Study of Dietary Reference Intakes of Protein for Chinese Male Youths with Labeled Leucine and Lysine

Abstract

Six experimental diets of different designed protein levels in Chinese diet were consumed by 20 healthy male youths divided into two groups in three continuing 7‐day cycle separately. After 5 days¡ adaptation, intravenous transfusion of stable isotope labeled leucine (13C) and lysine(15N) was administrated in 3 hours. The abundances of 13CO2 and 15N‐urea in the samples were determined, then computed the flux and oxidation rate of leucine and lysine. We explored the protein requirement by constructing the two phase linear regression equations between protein intakes and amino acid oxidation rate and determined the regression curve breakpoint. We adopted the largest value of 0.83g/kg/d among all three protein requirements determined by three regression curves as the average physiological requirements for our study population, and the recommended nutrient intake of 0.96g/kg/d for protein.