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POSSIBLY EFFECTIVE

• Alzheimer disease. Oral alpha-GPC, taken alone or in combination with donepezil, may be beneficial for improving cognitive function in patients with Alzheimer disease. Details: A meta-analysis of 3 moderate-sized clinical studies in patients with Alzheimer disease shows that taking alpha-GPC 1200 mg daily for up to 6 months improves cognitive function as measured using the Mini-Mental State Examination (MMSE) when compared with placebo. Additionally, an analysis of 4 different clinical trials in patients with Alzheimer disease shows that taking alpha-GPC 1200 mg with donepezil 10 mg daily for up to 2 years improves cognitive function as measured using the MMSE and Alzheimer's Disease Assessment Scale - cognition subscale (ADAS-Cog) and may decrease behavioral symptoms and improve functional abilities when compared with donepezil alone (111731).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Brain tumor. It is unclear if oral alpha-GPC is beneficial in patients with brain tumors. Details: Observational research in patients being treated for glioblastoma suggests that taking alpha-GPC, around 400 mg 2-3 times daily, for 12 months or longer is associated with a 14-month-increase in overall survival but no improvement in progression-free survival when compared with patients not taking alpha-GPC (111732). The validity of these findings is limited by the retrospective nature of the study.
• Cognitive function. Although there has been interest in using oral alpha-GPC to improve cognitive function in healthy adults, there is insufficient reliable information about the clinical effects of alpha-GPC for this purpose.
• Stroke. It is unclear if intramuscular or oral alpha-GPC is beneficial for preventing stroke or improving post-stroke outcomes. Details: A large, open-label, uncontrolled clinical trial in patients who experienced a stroke or transient ischemic attack within the past 10 days shows that intramuscular administration of alpha-GPC 1200 mg daily for 28 days, followed by 400 mg three times daily by mouth for 6 months, modestly improves cognitive and behavioral function when compared to baseline (12102). The validity of this finding is limited by the lack of a comparator group. While this evidence suggests that alpha-GPC may offer some benefit in patients recovering from stroke, observational research in healthy individuals aged 50 years and older has found that alpha-GPC use is associated with a 43% greater risk of stroke, including a 34% greater risk of ischemic stroke and a 37% greater risk of hemorrhagic stroke, when compared with non-users at 10-years' follow-up. Additionally, alpha-GPC use for 2-6 months, 6-12 months, or greater than 12 months is associated with a greater risk of stroke when compared with alpha-GPC use for less than 2 months, suggesting that the increase in stroke risk may be dependent on the total dose received or duration of exposure (108883).
• Vascular dementia. It is unclear if intramuscular alpha-GPC is beneficial in patients with vascular dementia. Details: A small, open-label study in adults with mild to moderate vascular dementia shows that intramuscular administration of a prescription-only formulation of alpha-GPC (Delecit; not available in the US) 1000 mg daily for 90 days improves cognitive function, behavior, mood, and functionality similarly to cytosine diphosphocholine (CDP) 1 gram daily (12101). It is not clear how these improvements compare with standard care. More evidence is needed to rate alpha-GPC for these uses.

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EFFECTIVE

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

LIKELY EFFECTIVE

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

POSSIBLY EFFECTIVE

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

POSSIBLY INEFFECTIVE

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

INSUFFICIENT RELIABLE EVIDENCE to RATE

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

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LIKELY EFFECTIVE

• Mental alertness. Consumption of caffeinated coffee attenuates changes in alertness and cognitive capacity that occur throughout the day. It also improves mental performance and alertness following sleep deprivation. Details: Consumption of coffee and other caffeinated beverages seems to prevent a decline in alertness and cognitive capacity when consumed throughout the day (4221,4224). Caffeine can improve mental performance and alertness following prolonged sleep deprivation (10205). With respect to mental alertness while driving, some research shows that drinking a single cup of coffee containing 80 mg caffeine in 180 mL during a 15-minute rest after simulated driving for 2 hours reduces the amount of weaving and increases speed consistency in the 3rd and 4th hours of driving when compared with drinking decaffeinated coffee. Overall, the mental effort needed to drive, driving quality, and feelings of sleepiness appear to improve with caffeine consumption (93875).

POSSIBLY EFFECTIVE

• Diabetes. Population research has found that consumption of caffeinated coffee is associated with a reduced risk of developing type 2 diabetes. Consumption of coffee also seems to be associated with a reduced risk of mortality in patients with type 2 diabetes. Details: Population research suggests that consumption of caffeinated coffee is associated with a dose-dependent reduced risk of developing type 2 diabetes (11353,11731,14313,38174,91040,91055,111040). Some research suggests that increasing coffee consumption by 1 cup daily is associated with a 6% to 9% reduction in the incidence of type 2 diabetes (91040,91055). In North American adults, consuming 6 or more cups of coffee daily is associated with a 29% lower risk of developing diabetes in females and a 54% lower risk in males (11353). Research in European adults suggests that drinking 5-6 cups of coffee daily appears to reduce diabetes risk by 61% in females and 30% in males. Drinking 10 or more cups daily reduces diabetes risk by 79% in females and 55% in males (11731). Additional research suggests that drinking 3-4 cups of coffee daily reduces the risk of diabetes by 23% to 42% when compared with drinking just 1 cup daily (14343,38174). An analysis of these and other cohort studies involving over 457,000 patients suggests that drinking 3-4 cups of coffee or decaffeinated coffee daily is associated with a 25% to 35% reduced risk of type 2 diabetes when compared with drinking 2 cups or less daily. Each additional cup of coffee consumed each day is associated with a 5% to 10% reduction in the incidence of type 2 diabetes (97368). Some population research in patients with previous gestational diabetes has also investigated the association between consumption of coffee and risk of developing type 2 diabetes. Research suggests that consumption of at least 4 cups of caffeinated coffee daily is associated with a 54% reduced risk of type 2 diabetes when compared with drinking no coffee. There is no association between consumption of decaffeinated coffee and type 2 diabetes risk (111040). Coffee consumption has also been evaluated in patients with type 2 diabetes, with mixed findings. Most population research suggests that coffee consumption is associated with a reduced risk of mortality in patients with type 2 diabetes. In one meta-analysis of observational studies, drinking high amounts of coffee was associated with a 24% reduction in mortality risk, with a 9% reduction for each additional cup of coffee (104595). In another meta-analysis, drinking up to 4 cups of coffee daily was associated with a 19% reduction in all-cause mortality and a 34% reduction in coronary heart disease (CHD) mortality when compared with not drinking coffee. Reductions in cardiovascular disease (CVD) mortality were only significant when one large study was excluded during sensitivity analyses (107836). Results of individual studies are conflicting (37805,97374,104589,104594). Additionally, a cross-sectional study in older adults with type 2 diabetes has examined the relationship between coffee consumption and CVD risk factors. This study suggests that higher coffee consumption is associated with lower fasting plasma glucose and diastolic blood pressure and higher high-density lipoprotein (HDL) cholesterol and triglyceride levels (107825). Population research has examined the relationship between coffee consumption and change in kidney function in patients with type 2 diabetes. One study in patients with normal kidney function suggests that drinking any coffee is associated with up to a 25% prevention in kidney function decline when compared with no coffee consumption. Kidney function decline was based on estimated glomerular function rate (eGFR) measurements (111043).
• Heart failure. Consumption of caffeinated coffee seems to reduce the long-term risk of heart failure in those without cardiovascular disease (CVD) at baseline. Details: A meta-analysis of three large population studies, the Framingham Heart Study (FHS), Cardiovascular Heart Study (CHS), and Atherosclerosis Risk in Communities (ARIC) study, has found that increased daily coffee consumption is associated with a reduced long-term risk of heart failure in individuals without CVD at baseline. Drinking at least 2 cups of coffee daily is associated with a 29% to 31% reduced risk of heart failure. In the analysis, total caffeine intake, but not decaffeinated coffee intake, was associated with a reduced risk of heart failure (104597).
• Overall mortality. Consumption of coffee seems to reduce all-cause mortality. The effects of coffee on specific causes of mortality are variable. Details: Population research conducted in almost 4 million international individuals suggests that long-term, daily consumption of coffee is associated with an 8% to 28% reduction in all-cause mortality when compared to low or no coffee consumption (97373,97374,103997,103998,104594,104595,105308,105311,105314,107826)(107833,107839,111033), though not all research agrees (107822). The strongest association is seen for individuals consuming 2-4 cups of coffee daily and in never smokers. Most research suggests that consuming ground, instant, or decaffeinated coffee is associated with similar reductions in mortality (97373,97374,103997,103998,104594,104595,105308,105311,105314,107833)(111033). The use of sweeteners might affect the association of coffee consumption with all-cause mortality. Population research suggests that consumption of unsweetened coffee, in amounts ranging from any to up to 4.5 cups daily depending on type of coffee, is associated with a reduction in mortality of 14% to 39% when compared with no coffee consumption. Consumption of 1.5 to 3.5 cups of sugar-sweetened coffee is associated with a reduction in mortality of approximately 30%; however, this association does not occur with higher coffee intakes or the consumption of decaffeinated coffee. Any association between the consumption of artificially sweetened coffee and mortality is unclear. When subgroup analyses were conducted to determine the association of coffee consumption with cause-specific mortality, coffee consumption was associated with a reduction in cardiovascular mortality. In some analyses, this association is for ground or decaffeinated, but not sweetened, instant, or unfiltered, coffee (97373,97374,103997,103998,104594,104595,105308,105311,105314,107833)(111032). In another analysis, consumption of coffee was inversely associated with deaths from chronic respiratory diseases, diabetes, pneumonia and influenza, and intentional self-harm. There were no associations between coffee consumption and deaths from accidents, Alzheimer disease, or kidney disease (105311). The association between coffee consumption and cancer-related mortality is less clear. Although one large meta-analysis of population research suggests that consumption of approximately 2 cups of coffee daily is associated with a 4% decrease in cancer-related mortality, the results of individual studies are mixed. One large population cohort suggests that ground or instant caffeinated coffee consumption is associated with up to a 27% reduction in cancer mortality (97374), while other analyses show no association (97373,103994,105308,105311,107822). The reasons for this discrepancy are not clear but may be related to smoking status or use of sweeteners. In one meta-analysis, consumption of each additional cup of coffee daily is associated with a 2% decrease in cancer-related mortality in non-smokers, as opposed to an increased risk in smokers (105308). Other population research suggests that only intake of unsweetened coffee, and not sugar-or artificially-sweetened coffee, is associated with a reduced risk of cancer-related mortality (111032).
• Parkinson disease. Consumption of coffee seems to reduce the risk of developing Parkinson disease. This effect seems to be dose related in males, but not in females. Details: There is evidence that the risk of Parkinson disease is lower in people who consume caffeinated beverages such as coffee, tea, and cola. For males, the effect seems to be dose related. Males consuming the greatest amount of caffeinated coffee, 28 ounces (three to four cups) or a total of 421-2716 mg of caffeine from any source daily, seem to have the greatest reduction in risk. However, a significant reduction in risk exists even with consumption of as little as approximately 1-2 cups of coffee, or 124-208 mg of caffeine, daily (6022). In females, the effect does not seem to be dose related. Moderate consumption of caffeinated coffee, 1-3 cups daily, provides the greatest reduction in risk (1238). Coffee does not appear to provide additional protection from Parkinson disease in cigarette smokers (9236).
• Postoperative ileus. Consumption of coffee seems to decrease the time to first stool and first flatus, and possibly time to discharge, after gynecological or colorectal surgeries. Details: Meta-analyses of mainly small clinical trials in patients who have undergone gynecological or colorectal surgeries show that drinking coffee decreases the time to the first stool and time to tolerating solid food by about 10-15 hours when compared with no treatment or drinking water or tea (103991,111035,112732). Although one meta-analysis found that drinking coffee does not reduce the length of hospital stay (103991), other research shows that hospital stay is reduced by up to 1.5 days; however, the validity of these results are limited by high heterogeneity. In addition, sub-analyses suggest that benefit is limited to gynecological surgery and not colorectal surgery or caesarian section (97386,111035,112732). Sub-analyses also suggest that drinking coffee does not improve bowel function after caesarian section (103991,111035). Caffeinated coffee has been most commonly consumed as 100 mL three times daily starting after surgery and until the first stool. Some studies have used decaffeinated coffee (93876,97386,103991,111035,111039).

