in patients with absence seizures, but not in those with focal aware or focal impaired awareness seizures (19364). Other preliminary clinical research suggests that taking GABA 3 grams with phosphatidylserine 600-1200 mg daily for 2 days does not affect the seizure photosensitivity range in people with photoconvulsive responses (5113).
• Hypertension. Preliminary clinical research suggests that oral GABA may modestly reduce blood pressure in patients with mild or borderline hypertension. Details: Preliminary clinical research in adults with hypertension shows that drinking 100 mL of fermented milk containing GABA 10-12 mg daily at breakfast for 12 weeks reduces systolic and diastolic blood pressure by about 17 mmHg and 7 mmHg, respectively, when compared with baseline. Compared with patients treated with a placebo milk, these reductions were significant. However, it is unclear if the placebo milk also differed from the fermented milk in other ways (19367). Other preliminary clinical research in patients with borderline hypertension shows that taking a chlorella supplement containing GABA 20 mg twice daily for 12 weeks reduces systolic blood pressure when compared with placebo (19368). However, these findings are limited by poor study design.
• Insomnia. It is unclear if oral GABA is beneficial for insomnia. Details: Two small clinical studies in adults with insomnia show that taking fermented rice germ extract, standardized to provide GABA 75 mg or 300 mg, one hour before bedtime for 4 weeks modestly decreases sleep latency when compared with placebo, but does not improve sleep efficacy or reduce episodes of waking after sleep onset (110134,110135). As these doses were evaluated in separate studies, no direct comparison between GABA 75 mg and 300 mg has been conducted.
• Meningitis. It is unclear if oral GABA is beneficial for meningitis. Details: Preliminary clinical research in children aged 7 months to 16 years with meningitis shows that taking a specific GABA product (Aminalon) 0.5-1.5 grams daily, starting within 2-4 weeks of illness and continuing for one month thereafter, decreases the incidence of residual disease manifestations and prevents the development of cerebrospinal syndrome when compared with control (19369). However, this study was conducted prior to the development of current treatment guidelines for meningitis; it is unclear if GABA is beneficial when used in conjunction with current standard care.
• Menopausal symptoms. Although there has been interest in using oral GABA for menopausal symptoms, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Motion sickness. It is unclear if oral GABA is beneficial for motion sickness. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 0.5 grams as a single dose 40-50 minutes before induced motion sickness or three times daily for 4 days significantly delays onset of motion sickness when compared with placebo. GABA also decreases the occurrence of motion sickness symptoms including chills, cold sweats, and pallor when compared with placebo (19370).
• Obesity. Although there has been interest in using oral and sublingual GABA for weight loss, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Pain (acute). Although there has been interest in using oral and sublingual GABA for acute pain, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Post-traumatic stress disorder (PTSD). Although there has been interest in using oral GABA for PTSD, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Prediabetes. It is unclear if oral GABA is beneficial for prediabetes. Details: A small clinical study in adults with prediabetes and overweight or obesity shows that taking GABA 500 mg (GABA, Swanson Health) 3 times daily for 95 days does not improve postprandial glucose response to oral glucose tolerance testing, fasting glucose, glycated hemoglobin (HbA1c), or glycemic variability when compared with placebo (112830).
• Premenstrual syndrome (PMS). Although there has been interest in using oral GABA for PMS, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Psychological well-being. Although there has been interest in using oral and sublingual GABA to improve well-being, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Stress. It is unclear if oral GABA is beneficial for stress. Details: Preliminary clinical research shows that taking a single dose of GABA 100-200 mg by mouth 10-70 minutes prior to completing a mentally stressful task does not appear to reduce subjective measure of stress when compared with placebo (90568). However, it does attenuate alpha wave reduction and reduces beta wave upsurge on the EEG during testing when compared with placebo (19373,90568). More evidence is needed to rate GABA for these uses.

(Read more about GAMMA-AMINOBUTYRIC ACID (GABA))

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. 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). However, due to the lack of benefit seen with the use of L-arginine alone, it is possible that this effect is due to the other ingredients or the combination of ingredients.

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).
• 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).
• 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.
• 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)

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).

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)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Athletic performance. Preliminary clinical research shows that theacrine does not improve measures of athletic performance. However, these studies were small, and may have been underpowered. Details: One small clinical trial in elite male and female soccer players shows that taking theacrine (TeaCrine, Compound Solutions, Inc.) 275 mg alone or 125 mg in combination with caffeine 150 mg 30 minutes prior to exercise does not improve time to exhaustion, control of heart rate, or perceived exertion when compared with placebo (99950). Another small clinical trial in resistance trained males shows that taking theacrine (TeaCrine, Compound Solutions, Inc.) 300 mg alone or 150 mg in combination with caffeine 150 mg 90 minutes prior to exercise does not improve endurance or rowing time trial performance when compared with placebo (103274).
• Cognitive function. Oral theacrine has mostly been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking theacrine does not improve concentration or most other measures of cognitive function (88784,99950,99952). Studies have used single doses of 200-275 mg of a specific theacrine product (TeaCrine; Compound Solutions, Inc.) alone, in combination with caffeine 150 mg, or in a proprietary combination with caffeine 150 mg, white willow bark, SAMe, Rauwolfia vomitoria, vitamin B12, and citrus bioflavonoids (TheaTrim, Purus Labs). However, the validity of these results is limited because the studies were likely underpowered. Furthermore, some research shows that taking theacrine 200 mg daily for 7 days might improve subjective measures of cognitive function, such as increased energy, reduced fatigue, and improved concentration, in some healthy individuals (88784). A small clinical study in young males shows that taking a combination product containing theacrine 50mg, caffeine 125 mg, and methylliberine 75mg as a single dose orally before a video game test improves inhibitory control, attention to internal processing, reaction times, and self-reported alertness when compared with either caffeine 125 mg alone or placebo. Caffeine alone is associated with increased anxiety and headache when compared with taking the combination product (109926).
• Fatigue. Although there is interest in using oral theacrine for fatigue, there is insufficient reliable information about the effects of theacrine for this purpose.
• Mental alertness. Oral theacrine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in males aged 18-63 years who are current or former law enforcement or military personnel shows that taking theacrine 50 mg, caffeine 150 mg, and methylliberine 100 mg immediately before two 75-minute consecutive computerized tests of reaction times, vigilance, and marksmanship, improves reaction times and vigilance in the second test when compared with the first. Similar improvements are seen with the combination product and with subjects taking caffeine 300 mg alone. All three groups, including placebo, show improvements in decision making and in subjective feelings of arousal when compared with baseline, but not marksmanship scores (109927).
• Muscle strength. Oral theacrine has only been evaluated in combination with caffeine; its effect when used alone is unclear. Details: A small clinical study in resistance trained males shows that taking theacrine (TeaCrine, Compound Solutions, Inc.) 300 mg alone or 150 mg in combination with caffeine 150 mg 90 minutes prior to resistance training does not improve muscle strength or power, measured by bench press and squat exercises, when compared with placebo (103274). However, the study has been inadequately powered to detect a difference between groups. More evidence is needed to rate theacrine for these uses.

(Read more about THEACRINE)

