Lysine requirement of healthy school-age children determined by the indicator amino acid oxidation method.
BACKGROUND
The current Dietary Reference Intake (DRI) recommendations for lysine requirements in children are based on a factorial estimate.


OBJECTIVE
The objective of the current study was to determine the lysine requirement in healthy school-age children by measuring the oxidation of l-[1-(13)C]phenylalanine to (13)CO(2) (F(13)CO(2)) in response to graded intakes of lysine.


METHODS
Five healthy school-age children randomly received each of 7 lysine intakes (5, 15, 25, 35 50, 65, and 80 mg x kg(-1) x d(-1)) along with an amino acid mixture to give a final calculated protein intake of 1.5 g x kg(-1) x d(-1) and an energy intake of 1.7 x resting energy expenditure (REE). The mean lysine requirement was determined by applying 2-phase linear regression crossover analysis on F(13)CO(2) data, which identified a breakpoint (requirement) at minimal F(13)CO(2) in response to graded lysine intakes.


RESULTS
The mean and population-safe (upper 95% CI) lysine requirements were determined to be 35 and 58 mg x kg(-1) x d(-1), respectively.


CONCLUSIONS
The mean and population-safe lysine requirements for children are similar to those for adults (36 and 52 mg x kg(-1) x d(-1), respectively), which suggests that the findings from the current study reflect predominantly the maintenance lysine requirements in children and not all requirements for growth. Therefore, to ensure age-appropriate growth in school-age children, we propose the addition of the requirement of lysine for growth (approximately 6 mg x kg(-1) x d(-1)) to the mean estimate. The new mean and population-safe lysine requirements are 41 and 58 mg x kg(-1) x d(-1), respectively; these values are significantly higher than the current DRIs of 37 and 46 mg x kg(-1) x d(-1), respectively.
Research Institute, The Hospital for Sick Children, Toronto, Canada.
Rajavel
R
Elango
Mohammad A
MA
Humayun
Ronald O
RO
Ball
Paul B
PB
Pencharz
D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D000601:Amino Acids, Essential; D001835:Body Weight; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D002648:Child; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007553:Isotope Labeling; D008239:Lysine; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction
D000596:Amino Acids; D000601:Amino Acids, Essential; D002247:Carbon Isotopes; D002245:Carbon Dioxide; D008239:Lysine