POSSIBLY INEFFECTIVE

• Esophageal cancer. Consumption of coffee does not seem to be associated with a reduced risk of esophageal cancer. Details: Population research has found that coffee intake is not associated with the incidence of esophageal cancer (9222,90186,100874). However, subgroup analyses have found coffee consumption may be associated with a reduced risk of esophageal cancer in patients from East Asia (100874).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in consuming coffee for ADHD, there is insufficient reliable information about the clinical effects of coffee for this purpose.
• Atherosclerosis. It is unclear if consuming coffee is beneficial for atherosclerosis. Details: Population research has found that drinking coffee is not associated with prevalent coronary-artery calcium, a subclinical marker of atherosclerosis, in patients without known coronary heart disease (97371).
• Atrial fibrillation. It is unclear if consuming coffee affects the risk of atrial fibrillation. The available research is conflicting. Details: A meta-analysis of observational research suggests that coffee intake is not associated with the incidence of atrial fibrillation (100860). However, a more recent observational study suggests that drinking at least 1 cup of coffee per week is associated with a 40% increased risk of atrial fibrillation, with the highest incidence of atrial fibrillation occurring in adults consuming at least 6 cups daily. A sub-analysis found that this association remained only for White participants and not other ethnicities (111042). This study was limited by its relatively small sample size and a higher than general proportion of smokers. Some observational research in elderly persons following the Mediterranean diet suggests that consuming 4-28 cups of coffee monthly (up to 1 cup daily) is associated with a lower risk of atrial fibrillation when compared with 3 cups or less monthly. Consuming more than 1 cup of coffee daily was not associated with reduced risk (103988). However, it is unclear if this association was due to moderate coffee consumption, the Mediterranean diet, or other, unidentified factors.
• Bladder cancer. Population research suggests that coffee consumption does not reduce the risk of bladder cancer. Details: Although earlier evidence has been conflicting (97375,97376), the most comprehensive analysis of cohort and case control studies has found that coffee consumption is not associated with bladder cancer risk. In subgroup analyses of females, males, or non-smokers, coffee did not affect risk (103992).
• Brain tumor. It is unclear if consuming coffee reduces the risk of brain cancer. Details: Observational research has found that consumption of coffee is associated with a lower risk of brain cancer in Asian populations, but not in American populations (100870).
• Breast cancer. Population research suggests that coffee consumption does not reduce the risk of breast cancer. Details: Population research has found that consumption of coffee is not associated with a reduced incidence of breast cancer (9235,97377,107823).
• Cancer. Although there has been interest in using rectal coffee enemas for the treatment of cancer, there is insufficient reliable information about the clinical effects of coffee for this purpose.
• Cardiovascular disease (CVD). Some population research has found that drinking coffee is associated with a reduced risk of heart failure, but not with a reduced risk of major adverse cardiac events, coronary heart disease, or CVD in general. In patients with a history of CVD, coffee consumption may reduce CVD-related mortality. However, at least some evidence suggests that there is a J-shaped association between coffee consumption and the risk of acute coronary syndromes. Details: A meta-analysis of three large population studies, the Framingham Heart Study (FHS), Cardiovascular Heart Study (CHS), and Atherosclerosis Risk in Communities (ARIC) study, suggests that increased daily coffee consumption is associated with a reduced long-term risk of heart failure in individuals without CVD at baseline. Drinking at least 2 cups of coffee daily is associated with a 29% to 31% reduced risk of heart failure. However, there was no association between coffee consumption and risk of stroke, coronary heart disease, or CVD in general. In the analysis, total caffeine intake, but not decaffeinated coffee intake, was associated with a reduced risk of heart failure (104597). In one cohort study, there was no association between past coffee-drinking and the prevalence of having coronary heart disease as determined by a coronary angiography (104588). However, a large population study suggests that drinking up to 5 cups daily of instant, ground, or decaffeinated coffee is associated with a reduced risk of incident CVD, including coronary heart disease, cardiac failure, and/or ischemic stroke, of approximately 11% (111033). The association between coffee consumption and arrhythmia has also been investigated. In one population study, there was a 3% reduced risk of arrhythmia for each additional cup of habitual coffee consumed. Similar effects were seen when atrial fibrillation and supraventricular tachycardia, but not ventricular tachycardia, were independently analyzed (105310). More recent population research suggests that consuming 1-5 cups daily of ground or instant coffee, but not decaffeinated coffee, is associated with up to a 17% reduced risk of arrhythmia when compared with not consuming coffee. Intake of more than 5 cups was no longer associated with a reduced risk of arrhythmia (111033). Some population research suggests a J-shaped association between regular coffee consumption and the risk of developing acute coronary syndromes. Moderate consumption of less than 300 mL daily (about 1.3 cups) was associated with a lower risk of developing acute coronary syndromes, whereas regular consumption of 300 mL daily or more was associated with an increased risk (11318). However, other population research in people without a history of CVD suggests that drinking more than 6 cups of coffee daily does not appear to be associated with an increased risk of developing coronary heart disease (14343). The association between coffee consumption and CVD-related mortality has also been evaluated in people with CVD. Population research suggests that coffee consumption is associated with a reduction in CVD-related mortality. In some analyses, this association is for ground or decaffeinated coffee only (97373,97374,103997,103998,104594,104595,105308,105311,105314). A meta-analysis of a small number of population studies suggests that consuming coffee for at least 1 year after a myocardial infarction (MI) is associated with a small reduction in risk of CVD-related mortality and no increased risk of all-cause mortality or major cardiac events, such as a recurrent MI or stroke (104882). In patients with a history of acute coronary syndrome, including acute MI or unstable angina, consumption of 1-3 cups of coffee daily is associated with a reduced risk of overall mortality over a 4-year period, especially in never or former smokers. However, in those who are current smokers, consuming more than 3 cups daily is associated with a more than 2-fold increased risk of overall mortality (8533,105313). A large observational study which followed patients with stable coronary artery disease for 5 years also suggests that there is no association between coffee consumption and CVD-related mortality, myocardial infarction, or stroke (112735).
• Chronic kidney disease (CKD). It is unclear if consuming coffee is beneficial for the prevention or management of CKD. Details: A small meta-analysis of population research has found that coffee consumption is associated with a 14% reduced incidence of CKD; drinking at least 2 cups daily seems to have the most benefit. Coffee consumption is also associated with an 18% reduced incidence of progression to kidney failure, as well as lower odds of having albuminuria. In addition, coffee consumption is associated with a reduced risk of CKD-related death, with at least 4 cups daily providing the most benefit when compared with drinking no coffee (104586). The validity of these findings is limited by the heterogeneous definitions of CKD, kidney failure, and albuminuria in the individual studies, as well as the comparisons of coffee consumption.
• Cognitive function. It is unclear if consuming coffee is beneficial for cognitive function. Details: Some population research has found that higher lifetime coffee consumption might positively affect cognitive function among females aged 80 years or older (10620). Additionally, a small clinical study in healthy adults shows that consuming a single dose of regular coffee 220 mL containing 100 mg of caffeine improves reaction time and working memory, but not episodic memory, when compared with placebo (100864).
• Colorectal cancer. It is unclear if consuming coffee is beneficial for the prevention or treatment of colorectal cancer. Details: A meta-analysis of cohort studies conducted in North America and Europe suggests that there is no association between coffee intake and the incidence of colorectal cancer (97385). However, population research conducted in Japan and Korea suggests that drinking coffee is associated with a lower risk of colorectal cancer, with the greatest reduction seen in patients consuming 3 or more cups of coffee daily (9222,97384,107832,111041). In one study, risk reduction increased from 32% to 78% when adjusted for the use of coffee additives, including cream and sugar (107832). In addition, drinking coffee is associated with a reduced risk of disease progression and death in patients with advanced or metastatic colorectal cancer. Each additional cup daily is associated with a 5% reduced risk of cancer progression and a 7% reduced risk of death. The greatest benefits were associated with drinking at least 4 cups daily when compared with no coffee consumption (104591).
• Constipation. Although there has been interest in consuming coffee for constipation, there is insufficient reliable information about the clinical effects of coffee for this purpose.
