Macro partitioning
Supplemental protein intake of approximately 5 g/day significantly increases lean body mass, with a plateau in gains between 5-50 g/day and a linear increase in muscle mass for intakes exceeding 50 g/day.
To increase muscle mass, adding just ~5 grams of protein daily (e.g., one egg or a cup of milk) can be effective, even without exercise. If you are engaging in resistance training or seeking maximal hypertrophy, increasing supplemental protein beyond 50 grams per day may continue to drive linear increases in lean body mass. This applies to diverse populations, including the elderly and those without serious illness.
lean body mass significantly improved with about 5 g/day of supplementary protein intake; this effect further increased with > 50 g/day supplementary protein intake.
Why this rating
Large sample size (5411 subjects) and rigorous meta-analysis of RCTs, though heterogeneity was high (I2=74%).
Source
Dose–response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomized controlled trials
Ryoichi Tagawa et al. · Nutrition Reviews · 2020
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