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Cited by 397Muscle metabolism and nutritionNutrition and Health in AgingBody Composition Measurement Techniques

The Recommended Dietary Allowance for Protein May Not Be Adequate for Older People to Maintain Skeletal Muscle

Campbell, W. W., Trappe, T. A., Wolfe, R. R., Evans, W. J.·2001·The Journals of Gerontology Series A: Biological Sciences and Medical Sciences
DOI 10.1093/gerona/56.6.m373
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Abstract

BACKGROUND: Inadequate dietary protein intake results in loss of skeletal muscle mass. Some shorter-term nitrogen balance studies suggest that the Recommended Dietary Allowance (RDA) of protein may not be adequate for older people. The aim of this study was to assess the adequacy of the RDA of protein for older people by examining longer-term responses in urinary nitrogen excretion, whole-body protein metabolism, whole-body composition, and mid-thigh muscle area. METHODS: This was a 14-week precisely controlled diet study. Ten healthy, ambulatory men and women, aged 55 to 77 years, were provided eucaloric diets that contained 0.8 g protein.kg(-1).day(-1). The study was conducted at a General Clinical Research Center using an outpatient setting for 11 weeks and an inpatient setting for 3 weeks. The main outcome measures included urinary nitrogen excretion, postabsorptive and postprandial whole-body leucine kinetics via infusion of L-[1-(13)C]-leucine, whole-body density via hydrostatic weighing, total body water via deuterium oxide dilution, and mid-thigh muscle area via computed tomography scans. RESULTS: Mean urinary nitrogen excretion decreased over time from Weeks 2 to 8 to 14 (p =.025). At Week 14, compared with Week 2, there were no changes in postabsorptive or postprandial leucine kinetics (turnover, oxidation, incorporation into protein via synthesis, release via breakdown, or balance). Whole-body composition (% body fat, fat-free mass, and protein + mineral mass) did not change over time in these weight-stable subjects. Mid-thigh muscle area was decreased by -1.7 +/- 0.6 cm(2) (p =.019) at Week 14 compared with Week 2. The loss of mid-thigh muscle area was associated with the decrease in urinary nitrogen excretion (Spearman r =.83, p =.010). CONCLUSIONS: The maintenance of whole-body leucine metabolism and whole-body composition is generally consistent with a successful adaptation to the RDA for protein. However, the decrease in mid-thigh muscle area and the association with decreased urinary nitrogen excretion are consistent with a metabolic accommodation. These results suggest that the RDA for protein may not be adequate to completely meet the metabolic and physiological needs of virtually all older people.

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  • In one intervention study, consuming the recommended dietary allowance for protein resulted in loss of mid-thigh muscle area over 14 weeks in healthy older adults (n = 10).

    “In one intervention study of intermediate length, Campbell et al 21 found that consuming the RDA for protein resulted in the loss of mid-thigh muscle area over a 14-week period in healthy older adults (n ¼ 10).”

    From Evidence-Based Recommendations for Optimal Dietary Protein Intake in Older People: A Position Paper From the PROT-AGE Study Group (2013) · cites this paper as [21]

  • In that study, whole body composition and weight did not change, but mid-thigh muscle area significantly decreased (P = .019), suggesting metabolic adaptation and that the recommended dietary allowance was not adequate.

    “Although whole body composition (% body fat, fat-free mass, and protein þ mineral mass) and weight did not change over the course of the intervention, mid-thigh muscle area was significantly decreased (P ¼ .019),suggesting that metabolic adaptation may have occurred and the RDA for protein was not adequate to meet the metabolic and physiological needs of these individuals.”

    From Evidence-Based Recommendations for Optimal Dietary Protein Intake in Older People: A Position Paper From the PROT-AGE Study Group (2013) · cites this paper as [21]

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Authors
Campbell, W. W., Trappe, T. A., Wolfe, R. R., & Evans, W. J.
Affiliations
University of Arkansas for Medical Sciences (US)
Corresponding author
Campbell, W. W.
ORCID
Venue
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences
Publisher
Oxford University Press (OUP)
Published
2001-06-01
Volume
56
Issue
6
Pages
M373-M380
ISSN
  • 1079-5006 (ISSN-L)
  • 1758-535X
DOI
10.1093/gerona/56.6.m373
OpenAlex
W2157896915
Cited by
397
References
3
Citations by year
2026: 3 · 2025: 4 · 2024: 8 · 2023: 6 · 2022: 12 · 2021: 17 · 2020: 16 · 2019: 14 · 2018: 25 · 2017: 23 · 2016: 20 · 2015: 16 · 2014: 22 · 2013: 24 · 2012: 23
FWCI
4.09
Type
journal article
Language
en
Open access
closed
Locations
  • The Journals of Gerontology Series A (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Deutsches Krebsforschungszentrum
  • Rural Development Administration
  • National Institutes of Health (7r01ag011811-07)
  • National Institute on Aging (1 R29 AG13409, AG11811, R29AG013409)
  • National Center for Research Resources (MO1 RR10732, M01RR010732)
  • NIH Clinical Center
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Physiology › Nutrition and Health in Aging
  • Health Sciences › Medicine › Physiology › Body Composition Measurement Techniques
Keywords
protein intake, RDA, older adults, sarcopenia, skeletal muscle mass, urinary nitrogen excretion, whole body protein metabolism, leucine kinetics, body composition, fat-free mass, metabolic adaptation
MeSH terms
Aged, Aging, Body Composition, Dietary Proteins, Female, Humans, Leucine, Male, Middle Aged, Nitrogen, Thigh, Muscle, Skeletal, Nutrition Policy

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