• Dementia. It is unclear if consuming coffee is beneficial for preventing dementia. Details: One meta-analysis of observational studies including nearly 329,000 adults has found that drinking coffee is not associated with a lower risk of dementia or Alzheimer disease (100866). Conversely, other observational research has found evidence of benefit, but results are conflicting. A meta-analysis of observational studies in nearly 334,000 adults has found a reduced risk of any cognitive deficit (including mild cognitive impairment and dementia) or dementia alone in those drinking less than 2.8 or 2.3 cups of coffee daily, respectively, when compared with not drinking coffee (107829). The validity of these findings is limited by a lack of discussion of heterogeneity and variability in sensitivity analyses. An individual observational study in nearly 14,000 adults has found that coffee and caffeine consumption is associated with dose-dependent reductions in dementia risk, especially in males, and that drinking at least 3 cups of coffee daily is associated with a 50% lower risk of dementia when compared with not drinking coffee (107841). Coffee consumption has also been studied in combination with tea. An observational study has found that drinking 0.5-1 cup of coffee with at least 4 cups of tea or 2-3 cups of coffee and tea each daily is associated with a 28% to 30% reduced risk of dementia when compared with not drinking coffee and tea (107204).
• Depression. It is unclear if consuming coffee is beneficial for reducing the risk of depression. Details: Observational research has found that higher coffee consumption is associated with a 24% lower risk of depression when compared with lower coffee consumption. Drinking 400-600 mL of coffee daily is associated with 16% lower risk of depression when compared with not consuming coffee (100863).
• Endometrial cancer. It is unclear if consuming coffee is beneficial for the prevention of endometrial cancer; the available research is conflicting. Details: One meta-analysis of prospective cohort studies suggests that drinking coffee is associated with a dose-dependent reduction in the risk of endometrial cancer. Increasing coffee consumption by 4 cups daily is associated with a 20% reduction in endometrial cancer risk (97381). Another meta-analysis of population research suggests that the highest intake of caffeinated coffee, but not decaffeinated coffee, is associated with a 34% reduced risk of endometrial cancer when compared with the lowest. A sub-analysis suggests that this association is limited to individuals with a high body mass index (111036). In contrast, earlier meta-analyses and one large prospective cohort study conducted in the United Kingdom suggests that drinking coffee is not associated with a reduced risk of endometrial cancer in general; however, there may be some protection in obese females drinking at least 2 cups of caffeinated coffee daily (93873,97381,97382).
• Fractures. It is unclear if consuming coffee is beneficial for fracture prevention. Details: Multiple meta-analyses of observational research suggest that the highest intake of coffee is not associated with a difference in the odds of fracture when compared with the lowest intake. However, any association may be dependent on the dose of coffee and/or the location of research (111034,112734). A dose-response analysis in one meta-analysis suggests that consuming 0.5 to 4 cups daily, but not higher amounts, is associated with a small reduction in the incidence of hip fracture when compared with no coffee consumption. Additional sub-analyses suggest that while the highest coffee consumption was associated with a 25% reduced risk of fracture in studies conducted in Europe and North America, the opposite is true in studies conducted in Asia where the risk is increased by 37% (111034).
• Gallbladder disease. Population research suggests that consuming coffee may reduce the risk of developing symptomatic gallstone disease. Details: Population research has found that the consumption of caffeinated beverages, including coffee, that provide at least 400 mg of caffeine (two or more cups of coffee) daily 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 (four or more cups of coffee) daily is associated with the greatest reduction in risk (3345).
• Gastric cancer. It is unclear if consuming coffee reduces the risk of gastric cancer. Details: Overall, meta-analyses of observational research suggest that coffee consumption does not affect gastric cancer risk. However, subgroup analyses of patients living in the United States suggest that consuming coffee is associated with an increased risk of gastric cancer (100873,111038). One sub-analysis suggests that consuming 6.5 or more cups of coffee daily was associated with a 36% greater risk of gastric cancer (100873).
• Gout. It is unclear if consuming coffee is beneficial for preventing gout. Details: Epidemiological research has found that the risk of developing gout over a 12-year period is 40% lower in males aged 40-75 years who drink 4-5 cups of caffeinated coffee daily, compared with those who don't drink coffee. In people who drink 6 cups or more daily, the risk of developing gout is 59% lower. Drinking decaffeinated coffee is also associated with a reduced risk of developing gout, but the risk reduction is more modest than with caffeinated coffee (15540).
• Headache. Although caffeine is an established treatment for certain types of headache, there is insufficient reliable information about the clinical effects of coffee, specifically, for this purpose.
• Hearing loss. It is unclear if consuming coffee is beneficial for hearing loss. Details: Population research has found that consuming at least one cup of coffee daily is associated with a reduced risk of hearing impairment in males, but not females, when compared with less than one cup of coffee daily. In males, each additional cup consumed daily was associated with a 15% lower risk of hearing impairment (104592).
• Hepatitis B. It is unclear if consuming coffee is beneficial for hepatitis B. Details: Population research in patients being treated for chronic hepatitis B suggests that drinking at least 3 cups of coffee a day is associated with a reduced risk of having liver fibrosis when compared to not consuming coffee. However, this association was not present in untreated patients (111044). This study is limited by its cross-sectional design and use of blood markers, rather than the gold standard liver biopsy, for diagnosing fibrosis.
• Hyperlipidemia. It is unclear if consuming caffeinated coffee is beneficial for hyperlipidemia. Details: A meta-analysis of small, randomized, controlled trials shows that consuming caffeinated coffee for up to about 11 weeks reduces total cholesterol by 8 mg/dL, low-density lipoprotein (LDL) cholesterol by 5 mg/dL, and triglycerides by 13 mg/dL when compared with a control group. These effects appear to be dose-dependent, with the greatest reduction observed in individuals consuming 6-8 cups of coffee daily. Every additional cup of caffeinated coffee consumed daily is associated with a 3-4 mg/dL additional reduction in total and LDL cholesterol and a 6-7 mg/dL additional reduction in triglyceride levels. Decaffeinated coffee had no effect on any markers of cholesterol (97370). However, population research has found that coffee consumption is associated with slightly higher total cholesterol, LDL cholesterol, and triglyceride levels when compared with no coffee consumption (104590).
• Hypertension. Epidemiologic research suggests that consuming coffee reduces the risk of developing hypertension. Details: Some epidemiological research suggests that coffee consumption might reduce the risk of developing hypertension. A meta-analysis of epidemiologic research suggests that long-term coffee intake is associated with a modest 9% reduction in the risk of developing hypertension. However, smoking may diminish any potential benefit (97372). This analysis did not investigate the likelihood of a dose-response relationship and did not adjust for smoking status. Another epidemiologic study in a Brazilian population that did adjust for sociodemographic factors such as smoking suggests that drinking 1-3 cups of coffee daily is associated with a reduced risk of hypertension by about 18% when compared with never or almost never drinking coffee. Drinking more than 3 cups of coffee did not impact risk (103993). However, this study defined 1 cup of coffee as 50 mL; it is unclear how this intake compares with typical use in other countries. The best evidence comes from a meta-analysis of observational research which suggests that coffee intake was not associated with hypertension risk. However, coffee intake was associated with a modest reduction in hypertension risk in studies conducted in the United States (111037). In patients with hypertension, a meta-analysis of epidemiologic research suggests that habitual coffee intake is not associated with the risk of developing CVD (105312). However, other prospective population research in patients with severe hypertension, but not mild hypertension, suggests that drinking at least two cups of coffee daily is associated with a 2-fold increase in CVD mortality compared with non-coffee drinkers (111027).
• Hypotension. It is unclear if consuming caffeinated coffee is beneficial in older adults with postprandial hypotension. Details: Preliminary clinical research in older adults with postprandial hypotension shows that consuming caffeinated beverages like coffee seems to increase blood pressure (11835).
• Irritable bowel syndrome (IBS). It is unclear if consuming coffee is beneficial for preventing IBS. Details: A meta-analysis of mostly small, low-quality, observational and population research suggests that coffee consumption is associated with a modestly lower odds of developing IBS when compared with no coffee consumption. However, the validity of this result is limited by high heterogeneity (112739).
• Kidney failure. It is unclear if consuming coffee is beneficial for preventing progression to kidney failure or reducing the risk of chronic kidney disease (CKD)-related death. Details: A small meta-analysis of population research has found that coffee consumption is associated with an 18% reduced incidence of progression from CKD to kidney failure. Coffee consumption is also associated with a reduced risk of CKD-related death, with at least 4 cups daily providing the most benefit when compared with not drinking coffee (104586). This analysis is limited by the heterogeneous definitions of CKD and kidney failure in the individual studies, as well as the comparisons of coffee consumption.
