Protein supplements and resistance training: What works best for older adults? Original paper

In this network meta-analysis, supplementation with soy, milk, or whey protein was effective for improving muscle mass, muscle strength, and physical mobility indices in older adults who were undergoing resistance training.

The study examined the effect of 6 protein sources (milk, meat, casein, peanuts, soy protein, and whey protein) combined with resistance training on muscle mass, muscle strength, and physical mobility indices (walking speed, chair rise, Timed Up and Go test, and the Short Physical Performance Battery).

A total of 5,272 older adults (average ages of 47–89; 58% women and 42% men), including hospitalized, institutionalized, and community-dwelling older adults.

A network meta-analysis of 78 ​​randomized controlled trials was performed. The studies were mainly conducted in Western countries (77%), and the remaining studies were conducted in Asia. The study durations ranged from 2 weeks to 12 months.

The daily doses of supplemental protein ranged from 10 to 60 grams when ingested during resistance training and from 10 to 80 grams when consumed after resistance training. In studies in which protein supplementation was combined with resistance training, the participants performed resistance training for 2–7 sessions per week. The training load was moderate to high with a median intensity of 75% of the 1-repetition maximum or a median rating of perceived exertion (RPE) of 7 (out of 10).

A subgroup analysis was conducted to evaluate whether the outcomes were influenced by the participants’ sex, health conditions, and supplementation dosage.

Soy, milk, and whey proteins were most effective for improving muscle mass and strength when combined with resistance training (all with large effect sizes). Protein supplementation without resistance exercise was only effective for improving handgrip strength when consuming soy and whey protein, with a moderate and large effect size, respectively.

Physical mobility indices were improved when resistance training was complemented with milk or whey protein supplementation (3 of 4 indices improved) and (to a lesser extent) soy protein supplementation (1 of 4 indices improved).

The participants' baseline health status moderated the effects on muscle mass and handgrip strength, with healthier participants exhibiting better responses to protein supplementation combined with resistance training. The efficacy of the intervention on muscle mass also varied by sex, with men showing slightly more pronounced benefits than women. Higher doses of protein supplementation were also linked to greater improvements in muscle mass and strength, suggesting a dose-response relationship.

Although resistance training alone is effective for improving muscle mass and strength, this study highlights the efficacy of complementing resistance training with protein supplementation for improved muscle health outcomes.

However, the study also has several limitations. The included studies varied widely in participant characteristics and settings (community-dwelling, hospitalized, institutionalized participants), which might affect the generalizability of the findings. Additionally, differences in resistance training protocols across studies could influence the efficacy of the protein supplementation.

The varying quality of the included studies, with some having high risks of bias, reduces confidence in this study’s outcomes.