{"@context":"https://schema.org","@type":"DietarySupplement","id":"https://nutripedia.co.uk/items/caffeine","url":"https://nutripedia.co.uk/items/caffeine","name":"Caffeine","category":"Performance","tagline":"The world's most popular stimulant — proven ergogenic aid.","verdict":"strong","evidenceRating":5,"verdictSummary":"Robust evidence for improved endurance, strength, and cognitive performance. Well-tolerated in moderate doses.","dosage":{"recommended":"3–6","unit":"mg/kg","timing":"30–60 minutes before exercise","notes":"Individual tolerance varies. Avoid within 6 hours of bedtime."},"keyBenefits":["Improves endurance and time-to-exhaustion","Enhances alertness and reaction time","May increase fat oxidation during exercise","Acute strength and power benefits"],"warnings":["Can cause anxiety, jitteriness, and insomnia at high doses","Tolerance develops with chronic use","Not recommended for children or during pregnancy","Avoid combining with other stimulants"],"evidenceSummary":null,"dosing":null,"safety":null,"whoMightBenefit":[],"whoShouldAvoid":[],"regulatoryNotes":null,"faqs":[{"question":"What does the research say about caffeine and endurance performance?","answer":"A 2020 umbrella review of 21 meta-analyses concluded caffeine is one of the most effective ergogenic supplements available, significantly improving endurance performance, muscle strength, anaerobic power, and speed. Earlier meta-analyses found mean improvements in time-to-exhaustion of approximately 12%, and time-trial performance improvements of roughly 2–4%. The International Society of Sports Nutrition, IOC, and Australian Institute of Sport all classify caffeine as an evidence-based ergogenic aid."},{"question":"What dosage ranges have been studied for caffeine?","answer":"EFSA's 2015 scientific opinion identified 3 mg/kg body weight as the dose reliably improving exercise performance without adverse effects, equivalent to approximately 200 mg for a 70 kg adult. The EFSA reference daily intake for adults is 400 mg/day from all sources combined. Performance trials have studied 1–9 mg/kg; doses above 6 mg/kg show diminishing returns and increased adverse event rates. NHS guidance limits caffeine to 200 mg/day during pregnancy."},{"question":"What side effects have been reported in caffeine trials?","answer":"Commonly reported adverse events at doses above 3–6 mg/kg include anxiety, jitteriness, GI discomfort, and tachycardia. Chronic high-dose use leads to tolerance development and withdrawal symptoms (headache, fatigue, irritability) on cessation. At doses of 400 mg taken 6 hours before bed, RCT data show sleep onset delay and approximately 1-hour reduction in total sleep time. EFSA set 1.4 mg/kg as the single-dose threshold above which adverse cardiovascular effects may occur in sensitive individuals."},{"question":"Is there evidence for caffeine use during pregnancy?","answer":"NHS guidance advises pregnant women to limit total caffeine intake to 200 mg/day from all sources (coffee, tea, energy drinks, chocolate). This recommendation is based on observational cohort data associating higher maternal caffeine intake with increased risk of foetal growth restriction and miscarriage. EFSA's 2020 scientific opinion on caffeine safety during pregnancy found consistent evidence of risk at intakes above 200 mg/day and recommended the NHS limit be maintained."},{"question":"Does tolerance to caffeine reduce its ergogenic effects?","answer":"This is debated in the literature. Some studies suggest habitual caffeine users show blunted performance response, while others find equivalent effects regardless of habitual intake. A 2019 meta-analysis found no significant interaction between habitual caffeine use and ergogenic effect size. ISSN guidance suggests low-caffeine consumers may experience larger performance effects, but caffeine withdrawal (3–7 days abstinence before competition) has not been shown to enhance performance response in well-controlled trials."},{"question":"Which form of caffeine has the strongest evidence base?","answer":"Anhydrous caffeine (tablets/capsules) is the form used in the majority of exercise performance RCTs and provides reliable, measurable doses. Coffee provides caffeine plus other bioactive compounds (chlorogenic acids) and has also been studied in performance trials with comparable effects. Caffeine citrate is used in clinical settings (neonatal apnoea) and is faster-absorbed than anhydrous. Sustained-release caffeine has been studied for prolonged exercise with limited evidence of superiority over standard anhydrous forms."