POSSIBLY EFFECTIVE

• Cognitive function. Oral L-theanine may improve some aspects of cognitive function. It is unclear if using L-theanine in conjunction with caffeine can enhance the effects of either ingredient. Details: A single dose of L-theanine 100 mg seems to improve vigilant attention, reducing error rates in cognitive tests when compared with placebo (91747). However, taking L-theanine (Suntheanine, Taiyo Kagaku) 200 mg daily for 4 weeks does not improve verbal fluency, memory, motor speed, or executive function in an adult population, although it may moderately improve verbal fluency in a subgroup of people with lower cognitive function at baseline (101986). When L-theanine is combined with caffeine, a meta-analysis and multiple individual clinical studies show that the combination improves alertness, as well as accuracy during a test that requires switching attention between different tasks, but does not improve reaction time (38116,91750,96335,96336). Some research also shows that L-theanine plus caffeine improves cognitive performance and reduces task-induced fatigue when compared with baseline and placebo. However, it is unclear if this is due to the individual ingredients or the combination (38116,96335,96336). Some research suggests that the combination is no better than either individual ingredient alone (91747,96335,96336).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral L-theanine, taken continuously or as a single dose, improves cognition in older adults. Details: A small clinical study in healthy, Japanese adults aged 50-69 years shows that taking a specific product (Suntheanine; Taiyo International.) containing L-theanine 101 mg daily after breakfast for 12 weeks does not improve mini-mental state exam (MMSE) scores when compared with placebo. However, a single-dose analysis from this study shows that administration of L-theanine 101 mg may improve the quality of working memory and reaction times during a cognitive function test when compared with placebo (108553). Patients were permitted to consume polyphenol-rich beverages during the study period; however, consumption was not documented, limiting the validity of this finding.
• Alzheimer disease. Although there is interest in using oral theanine for Alzheimer disease, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Anxiety. It is unclear if oral L-theanine is beneficial in patients with anxiety. Results of clinical research are conflicting. Details: A preliminary clinical study shows that taking a single dose of a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg does not reduce experimentally-induced anticipatory anxiety when compared with placebo (12188). However, another preliminary clinical study in healthy adults with stress-related anxiety shows that taking L-theanine 200 mg daily for 4 weeks reduces anxiety scale scores and sleep disturbance when compared with placebo (101986).
• Attention. It is unclear if oral theanine improves attention. Details: A small clinical study in healthy males shows that taking a single dose of L-theanine 200 mg improves selective attention similar to a single dose of caffeine 160 mg (96337). However, other small clinical studies in adults show that taking L-theanine 100-400 mg does not improve most measures of attention, especially sustained attention or attention in executive control tasks, but doses of 100-200 mg may improve performance in simple attentional tasks when compared with placebo (96338,111396). Some of these studies suggest that taking L-theanine with caffeine appears to provide more benefit than either individual ingredient alone (96337,96338).
• Attention deficit-hyperactivity disorder (ADHD). Oral L-theanine seems to improve some aspects of ADHD, including cognition and sleep. Details: Some preliminary clinical research in children with ADHD shows that taking a one-time dose of L-theanine 2.5 mg/kg increases cognition scores, but does not improve results on sustained attention or inhibitory control tests, when compared with placebo. Taking L-theanine with caffeine 2 mg/kg also increases cognition scores and improves performance on a sustained attention test, but does not improve inhibitory control, when compared with placebo (104141). Other preliminary clinical research in males aged 8-12 years with ADHD shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg orally twice daily for 6 weeks increases the percent of time spent in restful sleep by about 5% and decreases the number of bouts of nocturnal activity by about 6 when compared with placebo (91744).
• Cancer. Although there is interest in using oral theanine for cancer, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Chemotherapy-induced diarrhea. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with colon cancer shows that taking L-cystine 700 mg and L-theanine 280 mg (Ajinomoto Co. Inc.) orally once daily, starting one week before chemotherapy with TS-1 (Taiho Pharmaceutical) and continuing for 28 days, increases the rate of therapy completion by 49%, reduces the incidence of diarrhea by 37%, reduces appetite loss by 33%, and improves the reported tolerability of chemotherapy when compared with chemotherapy alone (96334). However, this combination does not appear to be beneficial in patients with gastric cancer, or in those with colorectal cancer receiving 4 courses of capecitabine-based adjuvant chemotherapy. (96334,101985).
• Cognitive impairment. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One very small clinical study in adults with mild cognitive impairment shows that taking a product containing L-theanine 120 mg and green tea extract 720 mg (LGNC-07, LG Household & Health Care, Ltd) orally twice daily after meals for 16 weeks modestly improves memory and attention when compared with baseline. However, taking this product does not appear to improve memory and attention when patients with self-reported memory problems, but without mild cognitive impairment, are also considered (96339).
• Depression. It is unclear if oral L-theanine is beneficial in patients with depression. Details: A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku Co. Ltd.) 250 mg at bedtime for 8 weeks reduces symptoms and improves sleep quality when compared to baseline in individuals with mild major depressive disorder (MDD) (96331). The validity of these findings is limited by the lack of a comparator group. Another small clinical study in adults with MDD shows that taking L-theanine 200 mg daily with sertraline for 6 weeks reduces depression symptoms and increases remission rates but does not improve treatment response rates when compared with sertraline and placebo (112278). The validity of these effects is limited by the small sample size and short study duration. Additionally, it is unclear if the reduction in depressive symptoms is clinically significant.
• Erythema. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy females with self-perceived skin sensitivity shows that taking a specific supplement containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne) daily for 8 weeks reduces facial pigmentation when compared to baseline (111399). The validity of this finding is limited by a lack of a placebo group. It is unclear if these effects are due to L-theanine, other ingredients, or the combination.
• Generalized anxiety disorder (GAD). It is unclear if oral L-theanine is beneficial for reducing anxiety in people with GAD. Details: One small clinical study in adults with GAD shows that taking L-theanine 225 mg twice daily for 4 weeks, then 450 mg twice daily for 4 weeks, in conjunction with prescribed antidepressants, does not reduce anxiety scores when compared with antidepressants and placebo (104976).
• Hypertension. Although there is interest in using oral theanine for hypertension, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Influenza. Oral L-theanine 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 green tea catechins (THEA-FLAN 90S, Ito-en Co.) 378 mg, standardized to contain epigallocatechin gallate 270 mg and L-theanine (Suntheanine, Taiyo Kagaku) 210 mg daily for 5 months reduces the risk of developing clinically diagnosed influenza when compared with placebo. However, the combination does not seem to prevent laboratory-confirmed influenza infection (54021).
• Insomnia. It is unclear if oral L-theanine is beneficial for insomnia. Details: A very small clinical study in young healthy adults with sleep quality worsened by caffeine intake shows that taking L-theanine 50 mg (Suntheanine, Taiyo Kagaku Co. Ltd) once 10 minutes before bedtime suppresses caffeine-induced elevations in wake after sleep onset time but does not improve parameters of sleep quality including sleep onset latency, sleep time, or number of times waking after sleep onset when compared with placebo (112275). L-theanine has also been studied in combination with other ingredients. A small clinical study in adults with insomnia or disturbed sleep patterns shows that a specific product (RLX2; LiveLife Biosciences AG) containing L-theanine 50 mg and a specific casein peptide, alpha-s1-casein tryptic hydrolysate, 150 mg, taken one hour before bedtime for 4 weeks, increases sleep duration by 45 minutes and improves habitual sleep efficiency and daytime dysfunction when compared with baseline (108556). Another very small clinical study in healthy adults shows that taking a combination product containing tryptophan, glycine, magnesium, tart cherry powder, and L-theanine 2 hours before bedtime decreases sleep onset latency and increases total sleep duration, leading to better sleep efficiency and reduced morning sleepiness, when compared with placebo (111184). Another combination product containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne), taken daily for 8 weeks, seems to improve sleep quality when compared to baseline (111399). However, the validity of this finding is limited by a lack of a control group. It is unclear if the effects described above are due to L-theanine, other ingredients, or the combination.
• Obsessive-compulsive disorder (OCD). It is unclear if oral L-theanine is beneficial for OCD. Details: A small clinical study in adults with OCD shows that taking L-theanine 100 mg twice daily for 10 weeks with fluvoxamine reduces OCD symptoms, particularly obsessive symptoms, and increases the proportion of patients with a complete response to treatment but does not improve compulsive symptoms, partial response rates, or remission rates when compared with placebo and fluvoxamine (112276).
• Postoperative recovery. Oral theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study of adults with esophageal cancer undergoing esophagectomy shows that taking theanine 280 mg and cystine 700 mg daily, staring 4 days before surgery and continued for 13 days after surgery, does not improve measures of physical activity but does improve exercise tolerance and some measures of quality of life when compared with placebo (111400). It is unclear if these findings are due to theanine, cystine, or the combination.
• Schizophrenia. It is unclear if oral L-theanine is beneficial in patients with schizophrenia; the available evidence is limited and conflicting. Details: One small preliminary clinical study in adults with schizophrenia or schizoaffective disorder shows that taking L-theanine (Biosynergy) 200 mg orally twice daily for 8 weeks along with antipsychotic medications improves positive symptoms, anxiety, and general psychopathology symptoms, such as poor impulse control and disorientation, when compared with placebo. However, theanine does not improve general disease severity, negative symptoms, depression, cognitive function, extrapyramidal side effects, or quality of life (96341). In contrast, two small clinical studies show that taking L-theanine 400 mg (Suntheanine, BioSynergy Health Alternatives) with antipsychotics and with or without pregnenolone 50 mg daily for 8 weeks reduces negative symptoms, general psychopathology symptoms, and anxiety when compared with placebo in patients with schizophrenia or schizoaffective disorder. However, there were no improvements in positive schizophrenia symptoms, extrapyramidal side effects, or symptoms of depression (97923,112277). The inconsistency of results might be due to the small study sizes and the subjectivity of the outcomes measured.
• Stress. It is unclear if oral L-theanine is beneficial in patients with stress. Details: One very small clinical study shows that taking L-theanine 200 mg prior to a stress-inducing exam reduces tension-anxiety and may prevent blood pressure increases caused by psychological stress when compared with placebo (91746). Other preliminary clinical research in pharmacy students shows that taking theanine 200 mg twice daily for one week prior, and then for the first 10 days of a pharmacy practice period, decreases subjective stress scores when compared with placebo (91745). Another small clinical study in healthy young adults shows that drinking a beverage containing L-theanine 200 mg alone or combined with L-arginine 50 mg after a psychological stressor reduces stress, as measured by salivary alpha-amylase activity, when compared with placebo. The combination of L-arginine and L-theanine did not differ from L-theanine alone, suggesting that the combination does not act synergistically to reduce markers of stress (110393). However, not all research has been positive. A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg induces subjective feelings of tranquility in relaxed people, but not those with experimentally-induced anticipatory anxiety, when compared with placebo (12188). Also, a small, clinical crossover study in healthy, moderately stressed adults shows that taking a single dose of a specific product (Alphawave; Ethical Naturals) containing L-theanine 200 mg prior to a stress-inducing exam does not improve anxiety at any time point when compared with placebo (108554). Due to the single-dose nature of this study, the effects of continued administration of this product are unclear. L-theanine has also been evaluated in combination with other ingredients. A small clinical study in adults with stress shows that taking a specific combination product (Mg-Teadiola, Sanofi-Aventis Group), containing green tea extract 125 mg (providing 50 mg L-theanine), magnesium 150 mg, vitamin B6 0.2 mg, vitamin B9 0.1 mg, vitamin B12 1.25 mcg, and rhodiola 222 mg, orally once daily for 28 days modestly improves stress and anxiety scores when compared with placebo. Improvements in stress scores, but not anxiety scores, appear to persist at 28 days after treatment completion (108672). It is unclear if any effects are due to L-theanine, other ingredients, or the combination.
• Tourette syndrome. It is unclear if oral L-theanine is beneficial in children with Tourette syndrome. 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 L-theanine 200 mg and vitamin B6 2.8 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. More evidence is needed to rate theanine for these uses.