• Liver cancer. It is unclear if consuming coffee reduces the risk of liver cancer. Details: A meta-analysis of observational research in approximately 2.5 million adults in Asia, North America, and Europe suggests that consuming at least 1 cup of coffee daily is associated with a 27% to 48% reduced risk of liver cancer (111016). An earlier meta-analysis of observational research suggests that regular coffee consumption is associated with a 31% lower risk of hepatocellular carcinoma when compared with no consumption. Higher coffee consumption seems to have a greater preventative effect when compared with lower coffee consumption (103989).
• Liver disease. It is unclear if consuming coffee reduces the risk of chronic liver disease. Details: Observational research has found that regular coffee consumption is associated with a 38% lower risk of chronic liver disease when compared with no consumption. Higher coffee consumption seems to have a greater preventative effect when compared with lower coffee consumption (100862).
• Lung cancer. It is unclear if consuming caffeinated coffee reduces the risk of lung cancer; the available research is conflicting. Details: Epidemiological research has found that males who consume a higher amount of dietary phytoestrogens, such as the lignan precursors found in coffee and tea, have up to a 27% lower risk of developing lung cancer when compared with those who consume smaller amounts (13190). However, conflicting evidence suggests that people who consume 2-4 or more cups of caffeinated coffee daily have a significantly increased risk of developing lung cancer (13191,90177). But drinking decaffeinated coffee seems to be associated with a decreased risk of lung cancer (13191).
• Melanoma. It is unclear if consuming coffee reduces the risk of malignant melanoma. Details: Population research has found that high coffee intake is associated with a 19% to 25% reduction in the risk of malignant melanoma when compared with low consumption. However, after adjusting for confounders, most data show no significant reduction. Drinking decaffeinated coffee is not associated with a reduced incidence of malignant melanoma (97378,97379).
• Metabolic syndrome. It unclear if consuming decaffeinated coffee is beneficial in patients with metabolic syndrome. Details: A meta-analysis of mostly small randomized controlled studies in patients with metabolic syndrome shows that consumption of decaffeinated coffee modestly reduces systolic and diastolic blood pressure when compared with control. The validity of these findings is limited by the high heterogeneity and small size of the included studies (107830).
• Nonalcoholic fatty liver disease (NAFLD). Observational research suggests that consuming coffee may reduce the risk of NAFLD. Observational and clinical research on liver fibrosis is conflicting. Details: A meta-analysis of observational research in over 50,000 patients has found that drinking 1-2 cups of coffee daily does not affect NAFLD incidence when compared with drinking less than 1 cup of coffee. However, drinking more than 3 cups of coffee daily was associated with a reduced risk of NAFLD when compared with less than 2 cups daily (103990). Other observational research has found a reduced risk of NAFLD and/or fibrosis in those who drink coffee when compared with those who do not drink coffee (100872,107831). However, the validity of these findings is limited by a relatively small population size and the lack of dose-response analyses. Two of the primary bioactive constituents of coffee, caffeine and chlorogenic acid, also have been evaluated. A small study in patients with NAFLD and type 2 diabetes shows that taking caffeine 200 mg and/or chlorogenic acid 200 mg for 6 months has no effect on the reduction of hepatic fat and fibrosis when compared with placebo (107835).
• Nonmelanoma skin cancer. It is unclear if consuming caffeinated coffee reduces the risk of nonmelanoma skin cancer. Details: Population research has found that the highest intake of coffee or caffeine is associated with an 18% reduction in nonmelanoma skin cancer risk when compared with the lowest intake. However, the benefit appears to be limited to the incidence of basal cell carcinoma. Drinking decaffeinated coffee is not associated with a reduced incidence of nonmelanoma skin cancer. The effect, if any, appears to be due to caffeine rather than coffee (97380).
• Obesity. It is unclear if consuming coffee is beneficial for weight loss in patients who are overweight or obese; the available research is conflicting. Details: Some clinical research in males who are overweight or obese and are receiving dietary counseling shows that taking coffee mannooligosaccharides 2 grams twice daily for 12 weeks reduces body weight by 6%, compared with 2.3% with placebo. The product also reduces body fat in males, but not females (93877). Additional clinical research in patients with pre-obesity shows that drinking a dark roast coffee 500 mL daily, enriched with N-methylpyridinium ions, for 4 weeks results in weight loss of 3.5%, compared with 0% with a light roast coffee enriched in chlorogenic acids. The dark roast coffee appears to reduce caloric intake (93874). However, other clinical research in adults who are overweight or obese shows that drinking caffeinated or decaffeinated coffee 885 mL daily for 8 weeks does not appear to improve glycemic control or reduce weight (93879).
• Osteoporosis. It is unclear if consuming coffee is beneficial for osteoporosis prevention. Details: A meta-analysis of observational research suggests that the highest coffee consumption is associated with a 21% reduced odds of osteoporosis when compared with the lowest (111034).
• Pancreatitis. It is unclear if consuming coffee reduces the risk of pancreatitis. Details: Observational research has found that drinking three or more cups of coffee daily is associated with a 22% lower risk of pancreatitis when compared with drinking less coffee (100871).
• Pharyngeal cancer. It is unclear if consuming coffee reduces the risk of pharyngeal cancer. Details: Observational research has found that high coffee consumption is associated with a 28% reduced odds of pharyngeal cancer when compared with low coffee consumption (100869).
• Pregnancy-induced hypertension. It is unclear if consuming coffee reduces the risk of pregnancy-induced hypertension. Details: A large prospective cohort study in pregnant patients in Japan has found that the highest total caffeine intake is associated with a 26% increased risk of pregnancy-induced hypertension when compared with no intake, but that a higher coffee intake (at least 2 cups daily) is associated with a 21% reduced risk of pregnancy-induced hypertension when compared with no intake, even when adjusted for total caffeine intake (107827). The validity of these findings may be limited by the fact that detailed information on proteinuria and hypertension were unavailable.
• Pneumonia. It is unclear if consuming coffee is beneficial for reducing the risk of pneumonia. Details: A case-control study in elderly patients has found a 50% reduced risk of pneumonia in those consuming 2 or more cups of coffee daily over the past month (107840). The validity of this finding may be limited by differences in the baseline characteristics between the matched control subjects and the cases, specifically the higher prevalence of hypertension and diabetes in the control group.
• Prostate cancer. Population research has found that coffee consumption is associated with a modestly reduced risk of prostate cancer. Details: Although some individual studies disagree (107834), population research has found that the highest coffee consumption is associated with a small reduction in the risk of prostate cancer when compared with the lowest consumption (97383,97384,104587). Sub-analyses show that coffee consumption is associated with a 7% reduced risk of localized, but not advanced or fatal, prostate cancer (97383,97384,104587).
• Stroke. It is unclear if coffee consumption, alone or in combination with tea, is beneficial for stroke, post-stroke dementia, all-cause mortality, or stroke-related mortality. The available research is conflicting. Details: Several meta-analyses of population research in patients with and without cardiovascular disease (CVD) have found no association between coffee consumption and risk of stroke (104597,104882). However, another meta-analysis of population research and an individual observational study have found that coffee consumption (e.g., 2-3 cups of coffee daily) is associated with an 8% to 12% reduced risk of stroke, especially ischemic stroke, when compared with no consumption (107204,107828). The validity of the findings from the meta-analysis is limited by the lack of a dose-response analysis. Additionally, this analysis found that consumption of 2-3 cups of coffee daily is associated with a 20% reduced risk of post-stroke dementia when compared with not drinking coffee (107204). The consumption of coffee in combination with tea has also been evaluated. An observational study has found that consumption of 2-3 cups daily each of coffee and tea, including black tea, is associated with a 32% reduced risk of stroke when compared with not drinking coffee and tea. Additionally, consumption of 0.5-1 cup of coffee and 2-3 cups of tea, including black tea, daily is associated with a 50% reduced risk of post-stroke dementia when compared with not drinking coffee and tea (107204). Coffee consumption has also been evaluated for its effects on stroke-related and all-cause mortality. One observational study has found that consumption of 1-2 cups of coffee daily is associated with a 50% reduced risk of stroke-related mortality (107822). However, another observational study in patients with a history of stroke has found no association between coffee consumption and all-cause mortality (107839).
• Thyroid cancer. It is unclear if consuming coffee reduces the risk of thyroid cancer. Details: Population research has found that high coffee consumption is associated with a 25% lower risk of thyroid cancer when compared with low consumption. Every additional cup of coffee was associated with a 5% reduction in risk (103996). More evidence is needed to rate coffee for these uses.

