Caffeine

    Written by:
    Thomas Solomon

    Fact-checked

    by:

    Nick Milazzo
    Last Updated: December 18, 2023

    Caffeine is a central nervous system stimulant that can improve sports performance and aspects of cognitive function. Caffeine or caffeine-containing beverages are often taken to help restore alertness and wakefulness or to reduce drowsiness. Despite its side effects, caffeine is safe for most people, and caffeine-containing beverages like tea and coffee are socially acceptable and widely used.

    164 references on this page
    13,873 participants in 47 trials and 16 meta-analyses

    Overview

    Dosage information

    For sports performance

    The optimal dose for sports performance benefits is 3–6 mg per kilogram of bodyweight (approximately 200–400 mg in a 70 kg person), taken around 60 minutes before exercise.[1] Using a dose at the low end of this range, approximately 3 mg/kg of caffeine before exercise (approximately 200 mg in a 70 kg person), achieves the benefits along with the lowest risk of side effects.[2]

    Safety in adults

    Caffeine is generally safe for most people if used within the recommended amounts.[3][4] The US Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) report that a daily total caffeine intake of up to 400 milligrams (mg) does not raise safety concerns for non-pregnant adults.[5][6] The EFSA further reports that a daily total caffeine intake of up to 200 mg in pregnant and lactating women does not increase safety concerns for unborn babies or breastfed infants, and that a single caffeine dose of up to 200 mg (approximately 3 mg per kg bodyweight for a 70-kg adult) does not raise safety concerns.[5] In other words, caffeine intake is unlikely to cause detrimental health effects if daily intake is below 400 mg/day in non-pregnant adults, or below 200 mg/day in pregnant/lactating women, and if a single dose is less than 200 mg.

    Safety in children and teens

    In children and adolescents, more research is needed to clarify safety, health risks, and tolerable upper intake limits.[5] Evidence from a systematic review suggests that children and adolescents should consume no more than 2.5 mg per kg of bodyweight per day (equivalent to 100 mg for a 40 kg person).[3] But some organizations discourage all consumption of caffeine and other stimulants by children and adolescents.[6]

    Caffeine in food and drink

    Caffeine concentrations in various foods — coffee, tea, soft drinks (cola), chocolate, energy drinks, etc — are highly variable.[5] For example, a cup of coffee may contain approximately 50–200 mg of caffeine, but the amount per cup is highly variable depending on the type of bean, how it is roasted, and how it is prepared.[7][8] Some energy drinks contain very high amounts of caffeine, and the FDA recommends avoiding dietary supplements that contain pure or highly concentrated caffeine because a single teaspoon of pure powdered caffeine contains about 5 grams (5000 milligrams), far higher than the upper recommended limit of daily intake and approaching the toxic dose.[9]

    For a detailed overview of caffeine dosing, read our article “How Much Caffeine Is Too Much?”.

    Caffeine in caffeine citrate

    Note that caffeine citrate is about 50% caffeine by weight, i.e., a 50 mg dose of caffeine citrate contains approximately 25 mg of caffeine.[10][11]

    Examine Database: Caffeine

    General Athletic Performance
    Cognitive Improvement
    Metabolic Health
    Aerobic Exercise Performance
    Cycling Performance
    Muscle Size & Strength
    Focus & Attention
    Anaerobic Exercise Performance
    General Cardiovascular Health
    Pain Relief
    Running Performance
    Asthma
    High Blood Pressure
    Low Testosterone
    Type 2 Diabetes
    Fatigue
    High-Altitude Performance
    Muscle Recovery
    Rowing Performance
    Rugby Performance
    Sleep Health
    Warm- Or Hot-Weather Exercise Performance
    Weight Loss & Maintenance
    Postdural Puncture Headache
    Healthy Muscle Aging

