Daily methionine requirements of healthy Indian men, measured by a 24-h indicator amino acid oxidation and balance technique.
BACKGROUND
The 1985 FAO/WHO/UNU upper requirement for the sulfur-containing amino acids in healthy adults, which was set at 13 mg . kg(-)(1) . d(-)(1), is based on nitrogen balance studies in Western subjects. Short-term tracer-based studies also estimated a mean requirement of 13 mg . kg(-)(1) . d(-)(1), but whether this estimate is applicable to healthy populations worldwide is unknown.


OBJECTIVE
Using a 24-h indicator amino acid oxidation and balance method with 7 test methionine intakes (3, 6, 9, 13, 18, 21, and 24 mg . kg(-)(1) . d(-)(1)), we assessed methionine requirements in healthy, well-nourished Indians.


METHODS
Twenty-one healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods in which methionine intakes (diet devoid of cysteine) were equally placed on either side of the putative mean methionine requirement of 13 mg . kg(-)(1) . d(-)(1). Twenty-four-hour indicator amino acid oxidation and balance were measured on day 7 by using a 24-h [(13)C]leucine tracer infusion. The breakpoint in the relation between these values and the methionine intake was determined.


RESULTS
Two-phase linear regression of daily leucine oxidation against methionine intake estimated a breakpoint in the response curve at a methionine intake of 14 mg . kg(-)(1) . d(-)(1) (95% CI: 11, 23 mg . kg(-)(1) . d(-)(1)). The breakpoint estimated from the leucine balance-methionine intake relation was 15 mg . kg(-)(1) . d(-)(1) (95% CI: 11, 27 mg . kg(-1) . d(-1)).


CONCLUSIONS
From the 24-h indicator amino acid oxidation and balance approach, a mean methionine requirement, in the absence of cysteine intake, of 15 mg . kg(-1) . d(-1) is proposed for healthy, well-nourished Indian adults. This requirement is similar to that established in Western adults.
Kurpad
Anura V
AV
Department of Physiology and Division of Nutrition, St John's Medical College, Bangalore, India.
Regan
Meredith M
MM
Varalakshmi
Sureka
S
Vasudevan
Jahnavi
J
Gnanou
Justin
J
Raj
Tony
T
Young
Vernon R
VR
D000328:Adult; D002247:Carbon Isotopes; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007194:India; D007930:Leucine / Q000008:administration & dosage / Q000378:metabolism; D016014:Linear Models; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000378:metabolism*; D009751:Nutritional Requirements; D010084:Oxidation-Reduction
D002247:Carbon Isotopes; D008715:Methionine; D007930:Leucine