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Caf9.5
Caffeine Research
Likely helps
1,037 peer-reviewed studies
What the evidence says
Likely helps
Caffeine appears to help in 29 of 35 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2008–2026 with a typical study size of 91 participants.
Based on 1,037 studies · 164 meta-analyses · 733 RCTs · 278,220 total participants
Confidence
High confidence
What the studies found
29helped5unclear1didn't help· 1002 more without graded effect data
By outcome
Cognitive functionEnhances short-term memory consolidation and recall · 30-60 minutes
However, aerobic responses to caffeine vary substantially, with time-trial performance ranging from ~-3% to +16%.
Data were pooled using standardized mean differences (SMDs) and 95% confidence intervals under random-effects models, and risk of bias was assessed using the Cochrane Risk of Bias tool.
Both low and moderate caffeine doses significantly reduced time-trial completion time relative to placebo.
The relationship between caffeine intake and IBD risk varies by region, age, caffeine source, smoking, and education level.
Wu X et al. · Journal of gastroenterology and hepatology (2026)
No clear effect
← WorseNo effectBetter →
The meta-analysis showed no significant association between caffeine intake and IBD (RR = 0.84, 95% CI = 0.68-1.04).
In Americans, caffeine increased UC risk by 68% (RR = 1.68, 95% CI = 1.17-2.42).
Age analysis showed caffeine increased IBD risk by 4.52 times in those ≤18 (RR = 4.52, 95% CI = 1.59-12.88) but decreased risk by 7% in those >18 (RR = 0.93, 95% CI = 0.73-1.18).
3Fat oxidation rate during exerciseMeta-AnalysisCited 36×n=2,020 · very large study2020
However, the fitness level of the participant may modulate the magnitude of the effect of caffeine on fat oxidation during exercise.
Collado-Mateo D et al. · Nutrients (2020)
Large benefit
← WorseNo effectBetter →
Likely real
A subsequent meta-analysis was performed using the random effects model to calculate the standardized mean difference (SMD).
The meta-analysis revealed that caffeine significantly (p = 0.008) increased the fat oxidation rate (SMD = 0.73; 95% CI = 0.19 to 1.27).
This increment was consistent with a significant (p = 0.04) reduction of the respiratory exchange ratio (SMD = -0.33; 95% CI = -0.65 to -0.01) and a significant (p = 0.049) increase in the oxygen uptake (SMD = 0.23; 95% CI = 0.01 to 0.44).