    Frequently asked questions

    Update History

    Correction

    correction

    Research written by

    Thomas Solomon

    One new meta analysis added

    minor

    Reviewed by

    Nick Milazzo

    Examine Database References

    1. Anaerobic Capacity - Lamina S, Musa DIErgogenic effect of varied doses of coffee-caffeine on maximal aerobic power of young African subjectsAfr Health Sci.(2009 Dec)
    2. Subjective Well-Being - Duncan MJ, Oxford SWThe effect of caffeine ingestion on mood state and bench press performance to failureJ Strength Cond Res.(2011 Jan)
    3. Blood Lactate (Exercise) - Karapetian GK, Engels HJ, Gretebeck KA, Gretebeck RJEffect of Caffeine on LT, VT and HRVTInt J Sports Med.(2012 Apr 12)
    4. Blood Lactate (Exercise) - Norager CB, Jensen MB, Weimann A, Madsen MRMetabolic effects of caffeine ingestion and physical work in 75-year old citizens. A randomized, double-blind, placebo-controlled, cross-over studyClin Endocrinol (Oxf).(2006 Aug)
    5. Heart Rate - Del Coso J, Salinero JJ, Gonzalez-Millan C, Abian-Vicen J, Perez-Gonzalez BDose response effects of a caffeine-containing energy drink on muscle performance: a repeated measures designJ Int Soc Sports Nutr.(2012 May 8)
    6. Training Volume - Cook C, Beaven CM, Kilduff LP, Drawer SAcute caffeine ingestion increases voluntarily chosen resistance training load following limited sleepInt J Sport Nutr Exerc Metab.(2012 Feb 15)
    7. Adrenaline - Anderson DE, Hickey MSEffects of caffeine on the metabolic and catecholamine responses to exercise in 5 and 28 degrees CMed Sci Sports Exerc.(1994 Apr)
    8. Power Output - Mora-Rodríguez R, Pallarés JG, López-Samanes A, Ortega JF, Fernández-Elías VECaffeine ingestion reverses the circadian rhythm effects on neuromuscular performance in highly resistance-trained menPLoS One.(2012)
    9. Power Output - Todd A Astorino, Michael N Terzi, Daniel W Roberson, Timothy R BurnettEffect of two doses of caffeine on muscular function during isokinetic exerciseMed Sci Sports Exerc.(2010 Dec)
    10. Power Output - Beaven CM, Hopkins WG, Hansen KT, Wood MR, Cronin JB, Lowe TEDose effect of caffeine on testosterone and cortisol responses to resistance exerciseInt J Sport Nutr Exerc Metab.(2008 Apr)
    11. Rating of Perceived Exertion - Bellar D, Kamimori GH, Glickman ELThe effects of low-dose caffeine on perceived pain during a grip to exhaustion taskJ Strength Cond Res.(2011 May)
    12. Thermogenesis - Kim TW, Shin YO, Lee JB, Min YK, Yang HMCaffeine increases sweating sensitivity via changes in sudomotor activity during physical loadingJ Med Food.(2011 Nov)
    13. Jump Height - .(2024-09-18)
    14. Blood Pressure - Wedick NM, Brennan AM, Sun Q, Hu FB, Mantzoros CS, van Dam RMEffects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trialNutr J.(2011 Sep 13)
    15. Blood Lactate (Exercise) - Glaister M, Patterson SD, Foley P, Pedlar CR, Pattison JR, McInnes GCaffeine and sprinting performance: dose responses and efficacyJ Strength Cond Res.(2012 Apr)
    16. Anaerobic Capacity - Schneiker KT, Bishop D, Dawson B, Hackett LPEffects of caffeine on prolonged intermittent-sprint ability in team-sport athletesMed Sci Sports Exerc.(2006 Mar)
    17. Anaerobic Capacity - Paton CD, Lowe T, Irvine ACaffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclistsEur J Appl Physiol.(2010 Dec)
    18. Heart Rate - Desbrow B, Biddulph C, Devlin B, Grant GD, Anoopkumar-Dukie S, Leveritt MDThe effects of different doses of caffeine on endurance cycling time trial performanceJ Sports Sci.(2012)
