Lysine requirements of healthy adult Indian subjects, measured by an indicator amino acid balance technique

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Abstract
Background: In an earlier study, using a modification of the indicator amino acid oxidation approach, we concluded that the 1985 FAO/WHO/UNU–proposed lysine requirement of 12 mg•kg−1•d−1 is likely inadequate to maintain body amino acid homeostasis in apparently healthy south Asian subjects and that our proposed requirement of 30 mg•kg−1•d−1 is more appropriate. Objective: We assessed the lysine requirement in a similar population by using 4 test lysine intakes (12, 20, 28, and 36 mg•kg−1•d−1) with an indicator amino acid balance approach. Design: Sixteen healthy male Indians were studied during each of 2 randomly assigned 8-d l-amino acid diets that supplied either 12 and 28 or 20 and 36 mg lysine. At 1800 on day 8, a 24-h intravenous [13C]leucine tracer-infusion protocol was conducted to assess leucine oxidation and daily leucine balance at each lysine intake. Results: Mean 24-h leucine oxidation rates decreased significantly (P = 0.005) across different lysine intakes and were 104.1, 97.8, 87.3, and 87.3 mg•kg−1•d−1 at intakes of 12, 20, 28, and 36 mg•kg−1•d−1, respectively; mean 24-h leucine balances were 3.3, 9.1, 19.7, and 20.7 mg•kg−1•d−1, respectively (P = 0.015, mixed-model analysis of variance). Oxidation and balances differed significantly between the lower and higher lysine intakes but were not significantly different between the 12- and 20-mg and 28- and 36-mg test intakes. Two-phase regression analysis indicated a mean breakpoint at 29 mg lysine•kg−1•d−1 in the relation between lysine intake and leucine oxidation or balance. Conclusion: We propose a mean lysine requirement of 30 mg•kg−1•d−1 for healthy Indian adults, which is the same amount we proposed previously for Western populations.

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