Reevaluation of the protein requirement in Chinese elderly adults without sarcopenia with the indicator amino acid oxidation technique

It is now generally believed that elderly may have slightly higher dietary protein requirements than those of the young-middle-aged adults. We have previously conducted related studies by the indicator amino acid oxidation (IAAO) technique, but more research data are needed to revise the protein requirements of the elderly. The main objective was to reevaluate the dietary protein requirements of healthy Chinese adults (65-80 years) without sarcopenia by using the IAAO technique. Nine healthy adult men and seven healthy adult women participated in the study, with protein intakes ranging from 0 center dot 1 to 1 center dot 8 g/(kg center dot d). Diets that delivered energy at a 1 center dot 5 resting energy expenditure were isocaloric. The amounts of phenylalanine and tyrosine needed to remain constant for each protein dosage. By applying a nonlinear mixed-effects model analysis on the F13CO2 data, which revealed a breakpoint in F13CO2 in response to graded protein intakes, the mean protein requirement was calculated. The mean estimated average requirement (EAR) for healthy elderly Chinese adults without sarcopenia was determined to be 0 center dot 94 g/(kg center dot d). The protein recommended nutrient intake (RNI) determined using various derivation approaches ranged from 1 center dot 13 to 1 center dot 36 g/(kg center dot d). The EAR for Chinese adults without sarcopenia aged 65-80 years in this study is 6 center dot 8 % higher than the current recommended EAR (0 center dot 88 g/(kg center dot d)). The RNI derived using various derivation approaches are all greater than the current RNI (0 center dot 98 g/(kg center dot d)). This trial was registered with the Chinese clinical trial registry as ChiCTR2200061382.