Effect of Ingested Beef Quantity on Daily Muscle Protein Synthesis During Resistance Training in Middle-aged Adults (P08-068-19)

Abstract

Objectives High protein diets (>1.6 g/kg/d) are thought to maximize daily myofibrillar protein synthesis (MPS) rates to resistance exercise training. Current research has focused on isolated protein sources to stimulate MPS disregarding other nutritional factors within a healthy diet. Therefore, we examined the impact of dietary counseling underlining food-focused healthy eating patterns equally distributing protein through high-quality sources at the Recommended Daily Allowance (RDA) or in excess on resistance exercise mediated daily rates of MPS in middle-aged adults. Methods Nineteen healthy middle-aged adults (11 M, 8F, 48 ± 7 y, BMI: 28.9 ± 3.7 kg/m2, 7451 ± 4957 steps/d) were randomized to consume protein at the RDA (0.8–1.0 g/kg/d, n = 10) or twice the RDA (2 × RDA, 1.6–1.8 g/kg/d, n = 9) for 2 weeks. Participants were counseled to equally distribute protein between meals and consumed either 15 g (RDA) or 30 g (2 × RDA) protein from lean beef in immediately post-exercise and nightly. Week 0 (−7 to 0 d) served as a dietary habituation, and week 1 (1–8 d) included whole body resistance exercise sessions (3/wk) with the dietary intervention. On 0 d, participants ingested 5 mL/kg over 10.5 h of deuterated water (2H2O) for deuterium enrichment of body water, with maintenance daily doses of 0.625 mL/kg/d 2H2O for days 1–8. Repeated saliva and muscle biopsies from the vastus lateralis were collected throughout the 1-week intervention to assess daily rates of MPS. Results The 2 × RDA group (1.6 ± 0.4 g/kg/d) consumed significantly more protein than the RDA group (1.0 ± 0.4 g/kg/d, P = 0.01). Steady-state body water enrichment was not different (P = 0.94) between the 2 × RDA (0.9 ± 0.3%) or RDA (0.9 ± 0.1%) groups. Daily MPS was not different (P = 0.43) between RDA (0.91 ± 0.2%/d) and 2 × RDA groups (1.13 ± 0.6%/d) during the 1-week intervention. Conclusions Daily MPS with resistance exercise training is not altered by a more protein-dense diet when at least the RDA is consumed in middle-aged adults. Our data suggest that multi-component nutritional strategies focusing on protein quality, distribution, and timing may supersede the importance of only considering total quantity to support early hypertrophic protein remodeling with resistance exercise. Funding Sources This work was supported by funds provided by the National Cattleman's Beef Association.