(Read more about THEANINE)

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)

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Antidepressant-induced sexual dysfunction. It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial for patients with antidepressant-induced sexual dysfunction. Details: Small clinical trials suggest that taking yohimbine, a constituent of yohimbe, improves sexual dysfunction associated with selective serotonin reuptake inhibitors (SSRIs) (3305,3306,3307,3311,3313,3970,3971,3972,3973). It is unclear if yohimbe bark is beneficial.
• Anxiety. There is limited evidence on the oral use of yohimbine, a constituent of yohimbe, for the management of various phobias. Details: A small clinical study in healthy adults with a fear of flying shows that taking yohimbine hydrochloride 10 mg as an adjunct to virtual reality exposure therapy (VRET) does not improve anxiety measures when compared with VRET alone (86819). However, another small clinical study in healthy adults with claustrophobia shows that taking yohimbine hydrochloride 10.8 mg prior to exposure-based treatment reduces peak fear after one week when compared with exposure-based treatment alone (86794). The effect of yohimbe bark has not been investigated in clinical research.
• Athletic performance. It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial for athletic performance. Details: A small clinical study in professional soccer players shows that taking yohimbine, a constituent of yohimbe, 20 mg daily for 3 weeks does not improve exercise performance or build muscle mass when compared with placebo (86785). However, a small crossover study in physically active females undergoing an anaerobic exercise test shows that taking a single dose of oral yohimbine 2.5 mg 20 minutes prior to repeated sprints increases average power output, total work, and heart rate and decreases average fatigue index when compared with placebo. Additionally, taking yohimbine decreases lactic acid levels and increases epinephrine levels when compared with baseline or placebo (107849). Due to the single-dose nature of this study, the effects of continued administration of yohimbine on athletic performance are unclear. The effects of yohimbe bark have not been investigated in clinical research.
• Depression. It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial in patients with depression. Details: A very small clinical study in patients with treatment-resistant major depressive disorder shows that taking yohimbine, a constituent of yohimbe, 30 mg daily for 10 days along with desipramine does not improve symptoms of depression when compared with desipramine alone (86834). Also, a small crossover trial in patients with major depressive disorder and/or a history of adverse childhood experiences shows that taking yohimbine 10 mg once does not alter approach-avoidance behaviors normally associated with depression when compared with placebo (111402). The effects of yohimbe bark have not been investigated in clinical research.
• Dry mouth. It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial for dry mouth. Details: A very small clinical study shows that taking yohimbine, a constituent of yohimbe bark, 18 mg daily for 5 days improves symptoms of dry mouth in individuals treated with antidepressants when compared with placebo (86886). The effect of yohimbe bark has not been investigated in clinical research.
• Erectile dysfunction (ED). It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial for ED. Details: The effects of yohimbe bark have not been investigated in clinical research. Most small clinical studies suggest that taking yohimbine, a constituent in yohimbe bark, seems to improve symptoms in adults with various types of ED, including organic, psychogenic, mixed, and others (3305,3307,3309,3311,3312,3313,10629,86827,86831,86878)(86882,86888,86896). A meta-analysis in patients with ED shows that taking 5-100 mg of oral yohimbine for 2-10 weeks increases the probability of erectile function improvement when compared with placebo. Also, the use of yohimbine in combination with either L-arginine or trazodone, but not as monotherapy, improves sexual function when compared with placebo (107848). These findings are limited by the high heterogeneity of the included studies. Due to insufficient data, guidelines from the American Urological Association do not recommend yohimbine as a treatment option for ED (86881).
• Fatigue. Although there is interest in using oral yohimbe for fatigue, there is insufficient reliable information about the clinical effects of yohimbe for this purpose.
• Obesity. Although there is interest in using oral yohimbe for obesity, there is insufficient reliable information about the clinical effects of yohimbe for this condition.
• Orthostatic hypotension. It is unclear if oral yohimbine, a constituent of yohimbe, is beneficial in patients with orthostatic hypotension. Details: Some preliminary clinical research shows that taking a single dose of yohimbine 5.4 mg increases systolic blood pressure and standing diastolic blood pressure in patients with orthostatic hypotension when compared with placebo or pyridostigmine (86811,86890). However, other preliminary clinical research shows that taking yohimbine does not improve blood pressure in patients with orthostatic hypotension due to autonomic failure when compared with placebo (86821). The effect of yohimbe bark has not been investigated in clinical research. More evidence is needed to rate yohimbe for these uses.

(Read more about YOHIMBE)

Some alpha hydroxy acids are used topically, while others are used orally, intravaginally, or by inhalation. See specific monographs for safety information.

PREGNANCY AND LACTATION:
See specific monographs for safety information.

(Read more about ALPHA HYDROXY ACIDS (AHAs))

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). Many of these trials also only included postmenopausal females. 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 and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (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). Many of these trials also only included postmenopausal females. 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 and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (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. Choline is safe in adults when taken in doses below the tolerable upper intake level (UL) of 3.5 grams daily (3094) ...when used intravenously and appropriately. Intravenous choline 1-4 grams daily for up to 24 weeks has been used with apparent safety (5173,5174).

POSSIBLY UNSAFE ...when used orally in doses above the tolerable upper intake level (UL) of 3. 5 grams daily. Higher doses can increase the risk of adverse effects (3094).

CHILDREN: LIKELY SAFE
when used orally and appropriately (3094). Choline is safe in children when taken in doses below the tolerable upper intake level (UL), which is 1 gram daily for children 1-8 years of age, 2 grams daily for children 9-13 years of age, and 3 grams daily for children 14-18 years of age (3094).

CHILDREN: POSSIBLY UNSAFE
when used orally in doses above the UL. High doses can increase the risk of adverse effects (3094).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Choline is safe when taken in doses below the tolerable upper intake level (UL), which is 3 grams daily during pregnancy and lactation in those up to 18 years of age and 3.5 grams daily for those 19 years and older (3094,92114). There is insufficient reliable information available about the safety of choline used in higher doses during pregnancy and lactation.

(Read more about CHOLINE)

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 in amounts commonly found in foods.

POSSIBLY SAFE ...when used orally in medicinal amounts, short-term. GABA has been used with apparent safety in doses of 75 mg to 1.5 grams daily for up to one month in small clinical studies (19361,19363,19369,110134,110135). There is insufficient reliable information available about the safety of GABA when used orally for longer than one month or when used sublingually or intravenously.

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

(Read more about GAMMA-AMINOBUTYRIC ACID (GABA))

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)

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)

POSSIBLY SAFE ...when used orally and appropriately, short-term. L-theanine has been used safely in clinical research in doses of up to 900 mg daily for 8 weeks (12188,36439,96331,96332,96334,96341,97923,101986,104976). There is insufficient reliable information available about the safety of L-theanine when used long-term.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. A specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg twice daily has been used safely in males aged 8-12 years for up to 6 weeks (91744).

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

(Read more about THEANINE)

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)

POSSIBLY UNSAFE ...when used orally. Yohimbine, a constituent of yohimbe, has been associated with serious adverse effects including cardiac arrhythmia, agitation, myocardial infarction, seizure, and others (17465). Some research shows that yohimbine can be safely used under close medical supervision for up to 10 weeks (3305,3307,3311,3313). However, due to safety concerns, yohimbe should not be used without medical supervision.

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally. Yohimbe might have uterine relaxant effects and also cause fetal toxicity (19).

(Read more about YOHIMBE)

(Read more about ALPHA HYDROXY ACIDS (AHAs))

(Read more about BETA-ALANINE)

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).

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 Theoretically, abrupt caffeine withdrawal might increase the levels and adverse effects of lithium.  Details Caffeine has diuretic activity. When abruptly discontinued, it might alter the clearance of lithium (609). There are two case reports of lithium tremor that worsened upon abrupt coffee withdrawal (610).

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.

(Read more about CALCIUM)

ATROPINE Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, choline might decrease the effects of atropine in the brain.  Details Animal research shows that administering choline one hour before administering atropine can attenuate atropine-induced decreases in brain levels of acetylcholine (42240). Theoretically, concomitant use of choline and atropine may decrease the effects of atropine.

(Read more about CHOLINE)

(Read more about CREATINE)

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking GABA with antihypertensive drugs might increase the risk of hypotension.  Details Some clinical research shows that GABA can decrease blood pressure in patients with hypertension (19367).

