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Head-to-head evidence comparison — which supplement is right for you?
Caffeine vs Magnesium: Caffeine has the stronger overall evidence (9.5 vs 8.5/10); they're alternatives for sharpen focus — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Caffeine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
29 of 35 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
12 of 16 studies with measurable effects showed benefit.
Top outcomes
100-200mg
Morning, 30-60 minutes before exercise
Pill/capsule for precise dosing
200-350mg elemental magnesium daily
Evening for sleep/relaxation (glycinate), Morning for energy (malate), Anytime (citrate)
Depends on goal - see notes
Optimal timing separates stimulating and relaxing effects
Take caffeine in morning (before 2pm), magnesium in evening.
15-45 minutes
30-60 minutes
30-60 minutes
30-60 minutes
1-2 weeks
1-2 weeks
1 week
Immediate
Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis
Nutrients (2020) · Meta analysis · n=2020
A subsequent meta-analysis was performed using the random effects model to calculate the standardized mean difference (SMD).
The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials
Critical reviews in food science and nutrition (2019) · Meta analysis · n=606
Thirteen RCTs with 606 participants were included in the meta-analyses.
Effect of Caffeine and Nitrates Combination on Exercise Performance, Heart Rate and Oxygen Uptake: A Systematic Review and Meta-Analysis
Nutrients (2024) · Meta analysis · n=95
The meta-analysis revealed that caffeine and nitrates supplementation (CAF+nitrates) did not enhance performance in time trials (TTs) over the CAF alone (g = -0.06; 95% CI = -0.46 to 0.35; p = 0.78) or nitrates alone (g = 0.29; 95% CI = -0.12 to 0.70; p = 0.17).
Magnesium supplementation in pregnancy
The Cochrane database of systematic reviews (2014) · Meta analysis · n=9090
Women receiving magnesium were significantly less likely to require hospitalisation during pregnancy (RR 0.65, 95% CI 0.48 to 0.86; three trials, 1158 women).Of the 10 trials included in the review, only two were judged to be of high quality overall.
Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis
Hypertension (2025) · Meta analysis · n=2709
38 RCTs with 2709 participants analyzed
Magnesium and Potassium Supplementation for Systolic Blood Pressure Reduction in the General Normotensive Population: A Systematic Review and Subgroup Meta-Analysis for Optimal Dosage and Treatment Length
Nutrients (2024) · Meta analysis
Both supplements demonstrated greater reductions in SBP for the general population at lower dosages and longer treatment durations.
Based on multiple meta-analyses showing 3-6mg/kg optimal dosing. Performance benefits plateau around 200-300mg with increased jitteriness at higher doses.
Based on meta-analysis of 38 RCTs with 2709 participants showing -7.68 mmHg reduction in hypertensive individuals. Effects are greatest in those with hypomagnesemia. Limited evidence in normotensive populations.
AI-estimated from published studies. Interpret as directional guidance.
Caffeine has a higher evidence score (9.5/10 vs 8.5/10) and wins in 2 of 3 categories.
For sharpen focus, Caffeine has a higher relevance score (90 vs 70).
Optimal timing separates stimulating and relaxing effects Take caffeine in morning (before 2pm), magnesium in evening. Consult a healthcare provider for personalized advice.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.