ABSTRACT: The objective of this study was to verify the protein turnover rates of healthy older persons under a usual protein-rich diet and to compare values to those described in the literature. This cross-sectional study was conducted at Metabolism Unit, Univ. Hospital of the School of Medicine of Ribeirao Preto, Univ. of Sao Paulo, Brazil. In this study, 7 healthy older persons aged 65.4 ± 2.8 y, with BMI 22.7 ± 2.4 kg/m2 and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9-h whole-body 15N-glycine single-dose study was performed after an overnight fast. During the study, each subject received 6 isoenergetic, isonitrogenous meals at 2-h intervals based on their average intake. Ammonium, urea, and total nitrogen were quantified and analyzed by mass spectrometry, with the determination of total protein turnover rates by the 15N-glycine method. The results show that total nitrogen output was 3.2 ± 0.96 g/N and intake 7.7 ± 1 g/N, 15N nitrogen flux was 30.6 ± 6.3 g/9 h. Endogenous nitrogen balance was positive (4.5 g ± 1 g/N in 9 h). In conclusion, the protein turnover of healthy older persons under a usual protein-rich diet is positive during the fed state and has synthesis and degradation rates similar to those previously described in studies involving diet adaptation periods.