Caffeine
Performance
The most effective legal stimulant, and the easiest one to build tolerance to.
What the evidence says
Very large human trial base for endurance and alertness. Tolerance to the alertness effect develops within days.
What studies used
100–300 mg; 3–6 mg/kg in performance trials. Cut it 8–10 h before bed — the half-life is ~5 h.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- Wrecks sleep long after you stop feeling it
- Stacks silently across coffee, pre-workout and energy drinks
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Strong) is the read on quality.
Research (12)
- Caffeine: cognitive and physical performance enhancer or psychoactive drug?Curr Neuropharmacol · 2015
- Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?J Int Soc Sports Nutr · 2024
- Caffeine and exercise: metabolism, endurance and performanceSports Med · 2001
- Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine ConsumptionPharmacol Rev · 2018
- Coffee and mental disorders: How caffeine affects anxiety and depressionProg Brain Res · 2024
- Is caffeine a cognitive enhancer?J Alzheimers Dis · 2010
- Effects of caffeine on human behaviorFood Chem Toxicol · 2002
- Effects of caffeine on sleep quality and daytime functioningRisk Manag Healthc Policy · 2018
- Effects of Caffeine on Resistance Exercise: A Review of Recent ResearchSports Med · 2021
- Genetic susceptibility to caffeine intake and metabolism: a systematic reviewJ Transl Med · 2024
- Caffeine (1, 3, 7-trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory mattersJ Food Sci · 2010
- Effect of Caffeine Consumption on the Risk for Neurological and Psychiatric Disorders: Sex Differences in HumanNutrients · 2020
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