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Head-to-head evidence comparison — which supplement is right for you?
Caffeine wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
22 of 25 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
9 of 13 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
Nutrients (2024) · 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.