Quantity of dietary protein, but not pattern of intake, affects net protein accretion in older adults (272.4)

Abstract

We examined 16‐h whole body protein turnover [protein synthesis (PS), breakdown (PB), and net balance (NB), expressed as delta changes from the fasted state] in four permutations: a level of protein intake of 0.8g/kg/day (1RDA) or 1.5g/kg/day (2RDA) with an uneven [U: 15/20/65%)] or even distribution patterns of intake (E: 33/33/33%) for breakfast, lunch, & dinner of intake over the day. Twenty healthy older subjects were randomly assigned into one of 4 groups: 1RDA‐U, 1RDA‐E, 2RDA‐U, or 2RDA‐E, and were studied with primed continuous infusions of ring‐[2H5]phenylalanine & ring‐[2H2]tyrosine on day 4 following 3 days of diet habituation. Positive NB was achieved at both protein levels, but NB was significantly greater in 2RDA vs. 1RDA [NB: 94.75 ± 6.01 vs. 58.86 ± 4.91 g protein/kg/750min; p = 0.0001], without effects of distribution on NB. The greater NB was due to the higher PS with 2RDA vs. 1RDA [PS: 15.40 ± 4.84 vs. ‐17.98 ± 8.44 g protein/kg/750min; p = 0.0018]. PS was significantly correlated with delta changes of mean plasma concentrations of leucine from the fasted state (R2 = 0.51, p = 0.0004). We conclude that in the context of mixed meals whole body net protein accretion is greater with protein intake above recommended dietary allowance (0.8 g protein/kg/day), regardless of protein intake pattern, primarily through increased protein synthesis.Grant Funding Source: Supported by Dairy Research Institute and Award Number UL1TR000039 and KL2TR000063 (NCATS and NIH)