Aging does not impair the anabolic response to a protein-rich meal

T. Brock Symons, Scott E. Schutzler, Tara L. Cocke, David L. Chinkes, Robert R. Wolfe, Douglas Paddon-Jones

    Research output: Contribution to journalArticlepeer-review

    182 Scopus citations


    Background: Sarcopenia is a debilitating condition afflicting the elderly that may be facilitated by insufficient or ineffectual intake of dietary protein. We previously showed that free-form essential amino acids acutely stimulate muscle protein synthesis in both the young and the elderly. However, the ability of an actual protein-rich food to stimulate anabolism in the young and the elderly has not been explored. Objective: We aimed to characterize changes in plasma amino acid concentrations and to quantify muscle protein synthesis in healthy young (41 ± 8 y old; n = 10) and elderly (70 ± 5 y old; n = 10) persons after ingestion of a 113-g (4-oz) serving of lean beef. Design: Venous blood samples and vastus lateralis muscle biopsy samples were obtained during a primed (2.0 μmol/kg) constant infusion (0.08 μmol·kg-1·min-1) of L-[ring- 13C6] phenylalanine. Plasma amino acid concentrations were measured and a mixed-muscle fractional synthesis rate (FSR) was calculated during the premeal period and for 5 h after beef ingestion. Results: Mixed-muscle FSR increased by ≈51% in both the elderly (mean ± SE measurements: 0.072 ± 0.004%/h and 0.108 ± 0.006%/h before and after the meal, respectively) and the young (0.074 ± 0.005%/h and 0.113 ± 0.005%/h before and after the meal, respectively) after beef ingestion (P < 0.001). Plasma amino acid concentrations peaked at ≈100 min after beef ingestion in both age groups but were substantially higher in the elderly (2185 ± 134 nmol/mL compared with 1403 ± 96 nmol/mL; P < 0.001). Conclusion: Despite differences in the concentration of amino acids in the plasma precursor pool, aging does not impair the ability to acutely synthesize muscle protein after ingestion of a common protein-rich food.

    Original languageEnglish (US)
    Pages (from-to)451-456
    Number of pages6
    JournalAmerican Journal of Clinical Nutrition
    Issue number2
    StatePublished - Aug 1 2007


    • Amino acids
    • Beef
    • Diet
    • Nutrition
    • Sarcopenia
    • Stable isotopes

    ASJC Scopus subject areas

    • Medicine (miscellaneous)
    • Food Science


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