CNS DEPRESSANTS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, GABA might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.  Details Endogenous GABA has well-established relaxant effects (51152) and GABA(A) receptors have an established physiological role in sleep (51143). However, the effects of GABA supplements are unclear, as it is unknown whether exogenous GABA crosses the blood-brain barrier (51120,51153,90570). Although there have been limited reports of drowsiness or tiredness with GABA supplements (5115,19364), these effects have not been widely reported in clinical studies. Additionally, intravenous GABA 0.1-1 mg/kg has been shown to induce anxiety in a dose-dependent manner (5116).

(Read more about GAMMA-AMINOBUTYRIC ACID (GABA))

ACE INHIBITORS (ACEIs) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use of L-arginine and ACE inhibitors may increase the risk for hypotension and hyperkalemia.  Details Combining L-arginine with some antihypertensive drugs, especially ACE inhibitors, seems to have additive vasodilating and blood pressure-lowering effects (7822,20192,31854,31916). Furthermore, ACE inhibitors can increase potassium levels. Use of L-arginine has been associated with hyperkalemia in some patients (32213,32218). Theoretically, concomitant use of ACE inhibitors with L-arginine may increases the risk of hyperkalemia.

ANGIOTENSIN RECEPTOR BLOCKERS (ARBs) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use of L-arginine and ARBs may increase the risk of hypotension and hyperkalemia.  Details L-arginine increases nitric oxide, which causes vasodilation (7822). Combining L-arginine with ARBs seems to increase L-arginine-induced vasodilation (31854). Furthermore, ARBs can increase potassium levels. Use of L-arginine has been associated with hyperkalemia in some patients (32213,32218). Theoretically, concomitant use of ARBs with L-arginine may increases the risk of hyperkalemia.

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of L-arginine with anticoagulant and antiplatelet drugs might have additive effects and increase the risk of bleeding.  Details Preliminary research suggests that L-arginine infusions reduce platelet aggregation in humans (32260,31864,32239,32220,32257,32263,32276,32188). The clinical significance of this effect is unclear.

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of L-arginine might have additive effects with antidiabetes drugs.  Details Preliminary clinical research shows that L-arginine decreases blood glucose levels in patients with type 2 diabetes (31964,32085,31964,104225).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use of L-arginine and antihypertensive drugs may increase the risk of hypotension.  Details L-arginine increases nitric oxide, which causes vasodilation (7822). Clinical evidence shows that L-arginine can reduce blood pressure in some individuals with hypertension (7818,10636,31871,32201,32167,32225,31923,32232,110383,110384). Furthermore, combining L-arginine with some antihypertensive drugs seems to have additive vasodilating and blood pressure-lowering effects (7822,20192,31854,31916).

ISOPROTERENOL (Isuprel) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, concurrent use of isoproterenol and L-arginine might result in additive effects and hypotension.  Details Preliminary clinical evidence suggests that L-arginine enhances isoproterenol-induced vasodilation in patients with essential hypertension or a family history of essential hypertension (31932).

POTASSIUM-SPARING DIURETICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically concomitant use of potassium-sparing diuretics with L-arginine may increases the risk of hyperkalemia.  Details Potassium-sparing diuretics can increase potassium levels. Use of L-arginine has been associated with hyperkalemia in some patients (32213,32218).

SILDENAFIL (Viagra) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concurrent use of sildenafil and L-arginine might increase the risk for hypotension.  Details In vivo, concurrent use of L-arginine and sildenafil has resulted in increased vasodilation (7822,8015,10636). Theoretically, concurrent use might have additive vasodilatory and hypotensive effects. However, in studies evaluating the combined use of L-arginine and sildenafil for erectile dysfunction, hypotension was not reported (105065).

TESTOSTERONE Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of L-arginine and testosterone might have additive effects.  Details In clinical research, L-arginine increases the level of testosterone in male patients with erectile dysfunction (102586,104222). The clinical significance of this finding is unclear.

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ALCOHOL (Ethanol) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Concomitant use of alcohol and niacin might increase the risk of flushing and hepatotoxicity.  Details Alcohol can exacerbate the flushing and pruritus associated with niacin (4458,11689). Large doses of niacin might also exacerbate liver dysfunction associated with chronic alcohol use. A case report describes delirium and lactic acidosis in a patient taking niacin 3 grams daily who ingested 1 liter of wine (14510). Advise patients to avoid large amounts of alcohol while taking niacin.

ALLOPURINOL (Zyloprim) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as allopurinol.  Details Large doses of niacin can reduce urinary excretion of uric acid, potentially resulting in hyperuricemia (4860,4863,12033). Doses of uricosurics such as allopurinol might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, niacin may have additive effects when used with anticoagulant or antiplatelet drugs.  Details Several cases of clotting factor synthesis deficiency and coagulopathy have been reported in patients taking sustained-release niacin (25915). Also, thrombocytopenia has been reported in patients treated with niacin or niacin plus lovastatin (25916).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.  Details Niacin impairs glucose tolerance in a dose-dependent manner, probably by causing or aggravating insulin resistance and increasing hepatic production of glucose (4860,4863,11692,11693). In diabetes patients, niacin 4.5 grams daily for 5 weeks can increase plasma glucose by an average of 16% and glycated hemoglobin (HbA1c) by 21% (4860). However, lower doses of 1.5 grams daily or less appear to have minimal effects on blood glucose (12033). In some patients, glucose levels increase when niacin is started, but then return to baseline when a stable dose is reached (12033,93344). Up to 35% of patients with diabetes may need adjustments in hypoglycemic therapy when niacin is added (4458,4860,4863,11689,12033).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, niacin may increase the risk of hypotension when used with antihypertensive drugs.  Details The vasodilating effects of niacin can cause hypotension (4863,12033,93341). Furthermore, some clinical evidence suggests that a one-hour infusion of niacin can reduce systolic, diastolic, and mean blood pressure in hypertensive patients. This effect is not observed in normotensive patients (25917).

ASPIRIN Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Likely •  Level of Evidence = B Large doses of aspirin might alter the clearance of niacin.  Details Aspirin is often used with niacin to reduce niacin-induced flushing (4458,11689). Doses of 80-975 mg aspirin have been used, but 325 mg appears to be optimal (4458,4852,4853,11689). Aspirin also seems to reduce the clearance of niacin by competing for glycine conjugation. Taking aspirin 1 gram seems to reduce niacin clearance by 45% (14524). This is probably a dose-related effect and not clinically significant with the more common aspirin dose of 325 mg (11689,14524).

BILE ACID SEQUESTRANTS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Bile acid sequestrants can bind niacin and decrease absorption. Separate administration by 4-6 hours to avoid an interaction.  Details In vitro studies show that colestipol (Colestid) binds about 98% of available niacin and cholestyramine (Questran) binds 10% to 30% (14511).

GEMFIBROZIL (Lopid) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of niacin and gemfibrozil might increase the risk of myopathy in some patients.  Details A case of myopathy from concomitant use of niacin and gemfibrozil has been reported (25920). Niacin alone has also been associated with cases of myopathy (26100,26111). Using gemfibrozil with niacin might further increase the risk of developing myopathy.

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.  Details Niacin has been associated with cases of liver toxicity, especially when used in pharmacologic doses (4863,11689,11691,25929,25930,25931). Sustained-release niacin preparations appear to be associated with a higher risk of hepatotoxicity than immediate-release niacin (11691,25930,25931,93342).

HMG-CoA REDUCTASE INHIBITORS ("Statins") Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of niacin and statins might increase the risk of myopathy and rhabdomyolysis in some patients.  Details Some case reports have raised concerns that niacin might increase the risk of myopathy and rhabdomyolysis when combined with statins (14508,25918). However, a significantly increased risk of myopathy has not been demonstrated in clinical trials, including those using an FDA-approved combination of lovastatin and niacin (Advicor) (7388,11689,12033,14509).

PROBENECID (Benemid) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as probenecid.  Details Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia (4863,12033). Doses of uricosurics such as probenecid might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

SULFINPYRAZONE (Anturane) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as sulfinpyrazone.  Details Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia (4863,12033). Doses of uricosurics such as sulfinpyrazone might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

THYROID HORMONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, niacin might antagonize the therapeutic effects of thyroid hormones.  Details Clinical research and case reports suggests that taking niacin can reduce serum levels of thyroxine-binding globulin by up to 25% and moderately reduce levels of thyroxine (T4) (25916,25925,25926,25928). Patients taking thyroid hormone for hypothyroidism might need dose adjustments when using niacin.

TRANSDERMAL NICOTINE (Nicoderm) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use of niacin and transdermal nicotine might increase the risk of flushing and dizziness.  Details Niacin and nicotine can both cause flushing and dizziness (496,96211).

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CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, theacrine might alter the effects of CNS depressants.  Details Animal research shows that low doses of theacrine have sedating effects, whereas high doses might have stimulant effects (88778). Depending on the dose of theacrine used, it might increase or decrease the effects of CNS depressants. However, these effects have not yet been reported in humans.