(Read more about COFFEE)

LIKELY EFFECTIVE

• Cystic fibrosis. Long-term nebulized hypertonic sodium chloride improves lung function and reduces pulmonary exacerbations in patients with cystic fibrosis. Details: Meta-analyses of clinical research in adults with cystic fibrosis show that, when taken along with a bronchodilator and other standard therapies, nebulized hypertonic sodium chloride in concentrations of 3% to 7%, up to 10 mL twice daily for 4 weeks, increases forced expiratory volume at one second (FEV1) when compared with isotonic saline (sodium chloride 0.9%) (26230,26230). This benefit was not seen at 48 weeks. Other clinical research in adults with cystic fibrosis shows that inhaling sodium chloride 7%, 4 mL twice daily for 48 weeks, does not improve FEV1 when compared with isotonic saline. However, chronic treatment with hypertonic saline does reduce the number of pulmonary exacerbations and increase the number of patients without pulmonary exacerbations when compared with isotonic saline (29402). It is not clear if this benefit occurs in children with cystic fibrosis. The Pulmonary Clinical Practice Guidelines Committee of the Cystic Fibrosis Foundation recommends that individuals with cystic fibrosis aged 6 years or older use nebulized hypertonic saline long-term to improve lung function, reduce the number of exacerbations, and improve quality of life (29403).

POSSIBLY EFFECTIVE

• Amphotericin B nephrotoxicity. Oral sodium chloride seems to prevent nephrotoxicity associated with use of amphotericin B. Details: Clinical research shows that administering oral or intravenous sodium chloride 150 mEq daily during treatment with amphotericin B can attenuate the rise in serum creatinine levels and preserve renal function when compared to treatment with amphotericin B alone (26226).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Bipolar disorder. It is unclear if oral sodium is beneficial in preventing lithium level fluctuations in patients with bipolar disorder. Details: A moderate-sized open-label clinical study in adults with type I bipolar disorder receiving lithium carbonate shows that taking sodium chloride 1 gram daily for 12 weeks along with dietary salt restriction of 1 gram daily reduces the percentage of patients with lithium level fluctuations above 0.8 mEq/L, but does not significantly affect serum sodium, potassium, aldosterone, or creatinine levels when compared with controls who were not salt restricted, but were advised not to consume additional salt at the table (112909). However, the interpretation of these findings is limited by missing data in both groups.
• Canker sores. Although there is interest in using topical sodium chloride for canker sores, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Congestive heart failure. It is unclear if oral sodium is beneficial in patients with acute decompensated heart failure requiring decongestive therapy with diuretics. Details: A moderate-sized clinical study in adults hospitalized with acute decompensated heart failure requiring high-dose intravenous furosemide shows that taking sodium chloride 2 grams three times daily for up to 96 hours does not affect patient weight or serum creatinine levels when compared with placebo (112911). However, the clinical relevance of this study is unclear and it may have been inadequately powered to detect a difference between groups.
• Conjunctivitis. Although there is interest in using ophthalmic sodium chloride for conjunctivitis, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Hyponatremia. Although there is interest in using oral sodium chloride for hyponatremia, there is insufficient reliable information about the clinical effects of oral sodium chloride for this condition.
• Pharyngitis. Although there is interest in using topical sodium chloride for pharyngitis, there is insufficient reliable information about the clinical effects of sodium chloride for this condition.
• Prematurity. It is unclear if oral sodium is beneficial for premature infants. Details: Preliminary clinical research in infants born at less than 32 weeks' gestation shows that adding sodium 4 mEq/kg daily to enteral feedings, starting from the 7th day after birth and continuing through the 35th day, reduces the risk of developing hyponatremia and improves weight gain when compared with adding water (98180). A small, open-label clinical study in newborns less than 35 weeks gestation shows that high sodium intake, defined as an average of 0.25% sodium in maintenance fluids, for 48 hours on day 2 and 3 after birth results in less weight loss within the first 72 hours of life when compared with control, but does not improve mortality, length of hospital stay, or complications from prematurity (112908). However, interpretation of these findings is limited by varied concentrations of sodium as an intervention. More evidence is needed to rate sodium for these uses.

(Read more about SODIUM)

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)

POSSIBLY SAFE ...when used orally and appropriately. Alpha-GPC has been used with apparent safety at doses of 400 mg three times daily (1200 mg/day) for up to 6 months (12102,12176). ...when used intramuscularly and appropriately. Alpha-GPC has been administered intramuscularly with apparent safety at doses of 1000-1200 mg/day for 28 to 90 days (12100,12102).

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

(Read more about ALPHA-GPC)

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 and appropriately. Drinking decaffeinated coffee or coffee containing caffeine in low to moderate amounts is safe (15,98806). According to a review by Health Canada, and a subsequent large meta-analysis conducted in the US, drinking up to 4 cups of coffee daily providing caffeine 400 mg daily is 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 beverages such as coffee that contain caffeine 400 mg daily is not associated with increased risk of major chronic diseases, such as cardiovascular disease or cancer, in healthy adults (98806).

POSSIBLY UNSAFE ...when used orally in excessive amounts. Acute use of high doses of caffeine (more than 400 mg per day), which is found in more than 4 cups of caffeinated coffee, has been associated with significant adverse effects such as tachyarrhythmia and sleep disturbances (11832). Drinking caffeinated coffee in amounts greater than 6 cups per day (about 600 mg caffeine) short-term or long-term can also cause caffeinism, with symptoms of anxiety possibly progressing to delirium and agitation. Chronic use of caffeine, especially in large amounts, can sometimes produce tolerance, habituation, and psychological dependence (3719). Abrupt discontinuance of caffeine can cause physical withdrawal symptoms (11733). Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine found in ingredients such as coffee, which naturally contains caffeine, does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product. ...when used rectally as an enema. Coffee enemas have been linked to cases of severe electrolyte abnormalities and septicemia leading to severe side effects including death (3026,3347,3349,6652).

CHILDREN: POSSIBLY SAFE
when coffee containing caffeine is consumed orally in moderate amounts. Oral intake of caffeine in doses of less than 2.5 mg/kg daily is not associated with significant adverse effects in children and adolescents (11733,98806). However, higher doses should be avoided. The adverse effects typically associated with caffeine-containing coffee are usually more severe in children than adults (11733).

PREGNANCY: POSSIBLY SAFE
when used orally in moderate amounts. Intake of caffeine from coffee and other sources should be monitored during pregnancy. Caffeine crosses the human placenta, but is not considered a teratogen. 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 (2708,2709,2710,2711,9606,11733,16014,16015). However, some research has also found that intrauterine exposure to even modest amounts of caffeine, based on maternal blood levels during the first trimester, is associated with a shorter stature in children ages 4-8 years (109846). In some studies, consuming amounts over 200 mg daily has been associated with a significantly increased risk of miscarriage (16014). This increased risk may be most likely to occur in people 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, most healthy pregnant patients can safely consume caffeine in doses up to 300 mg daily without an increased risk of spontaneous abortion, stillbirth, preterm birth, fetal growth retardation, or congenital malformations (11733,98806). 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. Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine found in ingredients such as coffee, which naturally contains caffeine, does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product.

PREGNANCY: POSSIBLY UNSAFE
when caffeinated coffee providing more than 300 mg of caffeine daily is consumed orally. Caffeine from coffee crosses the placenta, producing fetal blood concentrations similar to maternal levels (4260). 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 from all sources below 300 mg daily during pregnancy. This is similar to the amount of caffeine in about 3 cups of coffee. 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). Drinking more than 6 cups of coffee daily increases the risk of spontaneous abortion (2709). Drinking 8 or more cups of coffee daily doubles the risk of stillbirth when compared with those who do not drink coffee during pregnancy (10621).

LACTATION: POSSIBLY SAFE
when used orally. Drinking one or two caffeine-containing beverages daily during lactation is not associated with unacceptable levels of caffeine in human milk (11734).

LACTATION: POSSIBLY UNSAFE
when used orally in large amounts. Caffeine from coffee can cause wakefulness or irritability in breast-fed infants. Caffeine can also cause feeding intolerance and gastrointestinal irritation in infants (6026).

(Read more about COFFEE)

LIKELY SAFE ...when used orally and appropriately. Sodium is safe in amounts that do not exceed the Chronic Disease Risk Reduction (CDRR) intake level of 2.3 grams daily (100310). Higher doses can be safely used therapeutically with appropriate medical monitoring (26226,26227).

POSSIBLY UNSAFE ...when used orally in high doses. Tell patients to avoid exceeding the CDRR intake level of 2.3 grams daily (100310). Higher intake can cause hypertension and increase the risk of cardiovascular disease (26229,98176,98177,98178,98181,98183,98184,100310,109395,109396,109398,109399). There is insufficient reliable information available about the safety of sodium when used topically.

