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Caffeine (1,3,7-Trimethylxanthine)
Blocks adenosine receptors to boost alertness, reaction time, and endurance — an umbrella review of 21 meta-analyses found it ergogenic for endurance, strength and power.
What the evidence says
Caffeine helped in about half (3/5) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2008–2026 with a typical study size of 75 participants.
Based on 980 studies · 154 meta-analyses · 686 RCTs · 146,688 total participants
Confidence
High confidenceWhat the studies found
By outcome
The 19 meta-analyses cited here, including an umbrella review of 21 published meta-analyses, consistently show caffeine improves alertness, cognition, and endurance/strength performance with well-characterized dose-response.
214 trials ongoing or recruiting · 793 completed on ClinicalTrials.gov
119 of the completed trials have posted results
Registered trials show research momentum for Caffeine, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Oct 2026
Under EU law (Reg. 1924/2006), EFSA reviews whether a specific health claim for Caffeine meets the evidence standard. These are independent regulatory decisions on claims — not studies, and never counted toward the evidence score above.
Not authorised by EFSA
“Caffeine (from tea/coffee/chocolate or added in pure form) Improves physical performance”
“Caffeine can increase resting metabolic rate. Caffeine supports thermogenesis and energy oxidation”
“Caffeine -Enhances physical performance. -Provides a performance edge -Can delay the onset of fatigue -Can increase exercise intensity/work rate”
“Not authorised” means the specific claim wording did not meet the EU’s evidence standard — often a matter of dossier or phrasing, not proof of no effect. EFSA judges marketing claims and is kept separate from our study-based evidence score.
Source: EU Register of nutrition and health claims (European Commission / EFSA) · register snapshot Feb 2013
Showing the 983 most recent of 1891 studies.
Caffeine is a natural stimulant found in coffee, tea, and cacao. It has strong evidence for improving alertness, reaction time, and endurance exercise performance. Effects are dose-dependent, and tolerance develops with regular use.
Prevents the tiredness signal from reaching your brain
Increases adrenaline and dopamine activity
Enhances fat burning during exercise
How Caffeine works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Limit to 200mg/day maximum
Not recommended; limit to minimal amounts
Use with caution or avoid; may worsen symptoms
Additive stimulant effects; may increase heart rate and blood pressure
May increase caffeine effects and cardiovascular stress
Ciprofloxacin inhibits CYP1A2, slowing caffeine metabolism and intensifying/prolonging its effects
Potent CYP1A2 inhibitor that markedly raises caffeine levels and prolongs its half-life, increasing jitteriness, insomnia, and cardiovascular effects
Increased theophylline toxicity risk
Dangerous cardiac stimulation, arrhythmias
Tip: Lower dose or take with L-theanine
Tip: Avoid afternoon/evening consumption
Tip: Lower dose
Tip: Taper gradually rather than stopping abruptly
Caffeine has an evidence score of 9.5/10 — very strong evidence based on 1878 indexed studies, including 19 meta-analyses. Blocks adenosine receptors to boost alertness, reaction time, and endurance — an umbrella review of 21 meta-analyses found it ergogenic for endurance, strength and power. Representative study: PMID 41320553.
The commonly studied dose of Caffeine is 100-200mg. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Caffeine is in the morning. Taking it with food is preferred. Caffeine is a methylxanthine adenosine receptor antagonist with a half-life of 3-7 hours (CYP1A2-dependent).
Caffeine has a safety rating of "moderate". That is a category, not a measure of individual risk, and there are precautions worth knowing. The most commonly reported side effects are jitteriness/anxiety, insomnia, increased heart rate. Use caution if any of these apply to you: Severe anxiety disorders; Uncontrolled high blood pressure; Heart arrhythmias.
Creatine
Likely helpsIncreases phosphocreatine stores for faster ATP regeneration, boosting strength, power output, and cognitive function under stress.
CoQ10
Likely helpsA lipid-soluble antioxidant central to mitochondrial energy production, with the strongest trial support for fertility/IVF outcomes and heart failure.
Phosphatidylserine
Too few graded studiesKey brain membrane phospholipid that facilitates neurotransmitter release, memory formation, and post-exercise cortisol reduction.
Urolithin A
Too few graded studiesPostbiotic that triggers mitophagy — the cleanup of damaged mitochondria — to support muscle health and cellular energy.
What Actually Works vs What’s Hype
The honest tier list — proven staples vs situational vs mostly marketing. The hub the other guides feed into.
Supplements for Energy & Fatigue
Tired? Why most "energy" pills only work if they fix a deficit — and how to find yours first.
Focus & Nootropics
Caffeine+L-theanine works; bacopa needs weeks; most "brain pills" are hype. The honest tier list.
Pre-Workout: What’s Worth It
Caffeine, citrulline, beta-alanine, creatine — the ingredients that work, at clinical doses (vs fairy dusting).
Supplement Timing & Combining
When to take what, with or without food, and which supplements compete vs pair well.
Explore: Best supplements for Athletic PerformanceBest supplements for Focus, Memory & MoodBest supplements for Vitality & LongevityBest supplements for Sleep
Reviewed by Dr. Baher Al Hakim · Last reviewed May 2026 · evidence from 1,891 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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