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Head-to-head evidence comparison — which supplement is right for you?
Whey Protein wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mostly mechanism / observational
Top outcomes
Verdict
Likely helps
26 of 30 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Soy Protein and Whey Protein have evidence — compare verdict strength side-by-side.
20-40g per serving for muscle (aim ~2-3g leucine); ~25g/day is the level associated with cholesterol lowering
any
Soy protein isolate
20-40g per serving
Post-workout (within 2 hours), Morning, Between meals
Whey Protein Isolate
6-12 weeks
4-12 weeks
Acute
4-8 weeks
24-48 hours post-workout
Immediate
Within hours of consumption
No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise.
Int J Sport Nutr Exerc Metab (2018) · Meta analysis · n=266
Nine studies (266 participants); soy vs whey/animal protein with resistance training ≥6 weeks
Meta-analysis of the effects of soy protein intake on serum lipids.
N Engl J Med (1995) · Meta analysis
38 controlled clinical trials; mean soy intake ~47g/day
Effects of high-quality protein supplementation on cardiovascular risk factors in individuals with metabolic diseases: A systematic review and meta-analysis of randomized controlled trials.
Clin Nutr (2024) · Meta analysis
63 RCTs across soy, milk, whey, and casein protein
Comparative Efficacy of Different Protein Supplements on Muscle Mass, Strength, and Physical Indices of Sarcopenia among Community-Dwelling, Hospitalized or Institutionalized Older Adults Undergoing Resistance Training: A Network Meta-Analysis of Randomized Controlled Trials
Nutrients (2024) · Meta analysis · n=5272
Treatment effects for main outcomes were expressed as standard mean difference (SMD) with 95% confidence interval (CI).
Effects of Whey Protein, Leucine, and Vitamin D Supplementation in Patients with Sarcopenia: A Systematic Review and Meta-Analysis
Nutrients (2023) · Meta analysis · n=637
However, appendicular muscle mass significantly improved in the experimental group compared to the control group.
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength
British Journal of Sports Medicine (2018) · Meta analysis · n=1863
Protein supplementation increases muscle mass gains
Based on multiple meta-analyses with >3000 participants. Effects require concurrent resistance training. Benefits plateau around 30-40g per serving. Isolate forms may reduce digestive issues.
AI-estimated from published studies. Interpret as directional guidance.
Whey Protein has a higher evidence score (9/10 vs 6.5/10) and wins in 2 of 3 categories.
For build strength & muscle, Whey Protein has a higher relevance score (95 vs 56).
No known interactions between Soy Protein and Whey Protein have been documented in our database. However, always consult a healthcare provider before combining supplements.