Background: Earlier studies of the requirement for total sulfur amino acids (SAAs; methionine in the absence of cystine) in healthy, well-nourished Indians indicated a value of 15 mg.kg(-1).d(-1), but it is unknown whether this estimate is applicable to chronically undernourished subjects.
Objective: We assessed the total SAA requirement in otherwise clinically healthy, young, chronically undernourished adult Indians by using 7 test methionine intakes (3, 6, 9, 13, 18, 21, and 24 mg.kg(-1).d(-1)), without cystine, and by using both the 24-h indicator amino acid oxidation (24-h IAAO) and the 24-h indicator amino acid balance (24-h IAAB) methods.
Design: Twenty-one men were studied during each of 3 randomly assigned 7-d diet periods supplying methionine intakes (diet devoid of cystine) above and below the putative total 1985 FAO/WHO/UNU SAA requirement of 13 mg.kg(-1).d(-1). Twenty-four-hour IAAO and IAAB were measured on day 7 by use of a 24-h [(13)C]leucine tracer infusion. The breakpoint in the relation between these values and methionine intake was determined.
Results: Two-phase linear regression of daily leucine oxidation or the daily leucine balance against methionine intake estimated a breakpoint in the response curve at a methionine intake of 16 mg.kg(-1).d(-1) (95% Fiellers CI: 13, 22 mg.kg(-1).d(-1)).
Conclusions: On the basis of the 24-h IAAO-IAAB approach, a mean total SAA requirement of 16 mg.kg(-1).d(-1) is proposed for undernourished Indian adults. This is not significantly different from that determined in Western and Indian well-nourished adults.