},{"question":"What does EFSA say about caffeine safety?","answer":"EFSA published a comprehensive scientific opinion on caffeine safety in 2015, concluding that habitual caffeine intakes up to 400 mg/day are safe for healthy adults and do not raise safety concerns. Single doses up to 200 mg (3 mg/kg) do not raise safety concerns for adult performance contexts. For children and adolescents, EFSA recommended a limit of 3 mg/kg/day. The 200 mg/day limit during pregnancy is specifically noted. EFSA has authorised a health claim for caffeine and increased endurance performance at 3 mg/kg."}],"research":{"totalCount":14,"papers":[{"title":"Effects of Different Doses of Caffeine on Cognitive Performance in Healthy Physically Active Individuals","year":2024,"journal":"European Journal of Nutrition","doi":"10.1007/s00394-024-03486-9","pmid":"39231871","url":"https://doi.org/10.1007/s00394-024-03486-9","studyDesign":"rct","fields":[],"conclusion":"Reaction time improved only at 6 mg/kg caffeine vs placebo in physically active adults. Sustained attention, anticipation, and memory were unaffected at either dose. The 6 mg/kg dose also increased the incidence of side effects, suggesting a narrow benefit-to-risk window for high-dose cognitive use.","abstract":"","citationCount":0},{"title":"The Effect of Caffeine Supplementation on Muscular Strength and Endurance: A Meta-Analysis of Meta-Analyses","year":2024,"journal":"Heliyon","doi":"10.1016/j.heliyon.2024.e35025","pmid":"39170391","url":"https://doi.org/10.1016/j.heliyon.2024.e35025","studyDesign":"meta-analysis","fields":[],"conclusion":"Synthesis of 9 meta-analyses confirmed caffeine supplementation significantly increases muscle strength (SMD=0.18, p<0.001) and muscle endurance (SMD=0.30, p<0.001). Authors note a gap in research specifically examining female athletes and hormonal influences on outcomes.","abstract":"","citationCount":0},{"title":"Effect of Caffeine Ingestion on Time Trial Performance in Cyclists: A Systematic Review and Meta-Analysis","year":2024,"journal":"Journal of the International Society of Sports Nutrition","doi":"10.1080/15502783.2024.2363789","pmid":"38836626","url":"https://doi.org/10.1080/15502783.2024.2363789","studyDesign":"meta-analysis","fields":[],"conclusion":"Moderate caffeine doses (4–6 mg/kg) significantly improved cycling time-trial performance in terms of both completion time and power output. Low doses (1–3 mg/kg) produced non-significant effects, identifying 4–6 mg/kg as the optimal ergogenic range for cyclists.","abstract":"","citationCount":0},{"title":"Caffeine Intake and Anxiety: A Meta-Analysis","year":2024,"journal":"Frontiers in Psychology","doi":"10.3389/fpsyg.2024.1270246","pmid":"38362247","url":"https://doi.org/10.3389/fpsyg.2024.1270246","studyDesign":"meta-analysis","fields":[],"conclusion":"Across 14 studies (546 participants) caffeine elevated anxiety risk in a dose-dependent manner. Lower doses produced modest increases; intake exceeding 400 mg/day resulted in substantially higher anxiety risk. Individuals with anxiety sensitivity may be particularly susceptible.","abstract":"","citationCount":0},{"title":"Moderators of Caffeine's Effects on Jumping Performance in Females: A Systematic Review and Meta-Analysis","year":2024,"journal":"Journal of the American Nutrition Association","doi":"10.1080/27697061.2023.2212740","pmid":"37191618","url":"https://doi.org/10.1080/27697061.2023.2212740","studyDesign":"meta-analysis","fields":[],"conclusion":"Caffeine ingestion produced a significant ergogenic effect on vertical jumping performance in females (g=0.28) across 15 studies. Performance gains were notably larger during the follicular phase of the menstrual cycle, highlighting hormonal modulation of caffeine's ergogenic response.","abstract":"","citationCount":0},{"title":"International Society of Sports Nutrition Position Stand: Coffee and Sports Performance","year":2023,"journal":"Journal of the International Society of Sports Nutrition","doi":"10.1080/15502783.2023.2237952","pmid":"37498180","url":"https://doi.org/10.1080/15502783.2023.2237952","studyDesign":"position-stand","fields":[],"conclusion":"Coffee is a complex matrix with neuromuscular, antioxidant, metabolic and cognitive effects relevant to sport. Its ergogenic impact varies by serving size, bean type, and brew method. Caffeine from coffee confers similar performance benefits to caffeine anhydrous.","abstract":"","citationCount":0},{"title":"The Effect of Caffeine on Subsequent Sleep: A Systematic Review and Meta-Analysis","year":2023,"journal":"Sleep Medicine Reviews","doi":"10.1016/j.smrv.2023.101764","pmid":"36870101","url":"https://doi.org/10.1016/j.smrv.2023.101764","studyDesign":"meta-analysis","fields":[],"conclusion":"Caffeine reduced total sleep time by ~45 minutes and sleep efficiency by ~7%, and increased sleep onset latency by ~9 minutes. Coffee should be avoided ≥8.8 hours before bed; pre-workout supplements ≥13.2 hours before bed to minimise sleep disruption.","abstract":"","citationCount":0},{"title":"Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis","year":2022,"journal":"Nutrients","doi":"10.3390/nu15010148","pmid":"36615805","url":"https://doi.org/10.3390/nu15010148","studyDesign":"meta-analysis","fields":[],"conclusion":"Analysis of 21 RCTs (254 participants) found caffeine produced a medium ergogenic effect on time-to-exhaustion running and a smaller improvement in time-trial completion time at doses of 3–9 mg/kg. Benefits were consistent across recreational and trained runners.","abstract":"","citationCount":0},{"title":"Does Acute Caffeine Supplementation Improve Physical Performance in Female Team-Sport Athletes? Evidence from a Systematic Review and Meta-Analysis","year":2021,"journal":"Nutrients","doi":"10.3390/nu13103663","pmid":"34684665","url":"https://doi.org/10.3390/nu13103663","studyDesign":"meta-analysis","fields":[],"conclusion":"Caffeine improved specific team-sport skills, countermovement jump, and grip strength in female athletes but showed no significant effect on agility, sprint ability, or perceived exertion. Findings support selective use of caffeine supplementation in female team-sport contexts.","abstract":"","citationCount":0},{"title":"The Neurophysiology of Caffeine as a Central Nervous System Stimulant and the Resultant Effects on Cognitive Function","year":2021,"journal":"Cureus","doi":"10.7759/cureus.15032","pmid":"34150383","url":"https://doi.org/10.7759/cureus.15032","studyDesign":"systematic-review","fields":[],"conclusion":"Caffeine blocks adenosine A1 and A2A receptors, indirectly elevating dopamine, norepinephrine, and acetylcholine. This mechanism improves processing speed and memory in adults and older populations but evidence on attention is mixed and effects in children appear negative.","abstract":"","citationCount":0},{"title":"Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis","year":2021,"journal":"Nutrients","doi":"10.3390/nu13030868","pmid":"33800853","url":"https://doi.org/10.3390/nu13030868","studyDesign":"meta-analysis","fields":[],"conclusion":"Low-to-moderate caffeine doses before or during exercise significantly improved attention, accuracy, and simple reaction time in athletes. Benefits to memory and complex cognition were less consistent. Self-reported energy and mood also improved across included studies.","abstract":"","citationCount":0},{"title":"International Society of Sports Nutrition Position Stand: Caffeine and Exercise Performance","year":2021,"journal":"Journal of the International Society of Sports Nutrition","doi":"10.1186/s12970-020-00383-4","pmid":"33388079","url":"https://doi.org/10.1186/s12970-020-00383-4","studyDesign":"position-stand","fields":[],"conclusion":"Caffeine at 3–6 mg/kg body mass consistently improves aerobic endurance, muscular endurance, strength, sprint, and power output in trained and untrained individuals. Effects are modulated by genetics, habitual intake, and delivery method. Optimal timing is ~60 min pre-exercise.","abstract":"","citationCount":0},{"title":"Wake Up and Smell the Coffee: Caffeine Supplementation and Exercise Performance — an Umbrella Review of 21 Published Meta-Analyses","year":2020,"journal":"British Journal of Sports Medicine","doi":"10.1136/bjsports-2018-100278","pmid":"30926628","url":"https://doi.org/10.1136/bjsports-2018-100278","studyDesign":"systematic-review","fields":[],"conclusion":"Across 21 meta-analyses, caffeine consistently improved aerobic endurance, muscle strength, muscle endurance, jumping, and power output. Effect magnitudes are generally larger for aerobic than anaerobic exercise. Most evidence is from young males, limiting broader generalisability.","abstract":"","citationCount":0},{"title":"Scientific Opinion on the Safety of Caffeine","year":2015,"journal":"EFSA Journal","doi":"10.2903/j.efsa.2015.4102","pmid":"","url":"https://doi.org/10.2903/j.efsa.2015.4102","studyDesign":"regulatory","fields":[],"conclusion":"Single caffeine doses up to 200 mg (≈3 mg/kg for a 70 kg adult) do not raise safety concerns. Habitual intake up to 400 mg/day is safe for non-pregnant healthy adults. Pregnant women should limit intake to 200 mg/day from all sources.","abstract":"","citationCount":0}]},"machineReadable":{"markdownUrl":"https://nutripedia.co.uk/items/caffeine/markdown","jsonUrl":"https://nutripedia.co.uk/items/caffeine/json","llmsTxt":"https://nutripedia.co.uk/llms.txt"},"disclaimer":"Informational supplement research only. Not medical advice. Consult a qualified healthcare professional before taking supplements.","lastReviewed":"2026-04-20T00:00:00.000Z","updatedAt":"2026-04-20T00:00:00.000Z"}