Effect of Soy-Dairy Protein Blend Ingestion on Post-Exercise Muscle mTORC1 Signaling and Protein Synthesis in Older Adults

PurposeOur previous work demonstrated that a soy-dairy protein blend can prolong aminoacidemia and muscle protein synthesis in young adults following high intensity resistance exercise. The current work investigated the effect of the same soy-dairy protein blend in older individuals who commonly develop anabolic resistance and sarcopenia. We hypothesized that a soy-dairy protein blend (whey, soy and casein) would prolong aminoacidemia resulting in enhanced mTORC1 signaling and muscle protein anabolism as compared to a whey protein isolate (WPI) alone. MethodsThe study population for this double-blind randomized controlled trial included recreationally active men 55–75 years of age. The subjects consumed 30g of WPI or 30g of a soy-dairy protein blend (25% soy, 25% whey, and 50% casein) one hour following leg extension exercise (8 sets of 10 repetitions at 70% 1RM). Amino acid concentrations as well as basal and post-exercise muscle protein turnover (breakdown and synthesis) were measured using stable isoto...