Lysine requirement of healthy, school-aged Indian children determined by the indicator amino acid oxidation technique

We recently reported the lysine requirement of school-aged children living in Canada consuming a mixed diet to be 35 mg x [kg.sup.-1] x [d.sup.-1]. Because the majority of children in the world live on cereal-based diets in developing countries, we measured the daily lysine requirement in healthy children living in India and consuming a mostly cereal-based diet. Our objective in this study was to determine the lysine requirement in healthy, school-aged children in the developing world by using the indicator amino acid oxidation method with L-[1-[sup.13]C] phenylalanine. Six healthy, school-aged children consumed 7 levels of lysine (5, 15, 25, 35, 50, 65, and 80 mg x [kg.sup.-1] x [d.sup.-1]) each in a random order along with an amino acid mixture providing energy and protein intakes of 1.7 x resting energy expenditure and 1.5 g x [kg.sup.-1] x [d.sup.-1], respectively. The mean lysine requirement was determined by applying a 2-phase linear regression crossover analysis on tracer oxidation ([F.sup.13]C[O.sub.2]) data, which identified a breakpoint (requirement) at minimal [F.sup.13]C[O.sub.2] in response to the graded lysine intakes. The mean lysine requirements with the upper 95% CI for children were determined to be 33.5 and 46.6 mg x [kg.sup.-1] x [d.sup.- 1], respectively, by breakpoint analysis of the [F.sup.13]C[O.sub.2] data. The mean lysine requirements of Indian children were almost identical to that of Canadian children (35 mg x [kg.sup.-1]x [d.sup.-1]). There is no evidence for any adaptation in lysine requirements in children from developing countries such as India. J. Nutr. 140: 54-59, 2010. doi: 10.3945/jn.109.113357.