CHILDREN: LIKELY SAFE
when used orally and appropriately (26229,100310). Sodium is safe in amounts that do not exceed the CDRR intake level of 1.2 grams daily for children 1 to 3 years, 1.5 grams daily for children 4 to 8 years, 1.8 grams daily for children 9 to 13 years, and 2.3 grams daily for adolescents (100310).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Tell patients to avoid prolonged use of doses exceeding the CDRR intake level of 1.2 grams daily for children 1 to 3 years, 1.5 grams daily for children 4 to 8 years, 1.8 grams daily for children 9 to 13 years, and 2.3 grams daily for adolescents (100310). Higher intake can cause hypertension (26229).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Sodium is safe in amounts that do not exceed the CDRR intake level of 2.3 grams daily (100310).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in higher doses. Higher intake can cause hypertension (100310). Also, both the highest and the lowest pre-pregnancy sodium quintile intakes are associated with an increased risk of hypertensive disorders of pregnancy, including gestational hypertension and pre-eclampsia, and the delivery of small for gestational age (SGA) infants when compared to the middle intake quintile (106264).

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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).

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SCOPOLAMINE (Transderm Scop) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = B Theoretically, alpha-GPC might decrease the effects of scopolamine.  Details A small clinical study shows that alpha-GPC can partially counteract the attention and memory impairment effects caused by scopolamine given intramuscularly (12103). Whether alpha-GPC can decrease the beneficial anti-motion sickness effects of the scopolamine patch (Transderm Scop) is unclear.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

(Read more about CAFFEINE)

ADENOSINE (Adenocard) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, coffee might decrease the vasodilatory effects of adenosine and interfere with its use prior to stress testing.  Details Coffee contains caffeine. Caffeine is a competitive inhibitor of adenosine at the cellular level (38172). However, 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 such as caffeine, as well as 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, alcohol might increase the levels and adverse effects of caffeine.  Details Coffee contains caffeine. Concomitant use of alcohol and caffeine can increase caffeine serum concentrations and the risk of caffeine adverse effects. Alcohol reduces caffeine metabolism (6370,24693).

ALENDRONATE (Fosamax) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Coffee reduces alendronate bioavailability.  Details Separate coffee ingestion and alendronate administration by two hours. Coffee reduces alendronate bioavailability by 60% (11735).

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, coffee may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.  Details Coffee contains caffeine. Caffeine is reported to have antiplatelet activity (8028,8029). Theoretically, the caffeine in coffee might increase the risk of bleeding when used concomitantly with these agents. However, this interaction has not been reported in humans. There is some evidence that caffeinated coffee might increase the fibrinolytic activity in blood (8030).

ANTIDIABETES DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = B Theoretically, concomitant use of coffee and antidiabetes drugs might interfere with blood glucose control.  Details Coffee contains caffeine. Reports claim that caffeine might increase or decrease blood sugar levels (6024,8646).

BETA-ADRENERGIC AGONISTS Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = D Theoretically, concomitant use of large amounts of coffee might increase cardiac inotropic effects of beta-agonists.  Details Coffee contains caffeine. Caffeine can increase cardiac inotropic effects of beta-agonists (15).

CIMETIDINE (Tagamet) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Likely •  Level of Evidence = B Theoretically, cimetidine might increase the effects and adverse effects of caffeine in coffee.  Details Coffee contains caffeine. Cimetidine can reduce caffeine clearance by 31% to 42% (11736,24700).

CLOZAPINE (Clozaril) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, coffee might increase the levels and adverse effects of clozapine and acutely exacerbate psychotic symptoms.  Details Coffee contains caffeine. Caffeine can increase the effects and toxicity of clozapine. Caffeine doses of 400-1000 mg daily inhibit clozapine metabolism (5051). Clozapine is metabolized by cytochrome P450 1A2 (CYP1A2). Researchers speculate that caffeine might inhibit CYP1A2. However, there is no reliable evidence that caffeine affects CYP1A2. There is also speculation that genetic factors might make some patients be more sensitive to the interaction between clozapine and caffeine (13741).

CONTRACEPTIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, concomitant use might increase the effects and adverse effects of caffeine found in coffee.  Details Coffee contains caffeine. Oral contraceptive drugs can decrease caffeine clearance by 40% to 65% (2714,11737).

DIPYRIDAMOLE (Persantine) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, coffee might decrease the vasodilatory effects of dipyridamole and interfere with its use prior to stress testing.  Details Coffee contains caffeine. Caffeine is a methylxyanthine that may inhibit dipyridamole-induced vasodilation (11770,11772,24974,37985,53795). It is recommended that methylxanthines such as caffeine, as well as methylxanthine-containing products such as coffee, 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 might increase the risk of adverse effects from caffeine.  Details Coffee contains caffeine. In human research, disulfiram decreases the clearance and increases the half-life of caffeine (11840).

DIURETIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, concomitant use might increase the risk of hypokalemia.  Details Coffee contains caffeine. 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 of stimulant adverse effects.  Details Coffee contains caffeine. 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 (1275,6486,9740,10307). Tell patients to avoid taking caffeine with ephedrine and other stimulants.

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 Coffee contains caffeine. Estrogen inhibits caffeine metabolism (2714).

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 Coffee contains caffeine. Fluconazole decreases caffeine clearance by approximately 25% (11022,24978).

FLUVOXAMINE (Luvox) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, fluvoxamine might increase the levels and adverse effects of caffeine.  Details Coffee contains caffeine. Fluvoxamine reduces caffeine metabolism (6370,38287).

LAMOTRIGINE (Lamictal) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Coffee consumption can decrease the levels and clinical effects of lamotrigine.  Details A pharmacokinetic study in patients taking lamotrigine shows that consumption of coffee, both caffeinated and decaffeinated, can decrease the area under the concentration-time curve (AUC) and the peak plasma level (Cmax) of lamotrigine. Each additional cup of coffee reduced the AUC and Cmax by 4% and 3%, respectively. It is unclear whether this interaction is due to induction of lamotrigine metabolism or inhibition of lamotrigine absorption (107837).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Coffee can reduce the absorption of levothyroxine.  Details In some patients, coffee can reduce levothyroxine absorption, possibly through the formation of non-absorbable complexes. A pharmacokinetic study in these patients found that 25-30 mL of espresso coffee consumed with levothyroxine tablets delayed the time to peak plasma levels by 38-43 minutes, reduced the peak plasma level (Cmax) by 19% to 36%, and reduced the area under the curve (AUC) by 27% to 36%. Coffee consumed one hour after levothyroxine did not affect absorption (16401). It is not known whether this interaction occurs with other types of coffee. Tell patients to avoid drinking coffee at the same time that they take their levothyroxine, and for up to an hour afterwards.

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = D Theoretically, abrupt coffee withdrawal might increase the levels and adverse effects of lithium.  Details Coffee contains caffeine. Abrupt caffeine withdrawal can increase serum lithium levels (609). Two cases of lithium tremor that worsened with abrupt coffee withdrawal have been reported (609,610). There is also one case of a 2.8-fold increase in blood lithium levels after a patient taking lithium reduced his coffee consumption from 13-20 cups daily to 10 cups daily (97369).

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 Coffee contains caffeine. Mexiletine can decrease caffeine elimination by 50% (1260,11741,24981).

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 Coffee contains caffeine. 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 Coffee contains caffeine. 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, coffee might reduce the effects of pentobarbital.  Details Coffee contains caffeine. Theoretically, caffeine might negate the hypnotic effects of pentobarbital (13742).

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. Also, coffee may bind to phenothiazines and reduce their absorption.  Details Coffee contains caffeine. Phenothiazines can reduce the metabolism of caffeine by inhibiting cytochrome P450 1A2 (CYP1A2) (23573,23574). Additionally, the tannins in coffee may bind to phenothiazines in the gastrointestinal tract and reduce their absorption (626,627).

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 Coffee contains caffeine. Concomitant use of phenylpropanolamine and caffeine might cause an additive increase in blood pressure (11738). Phenylpropanolamine also seems to increase caffeine serum levels (13743).

PIOGLITAZONE (Actos) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, coffee might increase the levels and clinical effects of pioglitazone.  Details Coffee contains caffeine. 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 Coffee contains caffeine. Concomitant use of caffeine and quinolones can decrease caffeine clearance and increase effects and risk of adverse effects (606,607,608,23555,24695,24696,24697).

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 Coffee contains caffeine. Caffeine and riluzole are both metabolized by cytochrome P450 1A2 (CYP1A2), and concomitant use might reduce 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 Coffee contains caffeine. 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 Coffee contains caffeine. 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 = B Theoretically, coffee might increase the levels and adverse effects of theophylline.  Details Coffee contains caffeine, which can increase theophylline levels (11741,11862,24984).

TRICYCLIC ANTIDEPRESSANTS (TCAs) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, TCAs might bind with coffee constituents when taken at the same time.  Details In vitro research suggests that the tannins in coffee might cause precipitation of TCAs (626,627). However, this effect has not been reported in humans.

VERAPAMIL (Calan, others) 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 caffeine.  Details Coffee contains caffeine. Verapamil increases plasma caffeine concentrations by 25% (11741).

