Daily requirement for and splanchnic uptake of leucine in healthy adult Indians

Abstract

Background: The 1985 FAO/WHO/UNU requirement for leucine is too low according to tracer-derived estimates of leucine oxidation and balance in adults from developed regions. Objective: The leucine requirement in populations in developing countries was assessed with use of the 24-h tracer balance method and on the basis of nitrogen balances. Design: Twenty healthy Indian men were studied during their consumption for 6 d of 2 L-amino acid diets that supplied either 14 and 30 (n = 10) or 22 and 40 (n = 10) mg leucine·kg-1·d-1 in random order. At 1800 on day 7, a 24-h constant intravenous [13C]leucine tracer-infusion protocol was conducted to determine leucine oxidation and daily leucine balance. During the intake of 40 mg leucine/d, [2H3]leucine was given orally to assess the splanchnic uptake of leucine. Results: Mean 24-h leucine oxidation rates were 29.8, 30.6, 33.6, and 39.3 mg·kg-1·d-1 at leucine intakes of 14, 22, 30, and 40 mg·kg-1·d-1, respectively; daily leucine balances were -16.5, -9.0, -3.3, and 0.5 mg·kg-1·d-1, respectively. Mixed-models linear regression of balance against leucine intake resulted in a zero balance at a leucine intake of 37.3 mg·kg-1·d-1. Nitrogen balances were -12.7, -17.9, -3.9, and 1.0 mg·kg-1·d-1 at leucine intakes of 14, 22, 30, and 40 mg·kg-1·d-1. Regression of nitrogen balance against intake resulted in a zero balance at a leucine intake of 37.6 mg·kg-1·d-1. The first-pass splanchnic uptake of leucine was 45.7% and 33.9% in the fasted and fed periods, respectively. Conclusion: A tentative mean leucine requirement of 40 mg·kg-1·d-1 is proposed for healthy Indian adults, as it is for Western subjects.