(Read more about THEACRINE)

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.  Details Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals (7687,77354). Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

CNS DEPRESSANTS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.  Details Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression (96334). In one clinical study, some subjects taking oral theanine reported drowsiness (96331).

(Read more about THEANINE)

LEVODOPA Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, tyrosine might decrease the effectiveness of levodopa.  Details Tyrosine and levodopa compete for absorption in the proximal duodenum by the large neutral amino acid (LNAA) transport system (2719). Advise patients to separate doses of tyrosine and levodopa by at least 2 hours.

THYROID HORMONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, tyrosine might have additive effects with thyroid hormone medications.  Details Tyrosine is a precursor to thyroxine and might increase levels of thyroid hormones (7212).

(Read more about TYROSINE)

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, combining yohimbe bark with antiplatelet or anticoagulant drugs might have additive effects; however, this has not been reported in clinical research.  Details Research in healthy adults shows that taking yohimbine, a constituent of yohimbe bark, in doses of 8 mg or more, seems to inhibit platelet aggregation in vitro by binding to the alpha-2 adrenoceptor (86773,86806,86835,86853). The effects of yohimbe bark itself are unclear; yohimbe bark contains 0.6% to 1.38% yohimbine, but it is unclear how much is absorbed (86862,89263).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, yohimbe might reduce the effects of antihypertensive drugs.  Details Yohimbine, a constituent of yohimbe, is an alpha-2 adrenoceptor antagonist and has been reported to increase blood pressure in clinical research. Theoretically, concomitant use of yohimbe and antihypertensive drugs can interfere with blood pressure control (11,17465).

CLONIDINE (Catapres) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, yohimbe might precipitate clonidine withdrawal.  Details Chronic clonidine use can downregulate alpha-2 adrenoreceptors. Animal research and one human case report suggest that concomitant administration of yohimbine, an alpha-2 adrenoceptor antagonist, may precipitate clonidine withdrawal and lead to sympathomimetic toxicity, including hypertensive crisis (111406).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, yohimbe might decrease the levels and clinical effects of CYP1A2 substrates.  Details In vitro research shows that yohimbe extract induces CYP1A2 enzymes (111404).

CYTOCHROME P450 2D6 (CYP2D6) INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B CYP2D6 inhibitors may increase the levels and adverse effects of yohimbine, a constituent of yohimbe.  Details In vitro and clinical research shows that the yohimbe bark constituent, yohimbine, is metabolized by CYP2D6 isoenzymes (105688,105697,105698). Paroxetine, a cytochrome P450 (CYP) 2D6 inhibitor, increases the maximum serum concentration of yohimbine and reduces the clearance of yohimbine compared to yohimbine alone in patients who are extensive CYP2D6 metabolizers. (114932).

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, yohimbe might increase the levels and adverse effects of CYP2D6 substrates.  Details In vitro research suggests that yohimbine, a constituent of yohimbe bark, inhibits CYP2D6 enzyme activity (23117).

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, CYP3A4 inhibitors might increase the levels and adverse effects of yohimbine, a constituent of yohimbe bark.  Details In vitro and clinical research shows that the yohimbe bark constituent, yohimbine, is metabolized by CYP3A4 enzymes (105688,105698). Theoretically, drugs that inhibit CYP3A4 might increase the levels and adverse effects of yohimbine.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, yohimbe might decrease the levels and clinical effects of CYP3A4 substrates.  Details In vitro research shows that yohimbe extract induces CYP3A4 enzymes (111404).

MONOAMINE OXIDASE INHIBITORS (MAOIs) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Likely •  Level of Evidence = D Concomitant use of MAOIs with yohimbe can result in additive effects.  Details Yohimbine, a constituent of yohimbe, has MAO inhibitory effects. At high doses, yohimbine is a non-selective inhibitor of MAO (11,12).

PAROXETINE (Paxil) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Paroxetine decreases the clearance of yohimbine and may increase its effects.  Details Paroxetine, a cytochrome P450 (CYP) 2D6 inhibitor, increases the maximum serum concentration of yohimbine by about 350% and reduces the clearance of yohimbine by about 80% compared to yohimbine alone in patients who are extensive CYP2D6 metabolizers. No significant changes in pharmacokinetic parameters of yohimbine were observed with coadministration of paroxetine in patients who are poor CYP2D6 metabolizers (114932).

PHENOTHIAZINES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, using yohimbine with phenothiazines might have additive effects.  Details Yohimbine, a constituent of yohimbe, has alpha-2 adrenergic antagonist effects. Theoretically, combining it with phenothiazines can cause additive alpha-2 adrenergic antagonism (19).

STIMULANT DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking yohimbe with stimulant drugs can have additive effects.  Details Yohimbine, a constituent of yohimbe, has sympathomimetic effects and increases blood pressure in a dose-dependent manner. Theoretically, taking yohimbe with stimulant drugs can have additive stimulant and hypertensive effects (11,12,105698).

TRICYCLIC ANTIDEPRESSANTS (TCAs) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking yohimbe with TCAs can increase adverse effects.  Details A small clinical study in patients taking TCAs for at least 4 weeks shows that receiving doses of intravenous yohimbine 2.5-20 mg daily for up to 7 days precipitates severe anxiety, agitation, and tremor (105881). The effects of yohimbe bark itself are unclear; oral yohimbe bark contains 0.6% to 1.38% yohimbine, but it is unclear how much is absorbed (86862,89263).

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General ...Alpha hydroxy acids represent a group of natural chemicals, some of which can cause adverse effects. See specific monographs for safety information.

(Read more about ALPHA HYDROXY ACIDS (AHAs))

General ...Orally, beta-alanine seems to be generally well tolerated.
Most Common Adverse Effects:
Orally: Flushing, paresthesia.

Gastrointestinal ...While rare, digestion problems have been reported with oral beta-alanine use (94341).

Neurologic/CNS ...Orally, beta-alanine can cause a dose-dependent feeling of pins and needles (paresthesias) along with skin flushing (16438,94333,94335,94338,94341,94342,94349,101028,101029,106711). This generally starts on the scalp within 20 minutes of the dose, spreading to most of the body, and lasting for about an hour. This was described as severe at a dose of 40 mg/kg, tolerable at a dose of 20 mg/kg, and very mild at a dose of 10 mg/kg. At the lowest dose it only occurred in 25% of subjects (16438). In some studies, beta-alanine has been given as frequently as 8 times per day so that each dose can be kept below 10 mg/kg (16438,16439). Other clinical research shows that taking beta-alanine in a tablet formulation eliminates the presence of parasthesias at a dose of 1.6 grams when compared with a solution made from powdered beta-alanine. This effect may be due to delayed absorption (97974,97975). Although paresthesias still occur with sustained-release formulations, their presence is less frequent when compared with immediate-release formulations (101029).

(Read more about BETA-ALANINE)

General ...Caffeine in moderate doses is typically well tolerated.
Most Common Adverse Effects:
Orally: Anxiety, dependence with chronic use, diarrhea, diuresis, gastric irritation, headache, insomnia, muscular tremors, nausea, and restlessness.
Serious Adverse Effects (Rare):
Orally: Stroke has been reported rarely.

Cardiovascular ...Caffeine can temporarily increase blood pressure. Usually, blood pressure increases 30 minutes after ingestion, peaks in 1-2 hours, and remains elevated for over 4 hours (36539,37732,37989,38000,38300).
Although acute administration of caffeine can cause increased blood pressure, regular consumption does not seem to increase either blood pressure or pulse, even in mildly hypertensive patients (1451,1452,2722,38335). However, the form of caffeine may play a role in blood pressure increase after a more sustained caffeine use. In a pooled analysis of clinical trials, coffee intake was not associated with an increase in blood pressure, while ingesting caffeine 410 mg daily for at least 7 days modestly increased blood pressure by an average of 4.16/2.41 mmHg (37657). Another meta-analysis of clinical research shows that taking caffeine increases systolic and diastolic blood pressure by approximately 2 mmHg when compared with control. Preliminary subgroup analyses suggest that caffeine may increase blood pressure more in males or at doses over 400 mg (112738).
When used prior to intensive exercise, caffeine can increase systolic blood pressure by 7-8 mmHg (38308). The blood pressure-raising effects of caffeine are greater during stress (36479,38334) and after caffeine-abstinence of at least 24 hours (38241).
Epidemiological research suggests there is no association of caffeine consumption with incidence of hypertension (38190). Habitual coffee consumption also doesn't seem to be related to hypertension, but habitual consumption of sugared or diet cola is associated with development of hypertension (13739).
Epidemiological research has found that regular caffeine intake of up to 400 mg daily is not associated with increased incidence of atrial fibrillation (38018,38076,91028,91034,97451,97453,103708), atherosclerosis (38033), cardiac ectopy (91127), stroke (37804), ventricular arrhythmia (95948,97453), and cardiovascular disease in general (37805,98806). One clinical trial shows that in adults with diagnosed heart failure, consumption of 500 mg of coffee does not result in an increased risk for arrhythmia during exercise (95950). However, caffeine intake may pose a greater cardiovascular risk to subjects that are not regular users of caffeine. For example, in one population study, caffeinated coffee consumption was associated with an increased risk of ischemic stroke in subjects that don't regularly drink coffee (38102). In a population study in Japanese subjects, caffeine-containing medication use was modestly associated with hemorrhagic stroke in adults that do not consume caffeine regularly (91059).
The most common side effect of caffeine in neonates receiving caffeine for apnea is tachycardia (98807).