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ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = A Theoretically, a high intake of dietary sodium might reduce the effectiveness of antihypertensive drugs.  Details High intake of dietary sodium can increase systolic and diastolic blood pressure (26222). Also, high intake of sodium may necessitate increased use of antihypertensive medications to achieve blood pressure control in some patients, such as those with chronic kidney disease (26223).

CORTICOSTEROIDS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Concomitant use of mineralocorticoids and some glucocorticoids with sodium supplements might increase the risk of hypernatremia.  Details Mineralocorticoids and some glucocorticoids (corticosteroids) cause sodium retention. This effect is dose-related and depends on mineralocorticoid potency. It is most common with hydrocortisone, cortisone, and fludrocortisone, followed by prednisone and prednisolone (4425).

LITHIUM Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Altering dietary intake of sodium might alter the levels and clinical effects of lithium.  Details High sodium intake can reduce plasma concentrations of lithium by increasing lithium excretion (26225). Reducing sodium intake can significantly increase plasma concentrations of lithium and cause lithium toxicity in patients being treated with lithium carbonate (26224,26225). Stabilizing sodium intake is shown to reduce the percentage of patients with lithium level fluctuations above 0.8 mEq/L (112909). Patients taking lithium should avoid significant alterations in their dietary intake of sodium.

SODIUM-CONTAINING DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Concomitant use of sodium-containing drugs with additional sodium from dietary or supplemental sources may increase the risk of hypernatremia and long-term sodium-related complications.  Details The Chronic Disease Risk Reduction (CDRR) intake level of 2.3 grams of sodium daily indicates the intake at which it is believed that chronic disease risk increases for the apparently healthy population (100310). Some medications contain high quantities of sodium. When used in conjunction with sodium supplements or high-sodium diets, the CDRR may be exceeded. Additionally, concomitant use may increase the risk for hypernatremia; this risk is highest in the elderly and people with other risk factors for electrolyte disturbances.

TOLVAPTAN (Samsca) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = C Theoretically, concomitant use of tolvaptan with sodium might increase the risk of hypernatremia.  Details Tolvaptan is a vasopressin receptor 2 antagonist that is used to increase sodium levels in patients with hyponatremia (29406). Patients taking tolvaptan should use caution with the use of sodium salts such as sodium chloride.

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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)

General ...Orally, alpha-GPC seems to be well tolerated.
Serious Adverse Effects (Rare):
Orally: Stroke.

Dermatologic ...Orally, some patients can experience skin rash (12102). Intramuscularly, alpha-GPC can cause erythema at the injection site (12101).

Gastrointestinal ...Orally, alpha-GPC has been rarely associated with diarrhea, heartburn, nausea, and vomiting (12102).
Intramuscularly, alpha-GPC has been rarely associated with diarrhea, heartburn, nausea, and vomiting (12102).

Neurologic/CNS ...Orally, alpha-GPC has been rarely associated with dizziness, excitation, headache, and insomnia (12102). Alpha-GPC use for at least 2 months has also been associated with an elevated risk of stroke when compared with non-users or those who used alpha-GPC for less than 2 months (108883).
Intramuscularly, alpha-GPC has been rarely associated with confusion, excitation, fainting, headache, and insomnia (12102).

(Read more about ALPHA-GPC)

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 (98807,114658).

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, caffeinated or decaffeinated coffee is well tolerated in moderate amounts.
Most Common Adverse Effects:
Orally: Drinking coffee containing caffeine can cause agitation, anxiety, chest pain, diuresis, gastric distress, headache, insomnia, nervousness, premature heart rate, ringing in the ears, and vomiting. These effects are more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly). With chronic caffeine use, especially in large amounts, habituation, tolerance, and psychological dependence can occur.
Abrupt discontinuation of caffeine may result in physical withdrawal symptoms, including anxiety, decreased physical energy, depressed mood, difficulty concentrating, drowsiness, fatigue, headache, irritability, reduced alertness, and rhinorrhea.
Rectally: Coffee enemas have been linked to proctocolitis, severe electrolyte abnormalities, and septicemia leading to death.

Cardiovascular ...Orally, coffee containing caffeine can cause chest pain and premature heartbeat (8042,111045). These effects are more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042). Excessive doses of caffeine can cause massive catecholamine release and subsequent sinus tachycardia (11832,11838,13734,13735).
Although acute administration of caffeine can cause increased blood pressure, regular consumption does not seem to increase either blood pressure or pulse, even in hypertensive patients (1451,1452,2722,13739,105312). Drinking one or more cups of caffeinated coffee daily also doesn't seem to increase the risk of developing hypertension in habitual coffee drinkers (8033,13739,111037).
Epidemiological research has found that regular caffeine intake of up to 400 mg daily, or approximately 4 cups of caffeinated coffee, is not associated with an increased incidence of atrial fibrillation (38018,38076,91028,91034,97451,97453,105310), atherosclerosis (38033), cardiac ectopy (91127), stroke (37804), ventricular arrhythmia (95948,97453,105310), or cardiovascular disease (CVD) in general (37805,98806,104882). However, some observational research suggests that drinking at least 1 cup of coffee per week is associated with a 40% increased risk of atrial fibrillation, with the highest incidence of atrial fibrillation occurring in adults consuming at least 6 cups daily (111042). Also, one large, observational study found a J-shaped association between regular coffee consumption and the risk of developing acute coronary syndromes. Moderate consumption of less than 300 mL daily (about 1.3 cups) was associated with a lower risk of developing acute coronary syndromes, whereas regular consumption of 300 mL daily or more was associated with an increased risk (11318). In contrast, other observational research in people without a history of CVD has found that drinking more than 6 cups of coffee daily does not appear to be associated with an increased risk of developing coronary heart disease (14343). Also, in people with a history of CVD, population research has found that coffee consumption is associated with a reduction in CVD-related mortality (97373,97374,103997,103998,104594,104595,104882,105308,105311,105313,105314); however not all research agrees (112735). However, in current smokers with a history of acute coronary syndrome, consuming more than 3 cups of coffee daily is associated with more than a two-fold increased risk of overall mortality (105313). Also, population research in patients with severe hypertension, but not mild hypertension, suggests that drinking at least two cups of coffee daily is associated with a 2-fold increase in CVD mortality compared with non-coffee drinkers (111027).
Caffeine intake may pose a greater cardiovascular risk to subjects who are not regular caffeine users. Population research suggests that drinking caffeinated coffee might trigger a myocardial infarction (MI) in some people. People who drink one or fewer cups of coffee daily and are sedentary and have multiple risk factors for heart disease have a significantly increased risk of MI within an hour after drinking coffee. However, this risk appears diminished in people who routinely consume greater amounts of coffee on a daily basis (14497). In another population study, caffeinated coffee consumption was associated with an increased risk of ischemic stroke in subjects who didn't regularly drink coffee (38102).
Boiled coffee that is prepared without a filter appears to increase serum cholesterol and triglyceride levels (1353,4200,8036,8539). Drinking one liter of strong, unfiltered coffee daily for two weeks can raise serum cholesterol by 10% and serum triglycerides by 36% (1353). Tell patients to use coffee filters since these effects do not seem to occur with filtered coffee (4200,8036,8539).
Coffee can adversely affect homocysteine levels. Higher homocysteine levels have been associated with CVD. One liter of unfiltered strong coffee daily for two weeks can increase plasma homocysteine levels by 10% (1353). The same amount of filtered strong coffee appears to raise plasma homocysteine levels by 20%, although there have been no head-to-head comparisons of filtered versus unfiltered coffee (3344).

Dermatologic ...Some researchers suggest symptoms such as flushed face occur during caffeine withdrawal. However, withdrawal symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).

Endocrine ...Orally, excessive doses of caffeine can cause massive catecholamine release and subsequent metabolic acidosis, hyperglycemia, and ketosis (13734). Other symptoms include hypokalemia and respiratory alkalosis (11832,11838,13735).
Some evidence shows that caffeine, a constituent of coffee, is associated with fibrocystic breast disease, breast cancer, and endometriosis in females; however, this is controversial since findings are conflicting (8043). Restricting caffeine intake in patients with fibrocystic breast conditions doesn't seem to affect breast nodularity, swelling, or pain (8996). Population research suggests that exposure to caffeine is not associated with an increased risk of endometriosis (91035).
A population analysis of the Women's Health Initiative observational study has found no association between consumption of caffeine-containing beverages, such as coffee, 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).

Gastrointestinal ...Orally, coffee containing caffeine can cause gastric distress and vomiting. These effects are more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042,13734). There is also some evidence that consumption of three or more cups of caffeinated coffee might increase the risk of Helicobacter pylori infection (8034).
Caffeine withdrawal symptoms such as nausea and vomiting have been described. However, these symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).
Rectally, at least 5 cases of proctocolitis related to the use of coffee enemas have been reported (96868,103273).

Genitourinary ...The caffeine found in coffee is a known diuretic and may increase voiding, give a sense of urgency, and irritate the bladder (37874,37961,104580). In males 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 has been associated with increased severity of premenstrual syndrome (38177).

Hematologic ...There is evidence that coffee containing caffeine shortens whole blood fibrinolysis time (8030).
Rectally, coffee enemas have been linked to severe electrolyte abnormalities leading to death (3026,3347,3349,6652)

Hepatic ...Boiled coffee that is prepared without a filter appears to increase liver aminotransferase enzymes. Tell patients to use coffee filters since these effects do not seem to occur with filtered coffee (8539).

