A moderate serving of high-quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects.

Full Abstract

Ingestion of sufficient dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. Elderly people are often at increased risk for protein-energy malnutrition, sarcopenia, and a diminished quality of life. This study sought to compare changes in muscle protein synthesis and anabolic efficiency in response to a single moderate serving (113 g; 220 kcal; 30 g protein) or large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Venous blood and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion (0.08 mumol/kg/min) of L-[ring-(13)C(6)] phenylalanine in healthy young (n=17; 34+/-3 years) and elderly (n=17; 68+/-2 years) individuals. Mixed muscle fractional synthesis rate was calculated during a 3-hour postabsorptive period and for 5 hours after meal ingestion. Data were analyzed using a two-way repeated measures analysis of variance with Tukey's pairwise comparisons. A 113-g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a threefold increase in protein and energy content, there was no further increase in protein synthesis after ingestion of 340 g lean beef in either age group. Ingestion of more than 30 g protein in a single meal does not further enhance the stimulation of muscle protein synthesis in young and elderly.

Author information

Author/s: Symons, T Brock (TB); Sheffield-Moore, Melinda (M); Wolfe, Robert R (RR); Paddon-Jones, Douglas (D);

Affiliation: Graduate Center for Gerontology, University of Kentucky, Lexington, USA.

Grants: M01 RR-00073 (Agency:NCRR NIH HHS) ; P30 AG17231 (Agency:NIA NIH HHS)

Journal and publication information

Publication Type: Comparative Study; Journal Article; Randomized Controlled Trial; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Journal of the American Dietetic Association (J Am Diet Assoc), published in United States. (Language: eng)

Reference: 2009-Sep; vol 109 (issue 9) : pp 1582-6

Dates: Created 2009/08/24; Completed 2009/09/22;

PMID: 19699838, status: MEDLINE (last retrieval date: 9/22/2009, IMS Date: )

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