TAP reading note: A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults
Across 49 trials, supplementation added an average 0.30 kg of fat-free mass (95% CI 0.09–0.52) and 2.49 kg in one-repetition-maximum strength (0.64–4.33) to resistance-training gains. The estimated daily-intake breakpoint was 1.62 g/kg/day, with considerable uncertainty.
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What the study found
Across 49 trials, supplementation added an average 0.30 kg of fat-free mass (95% CI 0.09–0.52) and 2.49 kg in one-repetition-maximum strength (0.64–4.33) to resistance-training gains. The estimated daily-intake breakpoint was 1.62 g/kg/day, with considerable uncertainty.
Scope & limitations
49 randomized trials; 1,863 healthy adults, with a mixture of ages and training histories. Energy-restricted participants were excluded.
The breakpoint analysis used 42 study arms and 723 participants: 95% CI 1.03–2.20 g/kg/day; the segmented model comparison did not reach conventional significance (p=.079). This is a study-level estimate, not an individual requirement, a safety ceiling or a proven optimum. Women and older adults had less evidence.
Population & sample
49 randomized trials; 1,863 healthy adults, with a mixture of ages and training histories. Energy-restricted participants were excluded.
Exposure or intervention
Protein supplements plus resistance training versus training with placebo or no supplement; food-based and isolated-protein interventions were included.
Outcomes
Changes in fat-free mass, one-repetition-maximum strength and muscle size; these are not everyday fatigue or whole-body recovery measures.
Time frame
Training lasted at least six weeks; publications spanned 1962–2016. Published online in 2017, in the 2018 journal issue.
Research funding
Stuart M. Phillips acknowledged Canada Research Chairs, Canadian Institutes of Health Research and Natural Sciences and Engineering Research Council of Canada support.
Research conflicts of interest
Phillips disclosed grants, travel and presentation honoraria from the US National Dairy Council, which also supported trials included in the analysis.
Reading scope
PMC full text: eligibility, pooled results, breakpoint analysis and Figure 5, limitations and declarations. Individual trial data and all supplementary analyses were not independently reanalysed.
References
Publication record
TAP-RDN-0081 · v1.0 · English
Author: TAP Editorial Team ·
The Allostasis Project is founded and supported by Resilio.
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- v1.0 · 2026-11-13