Dermatologic ...There are several case reports of urticaria after caffeine ingestion (36546,36448,36475).

Endocrine ...Some evidence shows caffeine is associated with fibrocystic breast disease or breast cancer in females; however, this is controversial since findings are conflicting (8043,108806). Restricting caffeine in females with fibrocystic breast conditions doesn't seem to affect breast nodularity, swelling, or pain (8996). A population analysis of the Women's Health Initiative observational study has found no association between consumption of caffeine-containing beverages and the incidence of invasive breast cancer in models adjusted for demographic, lifestyle, and reproductive factors (108806). Also, a dose-response analysis of 2 low-quality observational studies has found that high consumption of caffeine is not associated with an increased risk of breast cancer (108807).
Clinical research in healthy adults shows that an increase consumption of caffeine results in increased insulin resistance (91023).

Gastrointestinal ...Gastrointestinal upset, nausea, diarrhea, abdominal pain, and fecal incontinence may occur with caffeine intake (36466,37755,37806,37789,37830,38138,38136,38223,95956,95963). Also, caffeine may cause feeding intolerance and gastrointestinal irritation in infants (6023). Perioperative caffeine during cardiopulmonary bypass surgery seems to increase the rate of postoperative nausea and vomiting (97451). Caffeine and coffee consumption have been associated with an increase in the incidence of heartburn (37545,37575,38251,38259,38267) and gastrointestinal esophageal reflux disease (GERD) (38329,37633,37631,37603).

Genitourinary ...Caffeine, a known diuretic, may increase voiding, give a sense of urgency, and irritate the bladder (37874,37961,104580). In men with lower urinary tract symptoms, caffeine intake increased the risk of interstitial cystitis/painful bladder syndrome (38115). Excessive caffeine consumption may worsen premenstrual syndrome. Consumption of up to 10 cups of caffeinated drinks daily was associated with increased severity of premenstrual syndrome (38177). Finally, population research shows that exposure to caffeine was not associated with an increased risk of endometriosis (91035).

Immunologic ...Caffeine can cause anaphylaxis in sensitive individuals, although true IgE-mediated caffeine allergy seems to be relatively rare (11315).

Musculoskeletal ...Caffeine can induce or exacerbate muscular tremors (38136,37673,38161). There has also been a report of severe rhabdomyolysis in a healthy 40-year-old patient who consumed an energy drink containing 400 mg of caffeine (4 mg/kg) and then participated in strenuous weightlifting exercise (108818).
Epidemiological evidence regarding the relationship between caffeine use and the risk for osteoporosis is contradictory. Caffeine can release calcium from storage sites and increase its urinary excretion (2669,10202,11317,111489). Females with a genetic variant of the vitamin D receptor appear to be at an increased risk for the detrimental effect of caffeine on bone mass (2669). However, moderate caffeine intake, less than 300 mg daily, does not seem to significantly increase osteoporosis risk in most postmenopausal adults with normal calcium intake (2669,6025,10202,11317). Premature infants treated with intravenous caffeine for apnea of prematurity, have a lower bone mineral content compared with infants who are not treated with caffeine, especially when treatment extends beyond 14 days (111489).

Neurologic/CNS ...Caffeine can cause headaches, anxiety, jitteriness, restlessness, and nervousness (36466,37694,37755,37806,37865,37830,37889,38223,95952). In adolescents, there is an inverse correlation between the consumption of caffeine and various measurements of cognitive function (104579). Insomnia is a frequent adverse effect in children (10755). Caffeine may result in insomnia and sleep disturbances in adults as well (36445,36483,36512,36531,37598,37795,37819,37862,37864,37890)(37968,37971,38091,38242,91022,92952). Additionally, caffeine may exacerbate sleep disturbances in patients with acquired immunodeficiency syndrome (AIDS) (10204). Combining ephedra with caffeine can increase the risk of adverse effects. Jitteriness, hypertension, seizures, temporary loss of consciousness, and hospitalization requiring life support has been associated with the combined use of ephedra and caffeine (2729). Finally, epidemiological research suggests that consuming more than 190 mg of caffeine daily is associated with an earlier onset of Huntington disease by 3.6 years (91078).

Ocular/Otic ...In individuals with glaucoma, coffee consumption and caffeine intake has been found to increase intraocular pressure (8540,36464,36465,37670). The magnitude of this effect seems to depend on individual tolerance to caffeine. Some research in healthy young adults shows that caffeine increases intraocular pressure to a greater degree in low-consumers of caffeine (i.e., 1 cup of coffee or less daily) when compared to high-consumers (i.e., those consuming 2 cups of coffee or more daily) (100371). The peak increase of intraocular pressure seems to occur at about 1.5 hours after caffeine ingestion, and there is no notable effect 4 hours after ingestion (36462,100371).

Oncologic ...Most human studies which have examined caffeine or methylxanthine intake have found that they do not play a role in the development of various cancers, including breast, ovarian, brain, colon, rectal, or bladder cancer (37641,37737,37775,37900,38050,38169,38220,91054,91076,108806).

Psychiatric ...Caffeine may lead to habituation and physical dependence (36355,36453,36512,36599), with amounts as low as 100 mg daily (36355,36453). An estimated 9% to 30% of caffeine consumers could be considered addicted to caffeine (36355). Higher doses of caffeine have caused nervousness, agitation, anxiety, irritability, delirium, depression, sleep disturbances, impaired attention, manic behavior, psychosis and panic attacks (36505,37717,37818,37839,37857,37982,38004,38017,38028,38072)(38079,38138,38306,38325,38331,38332,97464). Similar symptoms have been reported in a caffeine-naïve individual experiencing fatigue and dehydration after a dose of only 200 mg, with resolution of symptoms occurring within 2 hours (95952).
Withdrawal: The existence or clinical importance of caffeine withdrawal is controversial. Some researchers think that if it exists, it appears to be of little clinical significance (11839). Headache is the most common symptom, due to cerebral vasodilation and increased blood flow (37769,37991,37998). Other researchers suggest symptoms such as tiredness and fatigue, decreased energy, alertness and attentiveness, drowsiness, decreased contentedness, depressed mood, difficulty concentration, irritability, and lack of clear-headedness are typical of caffeine withdrawal (13738). Withdrawal symptoms typically occur 12-24 hours after the last dose of caffeine and peak around 48 hours (37769,36600). Symptoms may persist for 2-9 days. Withdrawal symptoms such as delirium, nausea, vomiting, rhinorrhea, nervousness, restlessness, anxiety, muscle tension, muscle pains, and flushed face have been described. However, these symptoms may be from nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839). In a case report, caffeine consumption of 560 mg daily was associated with increased suicidality (91082).

Renal ...Data on the relationship between caffeine intake and kidney stones are conflicting. Some clinical research shows that caffeine consumption may increase the risk of stone formation (37634,111498), while other research shows a reduced risk with increasing caffeine intakes (111498). A meta-analysis of 7 studies found that overall, there is an inverse relationship, with a 32% decrease in the risk of kidney stones between the lowest and highest daily intakes of caffeine (111498).

Other ...People with voice disorders, singers, and other voice professionals are often advised against the use of caffeine; however, this recommendation has been based on anecdotal evidence. One small exploratory study suggests that caffeine ingestion may adversely affect subjective voice quality, although there appears to be significant intra-individual variability. Further study is necessary to confirm these preliminary findings (2724).

(Read more about CAFFEINE)

General ...Orally and intravenously, calcium is well-tolerated when used appropriately.
Most Common Adverse Effects:
Orally: Belching, constipation, diarrhea, flatulence, and stomach upset.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about calciphylaxis and kidney stones.

Cardiovascular ...There has 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 results, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). 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 CVD, CHD, or MI (93533,107231). Also, the association between calcium supplementation and CVD, CHD, or 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). To minimize the possible risk of CVD, CHD, or MI, advise patients not to consume more than the recommended daily intake of 1000-1200 mg and to consider total calcium intake from both dietary and supplemental sources (17484). While dietary intake of calcium is preferred over supplemental intake, advise patients who require calcium supplements to take calcium along with vitamin D, as this combination does not appear to be associated with an increased risk of MI (93533).
Rarely, calcium intake can increase the risk of calciphylaxis, which usually occurs in patients with kidney failure. Calciphylaxis is the deposition of calcium phosphate in arterioles, which causes skin ulcers and skin necrosis. In a case report, a 64-year-old female with a history of neck fracture, sepsis, and ischemic colitis presented with painful leg ulcers due to calciphylaxis. She discontinued calcium and vitamin D supplementation and was treated with sodium thiosulfate and supportive care (95816).

Gastrointestinal ...Orally, calcium can cause belching, flatulence, nausea, gastrointestinal discomfort, and diarrhea (1824,1843,12950,38803). Although constipation is frequently cited as an adverse effect of calcium, there is no scientific substantiation of this side effect (1824,1843,1844,1845,12950,38978). Calcium carbonate has been reported to cause acid rebound, but this is controversial (12935,12936).

