Caffeine
Research reviewed: Up until 03/2026
Caffeine (1,3,7-Trimethylxanthine) is a dietary supplement with 9 published peer-reviewed studies involving 3,840 participants, researched for Athletic Performance, Cognitive Function, Fat Oxidation and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Athletic Performance
StrongCognitive Function
ModerateFat Oxidation
ModerateAlertness & Mood
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Athletic Performance
To evaluate the ergogenic effects of caffeine on endurance performance.
Study Type
Randomised, double-blind, crossover
Purpose
To evaluate the ergogenic effects of caffeine on endurance performance.
Dose
3-6 mg/kg BW caffeine
Participants
23 trained cyclists
Duration
Acute crossover
Results
Caffeine supplementation significantly improved time trial performance by 3.7% and reduced perceived exertion. Blood lactate and VO2max were not significantly different, suggesting central mechanisms are important.
How They Measured It
Time trial performance, VO2max, RPE, blood lactate
To quantify the ergogenic effect of caffeine across different exercise modalities.
Study Type
Meta-analysis
Purpose
To quantify the ergogenic effect of caffeine across different exercise modalities.
Dose
3-6 mg/kg BW
Participants
Pooled from 49 studies (>1,000 participants)
Duration
Acute supplementation
Results
Caffeine produced significant improvements in endurance (ES = 0.63), strength (ES = 0.20), and power (ES = 0.17). Caffeine is one of the most evidence-based ergogenic supplements available.
How They Measured It
Pooled performance outcomes (endurance, strength, power) across RCTs
To assess caffeine on resistance training volume and power in trained males.
Study Type
Randomised, double-blind, crossover
Purpose
To assess caffeine on resistance training volume and power in trained males.
Dose
5 mg/kg BW caffeine
Participants
22 strength-trained men
Duration
Acute crossover
Results
Caffeine significantly increased 1RM bench press, total training volume, and maximal bar velocity. Effect was maintained across multiple sets, confirming caffeine as an effective strength training ergogenic aid.
How They Measured It
1RM bench press, total training volume, bar velocity
Cognitive Function
To evaluate caffeine's effects on cognitive performance and alertness.
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate caffeine's effects on cognitive performance and alertness.
Dose
200 mg caffeine
Participants
64 healthy adults
Duration
Acute
Results
Caffeine significantly improved sustained attention, working memory, and vigilance. Reaction time was reduced and mood was elevated compared to placebo. Effects lasted 4-6 hours post-ingestion.
How They Measured It
Psychomotor vigilance test, sustained attention, working memory, mood questionnaire
To assess the cognitive effects of low-dose caffeine during sleep deprivation.
Study Type
Randomised, double-blind, crossover
Purpose
To assess the cognitive effects of low-dose caffeine during sleep deprivation.
Dose
200 mg caffeine vs placebo
Participants
37 sleep-deprived healthy adults
Duration
Acute (repeated doses during 3 nights sleep restriction)
Results
Caffeine significantly counteracted cognitive performance decrement and alertness loss during sleep restriction. Both subjective and objective measures improved vs placebo.
How They Measured It
Psychomotor vigilance, cognitive throughput, subjective alertness
Fat Oxidation
To evaluate caffeine supplementation on fat oxidation rate during steady-state exercise.
Study Type
Randomised, double-blind, crossover
Purpose
To evaluate caffeine supplementation on fat oxidation rate during steady-state exercise.
Dose
5 mg/kg BW caffeine
Participants
24 healthy adults
Duration
Acute
Results
Caffeine significantly increased fat oxidation rate (+31%) and elevated serum free fatty acids during moderate-intensity exercise. RER was significantly lower in the caffeine condition.
How They Measured It
Indirect calorimetry (RER), fatty acid oxidation rate, serum free fatty acids
To evaluate caffeine's role in weight management and fat oxidation.
Study Type
Systematic review
Purpose
To evaluate caffeine's role in weight management and fat oxidation.
Dose
100-400 mg/day
Participants
Multiple study populations
Duration
Various
Results
Caffeine increases resting metabolic rate by 4-11% and fat oxidation rate by up to 29%. Chronic caffeine intake may blunt these effects over time. Short-term thermogenic and fat-mobilising properties are well established.
How They Measured It
Review of RCTs on metabolic rate, fat oxidation, and body composition
Alertness & Mood
To assess the dose-response relationship of caffeine on mood and anxiety.
Study Type
Randomised, double-blind, crossover
Purpose
To assess the dose-response relationship of caffeine on mood and anxiety.
Dose
0, 75, 150, and 300 mg caffeine
Participants
30 healthy adults
Duration
Acute crossover
Results
Caffeine dose-dependently improved positive affect and alertness. At 75-150 mg, anxiety was not elevated. At 300 mg, anxiety increased in caffeine-sensitive individuals. Moderate caffeine doses optimise mood without increasing anxiety.
How They Measured It
PANAS mood scale, State-Trait Anxiety Inventory, alertness VAS
To examine long-term caffeine/coffee consumption and depression risk.
Study Type
Prospective cohort
Purpose
To examine long-term caffeine/coffee consumption and depression risk.
Dose
Habitual caffeine consumption
Participants
50,739 US women
Duration
10-year follow-up
Results
Higher habitual coffee consumption was associated with significantly lower risk of depression. Women consuming ≥4 cups/day had 20% lower risk of depression. Caffeine modulation of adenosine and monoamine pathways is the proposed mechanism.
How They Measured It
Depression diagnosis, dietary caffeine intake, psychiatric questionnaires
Frequently Asked Questions
Common questions about Caffeine research
There are currently 12 peer-reviewed studies on Caffeine (1,3,7-Trimethylxanthine), involving 3,840 total participants. Research covers Athletic performance, Cognitive function, Fat oxidation and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (9 human studies), and reported outcomes.
Caffeine has been researched for: Athletic performance, Cognitive function, Fat oxidation, Alertness & mood. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 9 out of 12 studies are human trials. Human trials carry more weight in our evidence scoring system.
Similar Supplements
Other supplements researched for similar health goals
