Sarcopenia is characterized by age-related loss of muscle mass and strength. Energy restriction (ER) delays fiber loss as it limits the damaging effects of reactive oxygen species on muscle. Insufficient protein intake during ER seems to affect muscle mass and function. Walrand and colleagues hypothesized that consuming fast-digested proteins, such as whey protein (WP), could improve muscle protein synthesis and muscle strength in aged ER models.

Investigators thus evaluated the effect of WP or casein (CAS, slow protein) on muscle mass, protein synthesis and strength in experimental models fed for 5 months either ad libitum (AL) or a 40% protein and energy-restricted (PER) or 40% AL-isonitrogenous ER diet.

The nitrogen balance was reduced in PER-CAS models only (-48 % vs. AL-CAS). WP stimulated muscle protein synthesis rates in comparison with CAS in all the studied groups (+21, +37 and +34% in AL, PER and ER conditions, respectively; Fig. 1). Muscle strength was higher in ER models than in AL models (+23 and +12% for WP and CAS, respectively). Muscle performance was also greater in ER rats fed WP compared to ER-CAS rats.

Long-term ER combined with maintained WP consumption was thus found to have a beneficial impact on muscle protein synthesis rate and function during ageing.

Fig. 1. Increase in muscle protein synthesis rate in whey protein supplemented models vs. casein group

Reference

1. Walrand S, Zangarelli A, Guillet C, et al. Effect of fast dietary proteins on muscle protein synthesis rate and muscle strength in ad libitum-fed and energy-restricted old rats. Br J Nutr. 2011 Dec;106(11):1683-90.