Macro partitioning
Compared with animal protein, plant protein results in lower muscle mass, with a stronger negative effect observed in younger adults (<60 years) than in older adults (≥60 years).
If your goal is maximizing muscle mass, animal protein may offer a slight advantage over plant protein, particularly in younger adults. However, the difference is small, and plant protein is still effective. Focus on getting enough total protein and combining plant sources if possible.
Compared with animal protein, plant protein resulted in lower muscle mass following the intervention (SMD = –0.20; 95% CI: –0.37, –0.03; P = .02), with stronger effects in younger (<60 years; SMD = –0.20; 95% CI: –0.37, –0.03; P = .02) than in older (≥60 years; SMD = –0.05; 95% CI: –0.32, 0.23; P = .74) adults.
Why this rating
Based on a systematic review and meta-analysis of 30 eligible RCTs, though heterogeneity exists.
Source
Effect of Plant Versus Animal Protein on Muscle Mass, Strength, Physical Performance, and Sarcopenia: A Systematic Review and Meta-analysis of Randomized Controlled Trials
Rachel Reid-McCann et al. · Nutrition Reviews · 2025
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