Lysine requirements of chronically undernourished adult indian men, measured by a 24-h indicator amino acid oxidation and balance technique

Abstract

Background: In earlier studies with well-nourished subjects that used a 24-h indicator amino acid oxidation or balance approach, we concluded that the 1985 FAO/WHO/UNU requirement for lysine (12 mg · kg-1 · d-1) was inadequate for healthy South Asian subjects and proposed a tentative requirement of 30 mg · kg-1 · kg-1. Objective: We assessed whether chronic undernutrition, with low habitual dietary protein and lysine intakes, leads to changed lysine requirements. Design: Twenty-seven otherwise clinically healthy, chronically undernourished Indian men were studied during 2 randomly assigned 7-d diet periods supplying 12 and 30, 18 and 36, or 24 and 42 mg lysiney · kg-1 · d-1, based on an L-amino acid diet. The subjects' leucine intake was 40 mg · kg-1 · d-1. At 1800 on day 6, a 24-h intravenous [13C]leucine tracer-infusion protocol was conducted to assess leucine oxidation and daily leucine balance at each test lysine intake. Results: A breakpoint was not identified in the lysine intake-leucine oxidation or balance response over the range of intakes studied. Mixed-models linear regression analysis indicated a mean requirement of 44 mg lysine · kg-1 · d-1 (95% CI: 36, 63) for the lysine intake-leucine balance relation. Conclusions: The mean lysine requirement in chronically undernourished men is estimated to be higher than the value of 30 mg · kg-1 · d-1 proposed for well-nourished individuals. This may be related to body-composition differences. It also suggests that these subjects have not elicited a metabolic adaptation in response to their habitually low lysine intakes by substantially improving their efficiency of dietary lysine utilization.