Data from 680 individuals revealed that protein supplementation was associated with average increases in fat-free body mass of 0.69 kg, and average increases in leg press strength of 13.5 kg.
“Dietary protein supplementation represents an effective dietary strategy to augment the adaptive response of skeletal muscle to prolonged resistance-type exercise training in healthy younger and older adults,” wrote Dutch researchers in the American Journal of Clinical Nutrition.
“Because the gains in fat-free mass and 1 repetition maximum leg press strength are also observed in an older population, it seems evident that protein supplementation represents an effective and robust strategy to improve the benefits of resistance-type exercise training to support healthy aging.”
Protein supplements are extensively taken by many athletes to build and maintain muscle. While this is generally accepted, the Dutch researchers note that there is “much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations”.
Their meta-analysis is claimed to be the first to examine protein supplementation in relation to the adaptive response of muscle strength, and seeks to resolve any debate over the effectiveness for young and old.
Led by Luc van Loon from Maastricht University Medical Centre, the researchers analyzed data from 22 randomized control trials. The average protein supplement dose was 42 grams per day, and the majority of the studies used whey or milk proteins. Results showed that, compared to placebo, both free-fat mass and leg strength increased.
In addition, protein supplementation was associated with increases in the cross-sectional area of muscle fibers type I and II of 45 and 54%, respectively, said the researchers, but the improvements were only observed in the younger subjects.
“For future investigations, researchers may wish to examine specific variables with respect to the effect of dietary protein supplementation on the adaptive response of skeletal muscle to prolonged resistance-type exercise training,” they wrote.
“The latter may include the effect of the intensity of the exercise sessions, the type or source of dietary protein supplementation, and/or the timing of protein supplementation.”
Source: The American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.112.037556
“Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis”
Authors: N.M. Cermak, P.T. Res, L.C.P.G.M. de Groot, W.H.M. Saris, L.J.C. van Loon