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Aging, protein requirements, and protein turnover
D J Millward1, A Fereday, N Gibson
1Centre for Nutrition and Food Safety, School of Biological Sciences, University of Surrey, Guildford, United Kingdom.
The American Journal of Clinical Nutrition
|October 10, 1997
Summary
Protein needs in older adults may decrease with age, contrary to concerns of increased requirements. Novel studies suggest protein needs fall due to reduced metabolic demand and stable utilization efficiency in healthy elderly individuals.
Area of Science:
- Gerontology
- Nutritional Science
- Metabolism
Background:
- Current protein recommendations for the elderly are based on 1985 guidelines, suggesting no age-related increase in requirements.
- Concerns exist that elderly individuals may have higher protein needs, but existing nitrogen balance data is inconclusive.
Purpose of the Study:
- To systematically evaluate protein requirements and turnover in the elderly using novel tracer methods.
- To compare protein needs in healthy, mobile elderly individuals with established recommendations.
Main Methods:
- Utilized [1-13C]leucine balance studies to measure postabsorptive leucine oxidation and protein utilization efficiency.
- Calculated apparent protein requirements by dividing metabolic demand by protein utilization efficiency.
Main Results:
- Healthy, mobile elderly individuals showed a reduced metabolic demand for protein by approximately one-third.
- No significant impairment in protein utilization efficiency was observed in the elderly.
- Apparent protein requirements decreased with age, from 0.98 +/- 0.17 to 0.69 +/- 0.22 g/kg.
Conclusions:
- The findings support the 1985 protein recommendations, indicating a potential decrease in requirements for healthy, mobile elderly individuals.
- Reduced proteolysis in the postabsorptive state contributes to lower protein needs in aging.
- Further research is needed to assess protein requirements in frail, immobile elderly populations and the utilization of habitual meals.