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Head-to-head evidence comparison — which supplement is right for you?
Caffeine wins 3 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
Mostly mechanism / observational
Top outcomes
100-200mg
Morning, 30-60 minutes before exercise
Pill/capsule for precise dosing
10-20mg p-synephrine 1-2x daily (≤50mg/day); avoid or minimize combining with caffeine/other stimulants
morning
Standardized p-synephrine (stated dose)
Increased cardiovascular stress, elevated heart rate and blood pressure
AVOID combination. Monitor cardiovascular status if used together.
15-45 minutes
30-60 minutes
30-60 minutes
30-60 minutes
Acute
Acute
Acute
Throughout use
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).
The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p-Synephrine: A Systematic Review and Meta-Analysis.
Nutrients (2022) · Meta analysis
Both systolic and diastolic blood pressure increased significantly after prolonged use (SBP 6.37 mmHg, P = 0.02; DBP 4.33 mmHg, P = 0.03)
Safety and efficacy of citrus aurantium for weight loss.
The American journal of cardiology (2004) · Systematic review
Only 1 eligible RCT identified (20 patients, 6 weeks)
An evidence-based systematic review of bitter orange (Citrus aurantium) by the Natural Standard Research Collaboration.
Journal of dietary supplements (2013) · Systematic review
Modest thermogenic/metabolic effects
Based on multiple meta-analyses showing 3-6mg/kg optimal dosing. Performance benefits plateau around 200-300mg with increased jitteriness at higher doses.
AI-estimated from published studies. Interpret as directional guidance.
Caffeine has a higher evidence score (9.5/10 vs 4.8/10) and wins in 3 of 3 categories.
For boost daily energy, Caffeine has a higher relevance score (98 vs 45).
Caution: Increased cardiovascular stress, elevated heart rate and blood pressure AVOID combination. Monitor cardiovascular status if used together. Always consult a healthcare provider before combining these supplements.