Whey and Pea (NUTRALYS® S85 Plus), but Not Collagen, Protein Supplementation Beyond the RDA Enhances Integrated Myofibrillar Protein Synthesis in Older Men

Objectives: Older individuals display a diminished muscle protein synthesis (MPS) response to protein ingestion, referred to as age-related anabolic resistance, which contributes to the progression of age-related muscle loss. We hypothesized that the recommended dietary allowance (RDA; 0.8 g protein/kg/d) for protein would be insufficient to overcome anabolic resistance. We aimed to determine the impact of divergent supplemental protein sources consumed at lower protein-containing meals (breakfast and lunch) on integrated rates of MPS in older individuals. Methods: Thirty-one healthy older men (72 ± 4 y) underwent a controlled diet with protein intake set at the RDA – phase (CON; days 1-7). In a double-blind, randomized controlled fashion, participants were assigned to consume an additional 50g (2x25g) of Whey (WHEY, n=10, Sureprotein™ WPC450) Pea (PEA, n=11, NUTRALYS® S85 Plus), or collagen (COLL, n=10, Bodybalance®) protein daily (25 g/meal at breakfast and lunch) during the supplemental phase (SUPP; days 8-15). Deuterated water ingestion and muscle biopsies enrichment were used to assess integrated MPS and acute postprandial anabolic signaling. Postprandial blood samples were collected to determine feeding-induced aminoacidemia. Results: Integrated-MPS was increased during SUPP with WHEY (1.59 ± 0.11 %/d, p=0.001) and PEA (1.58 ± 0.14 %/d, p=0.001) when compared with RDA (1.46 ± 0.09 %/d WHEY; 1.46 ± 0.10 %/d PEA); however, it remained unchanged with COLL. Supplemental protein was sufficient to overcome anabolic signaling deficits (mTORC1 and rpS6), corroborating the greater postprandial aminoacidemia. Conclusions: Our findings demonstrate that supplemental protein over the current RDA enhanced anabolic signalling and integrated MPS in older men. The source of additional protein and/or the timing of its ingestion may be an important consideration in overcoming age-related anabolic resistance. Funding Sources: J.M. and C.L. were supported by postdoctoral fellowships from the Canadian Institute of Health Research (CIHR). B.S.C. was supported by a Canadian Graduate Scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). This study was supported by a grant from Roquette Frères awarded to S.M.P.