Total sulfur amino acid requirement of healthy school-age children as determined by indicator amino acid oxidation technique.
BACKGROUND
Current total sulfur amino acid (TSAA) requirements of children are based on a factorial estimate that involves several assumptions.


OBJECTIVE
The objective was to determine the TSAA requirement (methionine alone) of healthy school-age children by measuring the appearance of 13CO2 (F13CO2) in breath after the oxidation of l-[1-13C]phenylalanine in response to graded methionine intakes.


METHODS
Six healthy school-age children randomly received each of 6 methionine intakes (0, 5, 10, 15, 25, and 35 mg.kg(-1).d(-1)) along with an amino acid mixture to give a final protein intake of 1.5 g.kg(-1).d(-1) and an energy intake of 1.7 x resting energy expenditure. The diet was devoid of cysteine. The mean TSAA requirement was determined by applying a biphase linear regression crossover analysis on F13CO2 data, which identified a breakpoint at minimal F13CO2 in response to graded methionine intakes.


RESULTS
The mean and population-safe (upper 95% CI) intakes of TSAA (as methionine) were determined to be 12.9 and 17.2 mg.kg(-1).d(-1), respectively.


CONCLUSIONS
The current study suggests that children of this age group have a mean TSAA requirement similar to that of adults (12.6 mg.kg(-1).d(-1)). Therefore, it is valid to use a factorial approach, which assumes that maintenance requirements in childhood are similar to adult requirements, to estimate TSAA requirements in school-age children.
Turner
Justine M
JM
Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
Humayun
Mohammad A
MA
Elango
Rajavel
R
Rafii
Mahroukh
M
Langos
Veronika
V
Ball
Ronald O
RO
Pencharz
Paul B
PB
D000603:Amino Acids, Sulfur / Q000008:administration & dosage / Q000378:metabolism; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D002648:Child; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008715:Methionine / Q000008:administration & dosage* / Q000378:metabolism*; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000032:analysis / Q000493:pharmacokinetics*
D000603:Amino Acids, Sulfur; D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D008715:Methionine