AN INITIAL ASSESSMENT, USING 24-H [C-13]LEUCINE KINETICS, OF THE LYSINE REQUIREMENT OF HEALTHY ADULT INDIAN SUBJECTS

The international 1985 FAO/WHO/UNU upper dietary requirement for lysin e of 12 mg.kg(-1).d(-1) may be inadequate for healthy Indian adults. T o test this, we used a modified indicator amino acid oxidation techniq ue to assess the adequacy of lysine intakes of 12 and 28 mg.kg(-1).d(- 1). Seven healthy, male, Indian subjects were studied during each of t wo randomly assigned 6-d periods while receiving an otherwise adequate diet based on an L-amino acid mixture. Beginning at 1800 on day 6 of the diet, a 24-h infusion protocol in which a [C-13]leucine tracer was administered intravenously was used to assess leucine oxidation and d aily leucine balance at each test lysine intake. Mean 24-h leucine oxi dation was 54.7 compared with 46.9 mg.kg(-1).d(-1) (P < 0.05) and mean 24-h leucine balances were -4.1 and 3.5 mg.kg(-1).d(-1) (P < 0.05) fo r lysine intakes of 12 and 28 mg, respectively. Leucine balances were significantly negative (0.025 < P < 0.05) with the 12-mg lysine intake and not significantly different (P > 0.10) from zero or equilibrium w ith the 28-mg intake. These findings indicate that the international r equirement for lysine appears to be inadequate to maintain body amino acid homeostasis and function in apparently healthy subjects character istic of the south Asia region. They further indicate that our previou sly proposed, tentative lysine requirement of 30 mg.kg(-1).d(-1) is pr obably adequate for this population.