Methionine kinetics and balance at the 1985 FAO/WHO/UNU intake requirement in adult men studied with L-[2H3-methyl-1-13C]methionine as a tracer.
The upper range of the requirement for methionine plus cystine in healthy adults was proposed in 1985 by FAO/WHO/UNU to be 13 mg.kg body wt-1.d-1. To explore the validity of this estimate, five healthy, young adult men were given for 7 d a diet based on an L-amino acid mixture supplying 13 mg methionine.kg-1.d-1 (87 mumol.kg-1.d-1) without cystine. Constant intravenous infusions of L-[2H3-methyl-1-13C]methionine were given on days 5 and 7 while subjects were in the fed and postabsorptive states, respectively. Estimates were made of methionine oxidation, and daily methionine balance was derived from the intake-oxidation data. For the five subjects, methionine balances were -0.9, +0.7, +3.5, -3.1, and -3.8 mg kg-1.d-1, or -6, +5, +23, -21, and -26 mumol.kg-1.d-1. These findings lead to the conclusion that the upper range of the requirement for methionine plus cystine probably exceeds 13 mg.kg-1.d-1 in healthy young adults. The implications of this conclusion for establishing an appropriate amount of sulfur amino acids in an amino acid requirement pattern for adults is discussed.
Young
V R
VR
Shriners Burns Institute, Boston, MA.
Wagner
D A
DA
Burini
R
R
Storch
K J
KJ
D000328:Adult; D002247:Carbon Isotopes; D003903:Deuterium; D006801:Humans; D007262:Infusions, Intravenous; D007700:Kinetics; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism*; D009751:Nutritional Requirements
D002247:Carbon Isotopes; D008715:Methionine; D003903:Deuterium; C038344:methionine methyl ester