Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
Faculty of Kinesiology & Physical Education.
J Nutr. 2019 Feb 1;149(2):280-285. doi: 10.1093/jn/nxy250.
The requirement for dietary tryptophan in school-age children has never been empirically derived.
The objective of our study was to determine the tryptophan requirement of school-age children using the indicator amino acid oxidation technique.
Volunteer healthy school-age children, between 8 and 12 y, were enrolled and the oxidation of l-[13C]-phenylalanine to 13CO2 measured in response to graded intakes of dietary tryptophan. Seven children (3 boys, 4 girls) participated in the study and received randomly assigned tryptophan intakes ranging from 0.5 to 9.75 mg.kg-1.d-1 for a total of 36 studies. The diets provided energy at 1.5 times each subject's resting energy expenditure and were isocaloric. Protein was provided as an amino acid mixture on the basis of the egg protein pattern, and phenylalanine and tyrosine were maintained constant across the protein intake concentrations at 25 and 40 mg.kg-1.d-1. All subjects were adapted for 2 d before the study day to a protein intake of 1.5 g.kg-1.d-1. The mean tryptophan requirement was determined by applying a mixed-effect change-point regression analysis to F13CO2 (label tracer oxidation in 13CO2 breath) which identified a breakpoint in the F13CO2 in response to graded amounts of tryptophan.
The mean [estimated average requirement (EAR)] and upper 95% CI, (approximating the RDA) of tryptophan requirements were estimated to be 4.7 and 6.1 mg.kg-1.d-1, respectively.
Our results are similar to the current recommended EAR and RDA of 5 and 6 mg.kg-1.d-1 for healthy growing children based on the factorial calculation. Clinical Trials Registration No. NCT02018588.
学龄儿童的膳食色氨酸需求量从未通过实证研究得出。
本研究旨在采用指示氨基酸氧化技术确定学龄儿童的色氨酸需求量。
招募健康的学龄儿童志愿者，年龄 8 至 12 岁，测定其对不同剂量膳食色氨酸摄入的 l-[13C]-苯丙氨酸氧化为 13CO2 的情况。共有 7 名儿童（3 名男孩，4 名女孩）参与了这项研究，他们随机接受 0.5 至 9.75mg/kg/d 的色氨酸摄入量，共进行了 36 项研究。这些饮食提供的能量是根据每位受试者静息能量消耗的 1.5 倍，且热量摄入相等。蛋白质以基于鸡蛋蛋白模式的氨基酸混合物形式提供，在不同的蛋白质摄入量下，苯丙氨酸和酪氨酸的摄入量保持在 25 和 40mg/kg/d 不变。所有受试者在研究日之前，均经过 2 天的适应，使其蛋白质摄入量达到 1.5g/kg/d。采用混合效应拐点回归分析 F13CO2（13CO2 呼气中的标记示踪剂氧化），确定 F13CO2 对不同剂量色氨酸的响应转折点，从而确定平均色氨酸需求量。
色氨酸需求量的平均值（估计平均需求量（EAR））和上限 95%CI（接近 RDA）分别估计为 4.7 和 6.1mg/kg/d。
我们的结果与当前基于因子计算的健康生长儿童推荐的 5 和 6mg/kg/d 的 EAR 和 RDA 相似。临床试验注册号：NCT02018588。
