Lazaris-Brunner G, Rafii M, Ball R O, Pencharz P B
Department of Nutritional Sciences, University of Toronto, Ontario, Canada.
Am J Clin Nutr. 1998 Aug;68(2):303-10. doi: 10.1093/ajcn/68.2.303.
To determine tryptophan requirements with use of the indicator amino acid oxidation technique, we studied 5 healthy, premenopausal women who each consumed 6 different intakes of tryptophan. The energy-sufficient diet contained 1.0 g x kg(-1) x d(-1) of an L-amino acid mixture patterned after egg protein, with adequate phenylalanine (14 mg x kg(-1) x d(-1)) and excess tyrosine (40 mg x kg(-1) x d(-1)). The effect of graded alterations in dietary tryptophan on phenylalanine flux and oxidation was studied by using L-[1-(13)C]phenylalanine as the indicator amino acid. Graded increases in tryptophan had no effect on phenylalanine flux. Determined by two-phase linear regression crossover analysis, the mean tryptophan requirement based on indicator (phenylalanine) oxidation was 4.01 mg x kg(-1) x d(-1), with a safe intake at 5.02 mg x kg(-1) x d(-1). These results show that the indicator amino acid oxidation technique can be used to determine the requirement for amino acids such as tryptophan that cannot be successfully studied by direct oxidation because of their characteristic metabolism. Our value of safe intake for 95% of the population was found to be 43% higher than that reported previously for adults.
为了使用指示氨基酸氧化技术来确定色氨酸需求量，我们研究了5名健康的绝经前女性，她们每人摄入6种不同量的色氨酸。能量充足的饮食包含按鸡蛋蛋白模式配制的1.0 g·kg⁻¹·d⁻¹的L-氨基酸混合物，其中苯丙氨酸充足（14 mg·kg⁻¹·d⁻¹），酪氨酸过量（40 mg·kg⁻¹·d⁻¹）。通过使用L-[1-(¹³)C]苯丙氨酸作为指示氨基酸，研究了膳食色氨酸分级改变对苯丙氨酸通量和氧化的影响。色氨酸的分级增加对苯丙氨酸通量没有影响。通过两阶段线性回归交叉分析确定，基于指示（苯丙氨酸）氧化的平均色氨酸需求量为4.01 mg·kg⁻¹·d⁻¹，安全摄入量为5.02 mg·kg⁻¹·d⁻¹。这些结果表明，指示氨基酸氧化技术可用于确定因代谢特性而无法通过直接氧化成功研究的氨基酸（如色氨酸）的需求量。我们发现95%人群的安全摄入量值比先前报道的成年人值高43%。