Oncologic ...There is some concern that very high doses of calcium might increase the risk of prostate cancer. Some epidemiological evidence suggests that consuming over 2000 mg/day of dietary calcium might increase the risk for prostate cancer (4825,12949). Additional research suggests that calcium intake over 1500 mg/day might increase the risk of advanced prostate cancer and prostate cancer mortality (14132). Consumption of dairy products has also been weakly linked to a small increase in prostate cancer risk (98894). However, contradictory research suggests no association between dietary intake of calcium and overall prostate cancer risk (14131,14132,104630). More evidence is needed to determine the effect of calcium, if any, on prostate cancer risk.

Renal ...Kidney stones have been reported in individuals taking calcium carbonate 1500 mg daily in combination with vitamin D 2000 IU daily for 4 years (93943).

(Read more about CALCIUM)

General ...Orally, choline is well tolerated when used appropriately. Adverse effects have been reported with doses exceeding the tolerable upper intake level (UL) of 3.5 grams daily.
Most Common Adverse Effects:
Orally: Fishy body odor. At high doses of at least 9 grams daily, choline has been reported to cause diarrhea, nausea, salivation, sweating, and vomiting.

Cardiovascular ...Orally, doses of choline greater than 7. 5 grams daily may cause low blood pressure (94648).

Gastrointestinal ...Orally, large doses of choline can cause nausea, vomiting, salivation, and anorexia (42275,91231). Gastrointestinal discomfort has reportedly occurred with doses of 9 grams daily, while gastroenteritis has reportedly occurred with doses of 32 grams daily (42291,42310). Doses of lecithin 100 grams standardized to 3.5% choline have reportedly caused diarrhea and fecal incontinence (42312).

Genitourinary ...Orally, large doses of choline greater than 9 grams daily have been reported to cause urinary incontinence (42291).

Neurologic/CNS ...Orally, high intake of choline may cause sweating due to peripheral cholinergic effects (42275).

Oncologic ...In one population study, consuming large amounts of choline was associated with an increased risk of colorectal cancer in females, even after adjusting for red meat intake (14845). However, more research is needed to confirm this finding.

Psychiatric ...Orally, large doses of choline (9 grams daily) have been associated with onset of depression in patients taking neuroleptics. Further research is needed to clarify this finding (42270).

Other ...Orally, choline intake may cause a fishy body odor due to intestinal metabolism of choline to trimethylamine (42285,42275,42310,92111,92112).

(Read more about CHOLINE)

General ...Orally, creatine is generally well-tolerated. Topically, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Dehydration, diarrhea, gastrointestinal upset, muscle cramps, and water retention.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about interstitial nephritis, renal insufficiency, rhabdomyolysis, and venous thrombosis.

Cardiovascular ...Some research suggests that creatine supplementation can cause edema. In a randomized controlled trial, 26% of patients with amyotrophic lateral sclerosis (ALS) receiving creatine 10 grams daily reported edema after 2 months of treatment compared to 9% with placebo. The difference between groups was statistically significant at 2 months but not at month 4 and beyond. Creatine is believed to cause slight water retention, which may have been more apparent in patients who were immobilized due to ALS (46647). While this adverse drug reaction did not lead to worsening cardiac function in these patients, theoretically, creatine-related water retention could worsen congestive heart failure or hypertension.
There is one case report of lone atrial fibrillation in a 30-year-old male vegetarian. He started powdered creatine 20 grams daily for 5 days, followed by 2.5 grams daily for a month. However, he discontinued powdered creatine due to severe cramping and diarrhea, and reinitiated creatine supplementation a month later with an encapsulated formulation. Aside from gelatin in the capsule, creatine was the only ingredient listed in both formulations. During the loading dose phase, the patient developed dyspnea and palpitations and was diagnosed with lone atrial fibrillation in the emergency department. Symptoms resolved with treatment and supplement discontinuation (13187). Theoretically, alterations in electrolyte balance due to dehydration or diarrhea could lead to conduction abnormalities and arrhythmia; however, in this case, the patient had normal electrolyte levels. Contaminants in dietary supplements might also be responsible for adverse reactions; this specific creatine product was not tested for contaminants. It remains unclear whether creatine was associated with this event.
Theoretically, taking creatine nitrate might reduce blood pressure and heart rate due to its nitrate component. However, clinical research shows that creatine nitrate 12 grams daily for 7 days followed by 3 grams daily for 21 days does not lower blood pressure or heart rate acutely or chronically when compared to creatine monohydrate or placebo (95959).

Dermatologic ...In a small clinical trial of older, healthy males, one subject out of the 10 receiving creatine 5 grams four times daily for 10 days followed by 4 grams daily for 20 days reported a skin rash during the study. The type and severity of rash and whether it resolved after creatine was discontinued were not discussed (4572). Also, skin rash has been reported by patients taking celecoxib and creatine; however, whether this effect was due to creatine or celecoxib is unclear (46706).
Topically, burning, itching, redness, irritation, and perception of changes in skin temperature have been reported (104669).

Endocrine ...Creatine may influence insulin production (11330). In human research, insulin levels increased 120 and 240 minutes after creatine supplementation (46760); however, there was no effect in another trial (46732). In a clinical study, 0.3 grams/kg of creatine daily for one week significantly increased cortisol levels by 29%. However, the levels returned to baseline at week 2 (46615).

Gastrointestinal ...Some small clinical studies have reported diarrhea and vomiting with oral creatine supplementation (4584,11332,46562,46684,46698,46704,104673). Also, gastrointestinal distress, transient abdominal discomfort, constipation, heartburn, and nausea have been reported by a small number of individuals in randomized, controlled clinical trials (4572,11332,46527,46528,46573,46589,46622,46668,46684,46695), (46704,46771,95964,104668,104669,104673,108316). However, most high-quality clinical research shows that creatine does not increase the incidence of gastrointestinal upset (103102,103278,103279).
Undissolved creatine powder may cause gastroenteritis (1368). Additionally, simultaneous intake of creatine and caffeine powder may increase the occurrence of gastrointestinal distress (95964).

Hematologic ...There are two case reports of creatine-related venous thrombosis in otherwise healthy adults. In the first case, an active 18-year-old male who had been taking an unspecified dose of creatine daily for 3 months was diagnosed with venous thrombosis via MRI. The patient reported increased thirst and fluid consumption when taking creatine. In the second case, an active 31-year-old male who had recently taken a 5-hour flight was diagnosed with deep vein thrombosis. He had been taking an unspecified dose of creatine. After stopping creatine and receiving anticoagulation therapy for 6 months, both patients' thromboses were resolved and did not recur. Researchers speculate that dehydration might be to blame for these adverse events, as dehydration increases the risk of thrombosis. In both cases, thrombophilic conditions were ruled out, and a temporal relationship between creatine consumption and thrombosis was established (90301). However, it remains unclear if creatine was responsible for these thrombotic events.

Hepatic ...Despite two case reports describing hepatic injury in patients taking creatine (46701,90319), meta-analyses and clinical studies specifically evaluating the safety of creatine have not identified an increased risk for hepatic injury (103278,103279). In addition, population research suggests that there is not an association between creatine intake and liver fibrosis, cirrhosis, or hepatic steatosis. However, this study largely included subjects consuming less than 4 grams daily (112208).
One preliminary clinical trial specifically evaluated the effect of creatine loading and maintenance doses on hepatic function indices in healthy adults. No clinically significant changes in hepatic indices were reported in patients taking creatine loading doses of 20 grams daily for 5 days followed by maintenance doses of 3 grams daily for 8 weeks (46521). Another clinical study evaluated the impact of creatine monohydrate and creatine nitrate on liver function enzymes, showing no change in levels within 5 hours after the first dose of 12 grams or after continued consumption of 12 grams daily for 7 days followed by 3 grams daily for 21 days (95959). The patients that experienced hepatic injury in the available case reports were also taking other exercise supplements. Whether the reported adverse hepatic effects were due to creatine or the other supplements patients were taking is unclear. Also, neither of these case reports addressed whether the supplements were tested for contamination (46701,90319).

Musculoskeletal ...Creatine-associated increase in body mass is well documented in randomized, controlled clinical trials and is often as large as 1-2 kg during the five-day loading period of creatine (2101,4569,4589,4591,4600,4605,46504,46561,46815,46827)(46830,46843,95962,103279,112201). This may be considered an unwanted adverse reaction in some individuals and a desired effect of supplementation in others. This weight gain may interfere with mass-dependent activities such as running and swimming (46504,46823). Muscle cramping due to creatine supplementation has been reported in controlled clinical trials and may result from water retention in skeletal muscle (2104,4572,4584,30915,46562,46695,46826,46827,104673). However, most high quality clinical research shows that creatine does not increase the incidence of musculoskeletal injuries or muscle cramping (103102). In one case report, rhabdomyolysis in a weight lifter using creatine 25 grams daily over a one-year period has been reported (12820). Another case report describes an adult male who developed acute compartment syndrome of the leg after regular consumption of an unspecified amount of creatine and cocaine (112210).

