Whey wins the protein league, and gains plateau near 30 to 35 g a day

Protein supplements are among the most widely bought products in fitness, usually taken alongside resistance training to build muscle mass and strength. Yet three practical questions remain contested: does the type of protein matter, is there a daily dose beyond which extra grams add little, and do older adults respond differently from younger ones? Individual trials are usually too small to answer these questions cleanly, and direct comparisons between protein types are rare. This analysis pooled the trial evidence into a single network so whey, casein, soy, pea, rice, milk and blended proteins could be ranked against each other and against placebo.

The researchers searched six databases through February 2026 for randomised controlled trials comparing a protein supplement with placebo during at least six weeks of supervised resistance training. Thirty-six trials with 1,552 participants across 89 trial arms formed a fully connected network of eight options. A Bayesian analysis ranked the proteins by their effect on lean body mass, and dose-response curves were fitted to test how benefits changed with daily intake. A subgroup analysis compared adults aged 65 and over with younger adults.

Whey protein ranked first for lean body mass, adding 1.24 kg on average versus placebo, followed by milk protein at 1.18 kg and casein at 0.92 kg. The dose-response curve for whey flattened at around 30 to 35 g per day, suggesting little extra gain beyond that intake, though the authors label this estimate exploratory. In adults aged 65 and over, whey's advantage narrowed while casein's ranking improved, but this subgroup rested on only nine trials and the authors warn the ranking changes may be unstable. Plant-based proteins showed smaller effect estimates than dairy proteins, with low to very low certainty and wide credible intervals.

The headline confirms what much of the sports nutrition literature has long suggested: dairy proteins, whey above all, lead the field for lean mass when paired with lifting. The newer contributions are the dose plateau near 30 to 35 g per day and the hint that whey's edge shrinks in older adults, where casein and mixed strategies climb the rankings. Both of those details are flagged as tentative, one exploratory and one built on nine trials. Larger head-to-head trials, particularly of plant proteins and in older lifters, would settle the remaining arguments.

If you lift and use a protein supplement, this is a reason to think whey remains the best-supported choice for lean mass, and that piling in doses far beyond roughly 30 to 35 g a day is unlikely to add much. Older lifters get a specific hint: whey's advantage narrowed after 65, so casein or blended proteins may serve that group just as well. Plant protein users are not ruled out, but the evidence behind those options is weaker and considerably less certain.