Threonine kinetics at graded threonine intakes in young men.
A study was undertaken in eight healthy young men to examine the effects of varying intakes of threonine on plasma free threonine concentrations and threonine kinetics, using a 3 h constant intravenous infusion of L-[1-13C]threonine. Subjects consumed diets based on an L-amino acid mixture, in which the quality of threonine was reduced every 7 days. On the last day of each diet period, determinations of plasma threonine flux and threonine oxidation were carried out while subjects consumed small meals, each supplying 1/12 daily intake, at hourly intervals. Threonine oxidation rates fell with reduced threonine intake, reaching a relatively constant level at intakes of 20 mg.kg-1.day-1 and below. These metabolic data are discussed in relation to the currently established value of 7 mg.kg-1.day-1 as the upper range of the threonine requirement for healthy young adults. It is concluded that actual threonine requirements may be considerably higher for this age group.
D000293:Adolescent; D000328:Adult; D004032:Diet; D005998:Glycine / Q000097:blood; D006801:Humans; D007263:Infusions, Parenteral; D007700:Kinetics; D008297:Male; D013912:Threonine / Q000008:administration & dosage / Q000097:blood*
D013912:Threonine; D005998:Glycine