Neurologic/CNS ...In clinical research, thirst, sleepiness, mild headache, and syncope have been reported for patients taking creatine, although the events were uncommon (46578,46615,46820). More serious adverse events have been reported for patients taking creatine in combination with other ingredients. A case of ischemic stroke has been reported for an athlete who consumed creatine monohydrate 6 grams, caffeine 400-600 mg, ephedra 40-60 mg, and a variety of other supplements daily for 6 weeks (1275). In another case, a 26 year old male reported with a hemorrhagic stroke linked to taking the supplement Jack3d, which contains creatine, DMAA, schizandrol A, caffeine, beta-alanine, and L-arginine alpha-ketoglutarate (90318). It is likely that these adverse events were due to other ingredients, such as caffeine, ephedra, and DMAA, which are known to have stimulant and vasoconstrictive properties.

Oncologic ...Population research shows that use of muscle building supplements such as creatine, protein, and androstenedione is associated with an increased odds of testicular germ cell cancer. This risk appears to be more apparent in early users, those using two or more muscle building supplements, and those with long-term use of the supplements. The odds of testicular germ cell cancer may be increased by up to 155% in males taking both creatine and protein supplements (90329). The risk of testicular germ cell cancer from creatine alone is unclear from this study.

Psychiatric ...Anxiety, irritability, depression, aggression, and nervousness have been reported in clinical research for patients taking creatine, although the effects are not common (46518). A case of acute organic psychosis was reported in a 32-year-old soldier in Iraq who was consuming excessive amounts of caffeine coupled with use of creatine (Creatamax, MaxiNutrition) one tablet twice daily for 3 weeks plus a specific stimulant containing bitter orange, guarana seed extract, and St. John's wort extract (Ripped Fuel Ephedra Free, Twinlabs) two tablets three times daily for 2 days prior to admission. The psychosis was considered likely due to caffeine consumption in combination with the stimulant supplement rather than creatine (37982).

Renal ...Isolated cases of renal dysfunction in patients taking creatine have been reported, including a case of interstitial nephritis in a healthy male (184) and a case of renal insufficiency in a football player (46828). In contrast to these cases, several clinical studies and case reports have shown that creatine does not affect markers of renal function in healthy adults (2120,3996,4573,16535,46735,46749,46758,46779,46813,95959,103279). Doses studied included 5- to 7-day loading regimens of 12 to 21 grams daily (2120,46813), or maintenance doses of 3-10 grams daily for up to 2 years (16535,46712,46758,95959). In two additional studies, creatine supplementation 15.75 grams for 5 days followed by 4.25 grams daily for 20 days with carbohydrate and protein ingestion led to no change of renal stress markers (46844). Other clinical research has shown that ingestion of creatine up to 30 grams daily for 5 years is not associated with an increased incidence of renal dysfunction (103102).
Other case reports involve patients with pre-existing renal dysfunction. For example, in one case, a patient with a history of recurrent renal failure developed relapsing steroid-responsive nephritis syndrome after taking creatine (1368,2118). In another case, a patient with diabetic nephropathy who was taking creatine and metformin developed severe metabolic acidosis and acute renal failure. It is unclear if creatine contributed to this event, as metformin alone is known to cause metabolic acidosis (46738). These case reports have raised concern that individuals with pre-existing renal dysfunction may be at increased risk for renal injury with creatine supplementation. However, no prospective clinical trials have been conducted in this population to clarify this concern.
In addition, two cases of acute kidney injury and hypercalcemia have been reported in 16 year old males that took 1-4 servings of creatine for less than 4 weeks; however, the creatine product contained unlabeled, very high doses of vitamin D, which is the likely cause of these symptoms (109739).
In one survey, 13% of male collegiate athletes taking creatine reported dehydration (4584). The Association of Professional Team Physicians has warned that creatine may cause dehydration, heat-related illnesses, and electrolyte imbalances, and reduce blood volume. Mild transient dehydration resulting in an elevated serum creatinine was also reported in a single person in a clinical trial (104672). However, a study found that creatine supplementation during preseason football training had no effect on fluid or electrolyte status (46845). Additionally, most high quality clinical research shows that creatine does not increase dehydration (103102). A theoretical increase in risk of dehydration due to intracellular fluid shifts has led most creatine manufacturers to caution about adequate hydration with creatine supplementation (4576).

Other ...There have been reports of heat intolerance with oral creatine supplementation (46505). Increases in formaldehyde production have been reported with creatine use. A-24 year-old man taking supratherapeutic doses of creatine monophosphate in combination with an energy supplement developed malignant hyperthermia after undergoing anesthesia. His symptoms included tachycardia, hypertension, hypercarbia, and hyperthermia. Environmental factors are suspected to have played a role in the development of malignant hyperthermia, so whether this adverse event was due to creatine at all is unclear (46717).
In 1997, three collegiate wrestlers died after engaging in a rapid weight-loss program in order to qualify for competition (93628). Initially creatine supplementation was considered to have contributed to or caused these deaths (12820,93629); however, investigations by the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) did not confirm this belief (12820,93630). It appears that only one of the three wrestlers had been using creatine. Instead, the deaths were related to drastic, short-term weight loss in which the wrestlers wore rubber suits, avoided hydration, and performed workouts in rooms with temperatures up to 33 °C (1368,93631).

(Read more about CREATINE)

General ...Orally, GABA seems to be generally well tolerated. Sublingually, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Drowsiness, gastric upset, minor throat burning, muscle weakness, and nausea.

Cardiovascular ...Intravenously, GABA can cause dose-related increases in blood pressure and pulse (5116).

Gastrointestinal ...Orally, minor throat burning has been associated with GABA in one study (5115). In another study in which GABA was administered with phosphatidylserine, one patient experienced severe gastric distress, two patients reported moderate nausea, and one reported constipation (19364). Children with cerebral palsy taking GABA experienced nausea and decreased appetite (19362).

Genitourinary ...In one study, one patient treated with oral GABA and phosphatidylserine reported transient amenorrhea (19364).

Musculoskeletal ...Orally, minor adverse effects associated with GABA included muscle weakness (5115).

Neurologic/CNS ...Orally, GABA may cause drowsiness, headache, or tiredness (5115,19364,112830). Four children with cerebral palsy taking GABA had convulsions, and an unspecified number experienced motor restlessness. However, causality of these adverse effects was not clear, and the dose of GABA was not specified (19362). Intravenously, GABA 50 mg has been associated with a "lack of alertness" in healthy female volunteers (51159).

Psychiatric ...Intravenously, GABA 0. 1-1.0 mg/kg has been shown to induce anxiety, dysphoria, and mood disturbances in a dose-dependent manner (5116).

Other ...In one study, patients taking GABA experienced a slight warming of the body (19370).

(Read more about GAMMA-AMINOBUTYRIC ACID (GABA))

General ...Oral, intravenous, and topical L-arginine are generally well tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, bloating, nausea, diarrhea, headache, insomnia, flushing.
Intravenously: Excessively rapid infusion can cause flushing, headache, nausea and vomiting, numbness, and venous irritation.

Cardiovascular ...L-arginine taken orally by pregnant patients in a nutrition bar containing other antioxidants was associated with a 36% greater risk of palpitations when compared with a placebo bar (91197). It is unclear if this effect was due to L-arginine, other ingredients, or other factors.

Dermatologic ...Orally, arginine can cause flushing, rash, and hives (3460,32138,102587,104223). The skin reactions were likely of allergic etiology as oral L-arginine has been associated with eosinophilia (32138). In one case report, intravenous administration caused allergic reactions including urticaria, periorbital edema, and pruritus (11830). Excessively rapid infusion of L-arginine has caused flushing, local venous irritation, numbness. Extravasation has caused necrosis and superficial phlebitis (3330,16817).

Gastrointestinal ...Orally, L-arginine has been reported to cause nausea, diarrhea, vomiting, dyspepsia, gastrointestinal discomfort, and bloating (1363,31855,31871,31972,31978,32261,90198,91197,96811,99243)(102587,102592).
Orally, L-arginine has been reported to cause esophagitis in at least six adolescents. Symptoms, which included pain and dysphagia, occurred within 1-3 months of treatment in most cases (102588). There are at least two cases of acute pancreatitis possibly associated with oral L-arginine. In one case, a 28-year-old male developed pancreatitis after consuming a shake containing 1.2 grams of L-arginine daily as arginine alpha-ketoglutarate. The shake also contained plant extracts, caffeine, vitamins, and other amino acids. Although there is a known relationship between L-arginine and pancreatitis in animal models, it is not clear if L-arginine was directly responsible for the occurrence of pancreatitis in this case (99266).
Intravenously, excessively rapid infusion of L-arginine has been reported to cause nausea and vomiting (3330,16817).

Musculoskeletal ...Intravenous L-arginine has been associated with lower back pain and leg restlessness (32273). Orally, L-arginine has been associated with asthenia (32138).

Neurologic/CNS ...Orally, L-arginine has been associated with headache (31855,31955,32261,91197,102587,102592), insomnia, fatigue (102587,102592), and vertigo (32150,102592).

Oncologic ...In breast cancer patients, L-arginine stimulated tumor protein synthesis, which suggests stimulated tumor growth (31917).