The Dietary Protein Requirements of Younger and Older Adults

By Richard Shank

A new study suggests that the dietary protein requirements for younger and older adults are the same. Little was previously known about the daily protein requirements for older men and women, and the research that had previously attempted to estimate these requirements provided an uneven picture.

Aging is associated with various metabolic and physiologic changes. These changes can include fluctuations in body composition (e.g. the loss of muscle mass), declines in physical activity, diminished physical functioning, food intake, and increased frequency of disease. The current Estimated Average Requirement (EAR) (.66 g) and Recommended Allowance (RDA) (.88 g) of protein have been assumed to stay constant after the age of 19 years old. Given the assumed metabolic and physiologic changes, the researchers felt justified in their need to confirm the scientific foundations of the dietary recommendations.

Previous research had either failed to include both men and women as participants, or had not compared the protein requirements of older and younger adults. The current daily protein intake recommendations for older adults have been based on short-sighted data. The study attempted to validate the previous recommendations by providing more meaningful comparisons between both men and women, young and old.

Fifty-eight individuals were recruited to participate in this study, including 3 younger men, 21 younger women, 12 older men, and 12 older women. Each subject completed a pre-study evaluation that included their medical history, blood and urine chemistry, and a resting-state electrocardiogram. Each subject completed three 18 day periods of strict dietary control, with a minimum of one week of normal eating between the trials. Each daily menu was customized to control protein intake. During each day of the trial, body composition was measured. Once per trial period, food, urine, blood, and stool collections were taken and a nitrogen level analysis was performed on them.

The findings of this study confirm the current recommendations. Older and younger adults do need similar amounts of protein on a daily basis and the uncertain recommendations pertaining to the amount of protein is statistically accurate.

Source: Campbell, W., Johnson, C., McCabe, G. et al. 2008. American Journal of Clinical Nursing 88:1322-1329.

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