Immunologic ...Caffeine can cause anaphylaxis in sensitive individuals, although true IgE-mediated caffeine allergy seems to be relatively rare (11315).
Rectally, coffee enemas have been linked to septicemia leading to death (3026,3347,3349,6652).

Musculoskeletal ...Orally, there is preliminary evidence that use of greater than four cups of coffee daily can increase the risk of rheumatoid factor positive rheumatoid arthritis, but this association has not been confirmed (6482).
Epidemiological evidence regarding the relationship between caffeine use and the risk for osteoporosis is contradictory. Caffeine can increase urinary excretion of calcium (2669,10202,11317). Females identified 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 of less than 400 mg daily does not seem to significantly increase osteoporosis risk in most postmenopausal adults with normal calcium intake (2669,6025,10202,11317,98806).
Caffeine withdrawal symptoms, such as muscle tension and muscle pains, have been described. However, these symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).

Neurologic/CNS ...Orally, coffee containing caffeine can cause agitation, headache, insomnia, and nervousness, . These effects are more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042,11832,11838,13734,13735).
Combining ephedra with coffee can increase the risk of adverse effects, due to the caffeine contained in coffee. Jitteriness, seizures, and temporary loss of consciousness have been associated with the combined use of ephedra and caffeine (2729).
Some researchers suggest that symptoms such as headache; tiredness and fatigue; decreased energy, alertness, and attentiveness; drowsiness; decreased contentedness; difficulty concentrating; irritability; and lack of clear-headedness are typical of caffeine withdrawal (13738). Withdrawal symptoms such as delirium, nervousness, and restlessness have also been described. However, these symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).

Ocular/Otic ...Orally, coffee containing caffeine can cause ringing in the ears. This is more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042,13734). Coffee containing caffeine also increases intraocular pressure, starting about 30 minutes after consumption and persisting for at least 90 minutes. Decaffeinated coffee does not appear to affect intraocular pressure (8540).

Oncologic ...The association between consumption of coffee and pancreatic cancer is controversial. Coffee may increase the incidence of some types of pancreatic cancers, but it may decrease other types (8535,8536,8537). Some studies do not support this association, especially in patients that have never smoked (8038,8040,93878,103999). Patients who are at risk of pancreatic cancer (pancreatitis) should limit their consumption of coffee.
People who consume 2-4 or more cups of caffeinated coffee dail might have a significantly increased risk of developing lung cancer (13191,90177). But drinking decaffeinated coffee seems to be associated with a decreased risk of lung cancer (13191).
Coffee consumption has also been associated at various times with an increased risk of breast cancer, bladder cancer, colon cancer, and other types of cancers, but there's no good evidence that coffee consumption increases cancer risk (8039,8040,8041). Most human studies that have examined caffeine or coffee intake have found that they do not play a role in the development of various cancers, including breast or most gastric cancers (91054,91076,98806). However, drinking caffeinated coffee might increase the risk of gastric cardia cancer (91076).

Psychiatric ...Orally, coffee containing caffeine can cause anxiety. This is more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042,13734). With chronic use, especially in large amounts, habituation, tolerance, and psychological dependence can occur (3719). Other researchers suggest symptoms such as depressed mood are typical of caffeine withdrawal (13738). However, withdrawal symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).

Pulmonary/Respiratory ...Caffeine withdrawal symptoms such as rhinorrhea have been described. However, these symptoms may be due to nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon (2723,11839).

Renal ...Orally, coffee containing caffeine can cause diuresis. This is more likely with increasing intake of caffeine and in certain populations (e.g., children, elderly) (8042,13734).

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General ...Orally, sodium is well tolerated when used in moderation at intakes up to the Chronic Disease Risk Reduction (CDRR) intake level. Topically, a thorough evaluation of safety outcomes has not been conducted.
Serious Adverse Effects (Rare):
Orally: Worsened cardiovascular disease, hypertension, kidney disease.

Cardiovascular ...Orally, intake of sodium above the CDRR intake level can exacerbate hypertension and hypertension-related cardiovascular disease (CVD) (26229,98176,100310,106263). A meta-analysis of observational research has found a linear association between increased sodium intake and increased hypertension risk (109398). Observational research has also found an association between increased sodium salt intake and increased risk of CVD, mortality, and cardiovascular mortality (98177,98178,98181,98183,98184,109395,109396,109399). However, the existing research is unable to confirm a causal relationship between sodium intake and increased cardiovascular morbidity and mortality; high-quality, prospective research is needed to clarify this relationship (100312). As there is no known benefit with increased salt intake that would outweigh the potential increased risk of CVD, advise patients to limit salt intake to no more than the CDRR intake level (100310).
A reduction in sodium intake can lower systolic blood pressure by a small amount in most individuals, and diastolic blood pressure in patients with hypertension (100310,100311,106261). However, post hoc analysis of a small crossover clinical study in White patients suggests that 24-hour blood pressure variability is not affected by high-salt intake compared with low-salt intake (112910). Additionally, the available research is insufficient to confirm that a further reduction in sodium intake below the CDRR intake level will lower the risk for chronic disease (100310,100311). A meta-analysis of clinical research shows that reducing sodium intake increases levels of total cholesterol and triglycerides, but not low-density lipoprotein (LDL) cholesterol, by a small amount (106261).
It is unclear whether there are safety concerns when sodium is consumed in amounts lower than the adequate intake (AI) levels. Some observational research has found that the lowest levels of sodium intake might be associated with increased risk of death and cardiovascular events (98181,98183). However, this finding has been criticized because some of the studies used inaccurate measures of sodium intake, such as the Kawasaki formula (98177,98178,101259). Some observational research has found that sodium intake based on a single 24-hour urinary measurement is inversely correlated with all-cause mortality (106260). The National Academies Consensus Study Report states that there is insufficient evidence from observational studies to conclude that there are harmful effects from low sodium intake (100310).

Endocrine ...Orally, a meta-analysis of observational research has found that higher sodium intake is associated with an average increase in body mass index (BMI) of 1. 24 kg/m2 and an approximate 5 cm increase in waist circumference (98182). It has been hypothesized that the increase in BMI is related to an increased thirst, resulting in an increased intake of sugary beverages and/or consumption of foods that are high in salt and also high in fat and energy (98182). One large observational study has found that the highest sodium intake is not associated with overweight or obesity when compared to the lowest intake in adolescents aged 12-19 years when intake of energy and sugar-sweetened beverages are considered (106265). However, in children aged 6-11 years, usual sodium intake is positively associated with increased weight and central obesity independently of the intake of energy and/or sugar-sweetened beverages (106265).

Gastrointestinal ...In one case report, severe gastritis and a deep antral ulcer occurred in a patient who consumed 16 grams of sodium chloride in one sitting (25759). Chronic use of high to moderately high amounts of sodium chloride has been associated with an increased risk of gastric cancer (29405).

Musculoskeletal ...Observational research has found that low sodium levels can increase the risk for osteoporosis. One study has found that low plasma sodium levels are associated with an increased risk for osteoporosis. Low levels, which are typically caused by certain disease states or chronic medications, are associated with a more than 2-fold increased odds for osteoporosis and bone fractures (101260).
Conversely, in healthy males on forced bed rest, a high intake of sodium chloride (7.7 mEq/kg daily) seems to exacerbate disuse-induced bone and muscle loss (25760,25761).

Oncologic ...Population research has found that high or moderately high intake of sodium chloride is associated with an increased risk of gastric cancer when compared with low sodium chloride intake (29405). Other population research in patients with gastric cancer has found that a high intake of sodium is associated with an approximate 65% increased risk of gastric cancer mortality when compared with a low intake. When zinc intake is taken into consideration, the increased risk of mortality only occurred in those with low zinc intake, but the risk was increased to approximately 2-fold in this sub-population (109400).

Pulmonary/Respiratory ...In patients with hypertension, population research has found that sodium excretion is modestly and positively associated with having moderate or severe obstructive sleep apnea. This association was not found in normotensive patients (106262).

Renal ...Increased sodium intake has been associated with impaired kidney function in healthy adults. This effect seems to be independent of blood pressure. Observational research has found that a high salt intake over approximately 5 years is associated with a 29% increased risk of developing impaired kidney function when compared with a lower salt intake. In this study, high salt intake was about 2-fold higher than low salt intake (101261).

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General ...Orally, tyrosine seems to be well tolerated. No serious adverse effects have been documented; however, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Fatigue, headache, heartburn, and nausea.

Gastrointestinal ...Orally, tyrosine can cause nausea and heartburn when taken at a dose of 150 mg/kg (7211). Taking tyrosine 4 grams daily in combination with 5-hydroxytryptophan 800 mg and carbidopa 100 mg can cause diarrhea, nausea, and vomiting. These effects can be mitigated by lowering the dosage (918).

Musculoskeletal ...Orally, larger doses of tyrosine (150 mg/kg) can cause arthralgia, but this is uncommon (7211).

Neurologic/CNS ...Orally, larger doses of tyrosine (150 mg/kg) can cause headache and fatigue (7211). Taking a combination of tyrosine 4 grams, 5-hydroxytryptophan 800 mg, and carbidopa 100 mg can cause drowsiness and agitation. These effects can be mitigated by lowering the dosage (918).

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