    19. Aerobic Exercise Metrics - Ganio MS, Johnson EC, Klau JF, Anderson JM, Casa DJ, Maresh CM, Volek JS, Armstrong LEEffect of ambient temperature on caffeine ergogenicity during endurance exerciseEur J Appl Physiol.(2011 Jun)
    20. Aerobic Exercise Metrics - Womack CJ, Saunders MJ, Bechtel MK, Bolton DJ, Martin M, Luden ND, Dunham W, Hancock MThe influence of a CYP1A2 polymorphism on the ergogenic effects of caffeineJ Int Soc Sports Nutr.(2012 Mar 15)
    21. Rating of Perceived Exertion - Backhouse SH, Biddle SJ, Bishop NC, Williams CCaffeine ingestion, affect and perceived exertion during prolonged cyclingAppetite.(2011 Aug)
    22. Rating of Perceived Exertion - Astorino TA, Terzi MN, Roberson DW, Burnett TREffect of caffeine intake on pain perception during high-intensity exerciseInt J Sport Nutr Exerc Metab.(2011 Feb)
    23. Pain - Christopher J Derry, Sheena Derry, R Andrew MooreCaffeine as an analgesic adjuvant for acute pain in adultsCochrane Database Syst Rev.(2014 Dec 11)
    24. Memory - Ker K, Edwards PJ, Felix LM, Blackhall K, Roberts ICaffeine for the prevention of injuries and errors in shift workers.Cochrane Database Syst Rev.(2010-May-12)
    25. Memory - Smillie LD, Gökçen ECaffeine enhances working memory for extravertsBiol Psychol.(2010 Dec)
    26. Memory - Mednick SC, Cai DJ, Kanady J, Drummond SPComparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memoryBehav Brain Res.(2008 Nov 3)
    27. Memory - Childs E, de Wit HSubjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine usersPsychopharmacology (Berl).(2006 May)
    28. Memory - Adan A, Serra-Grabulosa JMEffects of caffeine and glucose, alone and combined, on cognitive performanceHum Psychopharmacol.(2010 Jun)
    29. Reaction Time - Irwin C, Khalesi S, Desbrow B, McCartney DEffects of acute caffeine consumption following sleep loss on cognitive, physical, occupational and driving performance: A systematic review and meta-analysis.Neurosci Biobehav Rev.(2020-Jan)
    30. Reaction Time - Duvnjak-Zaknich DM, Dawson BT, Wallman KE, Henry GEffect of caffeine on reactive agility time when fresh and fatiguedMed Sci Sports Exerc.(2011 Aug)
    31. Reaction Time - Oliver LS, Sullivan JP, Russell S, Peake JM, Nicholson M, McNulty C, Kelly VGEffects of Nutritional Interventions on Accuracy and Reaction Time with Relevance to Mental Fatigue in Sporting, Military, and Aerospace Populations: A Systematic Review and Meta-Analysis.Int J Environ Res Public Health.(2021-Dec-28)
    32. Visual acuity (VA) - Gillingham R, Keefe AA, Keillor J, Tikuisis PEffect of caffeine on target detection and rifle marksmanshipErgonomics.(2003 Dec 15)
    33. Anxiety Symptoms - Rogers PJ, Hohoff C, Heatherley SV, Mullings EL, Maxfield PJ, Evershed RP, Deckert J, Nutt DJAssociation of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumptionNeuropsychopharmacology.(2010 Aug)
    34. Blood Lactate (Exercise) - Astrup A, Toubro S, Cannon S, Hein P, Breum L, Madsen JCaffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteersAm J Clin Nutr.(1990 May)
    35. Adrenaline - Keijzers GB, De Galan BE, Tack CJ, Smits PCaffeine can decrease insulin sensitivity in humansDiabetes Care.(2002 Feb)
    36. Insulin - Pizziol A, Tikhonoff V, Paleari CD, Russo E, Mazza A, Ginocchio G, Onesto C, Pavan L, Casiglia E, Pessina ACEffects of caffeine on glucose tolerance: a placebo-controlled studyEur J Clin Nutr.(1998 Nov)
    37. Glycemic Control - Greer F, Hudson R, Ross R, Graham TCaffeine ingestion decreases glucose disposal during a hyperinsulinemic-euglycemic clamp in sedentary humansDiabetes.(2001 Oct)
    38. Cortisol - Gavrieli A, Yannakoulia M, Fragopoulou E, Margaritopoulos D, Chamberland JP, Kaisari P, Kavouras SA, Mantzoros CSCaffeinated coffee does not acutely affect energy intake, appetite, or inflammation but prevents serum cortisol concentrations from falling in healthy menJ Nutr.(2011 Apr 1)
