Human protein requirements: assessment of the adequacy of the current Recommended Dietary Allowance for dietary protein in elderly men and women.

A continuous 30-day metabolic N balance study was conducted in seven elderly men (75 +/- 4 yr) and eight elderly women (78 +/- 9 yr) to evaluate the current protein Recommended Dietary Allowance for older men and women. The subjects received a diet providing 0.8 g egg protein (N x 6.25) kg-1 day-1. Energy intake computed to meet needs averaged 32 and 29 kcal kg-1 day-1 for males and females, respectively. N balances, including an estimate for integumental and other miscellaneous losses, were determined for the last 5 days of three consecutive 10-day diet periods and blood biochemical measurements were made at the end of each diet period. Three of seven males and four of eight females were not in body N balance during the final 5 days of the 30-day period. These N balance data indicate that 0.8 g egg protein kg-1 day-1 is not sufficient to achieve N equilibrium in a majority of subjects older than 70 yr and confirm the results and conclusions of a previous, short-term N balance study (Uauy et al., Am J Clin Nutr 1978;31:779-85). Hence, where energy intake approximates requirement, the current Recommended Dietary Allowance is not adequate for a majority of male and female subjects age 70 yr and above.