    39. Anaerobic Capacity - Hadjicharalambous M, Georgiades E, Kilduff LP, Turner AP, Tsofliou F, Pitsiladis YPInfluence of caffeine on perception of effort, metabolism and exercise performance following a high-fat mealJ Sports Sci.(2006 Aug)
    40. Heart Rate - Bloomer RJ, Harvey IC, Farney TM, Bell ZW, Canale REEffects of 1,3-dimethylamylamine and caffeine alone or in combination on heart rate and blood pressure in healthy men and womenPhys Sportsmed.(2011 Sep)
    41. Blood Flow - Shechter M, Shalmon G, Scheinowitz M, Koren-Morag N, Feinberg MS, Harats D, Sela BA, Sharabi Y, Chouraqui PImpact of acute caffeine ingestion on endothelial function in subjects with and without coronary artery diseaseAm J Cardiol.(2011 May 1)
    42. Wakefulness - Barry RJ, Clarke AR, Johnstone SJCaffeine and opening the eyes have additive effects on resting arousal measuresClin Neurophysiol.(2011 Oct)
    43. Reaction Time - Hunt MG, Momjian AJ, Wong KKEffects of diurnal variation and caffeine consumption on Test of Variables of Attention (TOVA) performance in healthy young adultsPsychol Assess.(2011 Mar)
    44. Heart Rate - Glaister M, Howatson G, Abraham CS, Lockey RA, Goodwin JE, Foley P, McInnes GCaffeine supplementation and multiple sprint running performanceMed Sci Sports Exerc.(2008 Oct)
    45. Reaction Time - Pontifex KJ, Wallman KE, Dawson BT, Goodman CEffects of caffeine on repeated sprint ability, reactive agility time, sleep and next day performanceJ Sports Med Phys Fitness.(2010 Dec)
    46. Blood Pressure - Renda G, Zimarino M, Antonucci I, Tatasciore A, Ruggieri B, Bucciarelli T, Prontera T, Stuppia L, De Caterina RGenetic determinants of blood pressure responses to caffeine drinkingAm J Clin Nutr.(2012 Jan)
    47. Heart Rate - Glaister M, Gissane CCaffeine and Physiological Responses to Submaximal Exercise: A Meta-AnalysisInt J Sports Physiol Perform.(2017 Sep 5)
    48. Aerobic Exercise Metrics - Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic ZWake up and smell the coffee: caffeine supplementation and exercise performance-an umbrella review of 21 published meta-analysesBr J Sports Med.(2019 Mar 29)
    49. Jump Height - Salinero JJ, Lara B, Del Coso JEffects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis.Res Sports Med.(2019)
    50. Anaerobic Capacity - Carr AJ, Gore CJ, Dawson BInduced alkalosis and caffeine supplementation: effects on 2,000-m rowing performanceInt J Sport Nutr Exerc Metab.(2011 Oct)
    51. Asthma Symptoms - Welsh EJ, Bara A, Barley E, Cates CJCaffeine for asthma.Cochrane Database Syst Rev.(2010-Jan-20)
    52. Sleep Duration - Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, Townshend A, Halson SLThe effect of caffeine on subsequent sleep: A systematic review and meta-analysis.Sleep Med Rev.(2023-Jun)
    53. Headaches - Hadavi SMR, Panah A, Shamohammadi S, Kanaani Nejad F, Sahmeddini MA, Asmarian NThe Prophylactic Effect of Acetaminophen and Caffeine on Post Dural Puncture Headache after Spinal Anesthesia for Cesarean Section: A Randomized Double-Blind Clinical Trial.Iran J Med Sci.(2024 Sep)
    54. Cognition - Talik TN, Penna EM, Hack BP, Harp A, Millard-Stafford MEffects of Acute Guarana (Paullinia cupana) Ingestion on Mental Performance and Vagal Modulation Compared to a Low Dose of Caffeine.Nutrients.(2024 Jun 15)
    55. Muscular Endurance - Chiu CH, Chen CC, Ali A, Wu SL, Wu CLThe Effect of Pre-Exercise Caffeine and Glucose Ingestion on Endurance Capacity in Hypoxia: A Double-Blind Crossover Trial.Nutrients.(2024 Oct 25)