Aromatic amino acid requirements in healthy men measured by indicator amino acid oxidation

In the current literature, no agreement exists on estimates for aromatic amino acid (phenylalanine plus tyrosine) requirements as measured by stable-isotope techniques. The goal of the present study was to determine the phenylalanine requirement in healthy men who were fed a diet without tyrosine by...

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Bibliographic Details
Published in:The American journal of clinical nutrition 2006, Vol.83 (1), p.82-88
Main Authors: HSU, Jean W.-C, GOONEWARDENE, Laksiri A, RAFII, Mahroukh, BALL, Ronald O, PENCHARZ, Paul B
Format: Article
Language:English
Subjects:
Adult
Amino acids
Amino Acids, Aromatic - administration & dosage
Amino Acids, Aromatic - metabolism
Biological and medical sciences
Breath Tests
Canada
Carbon Dioxide - analysis
Carbon Isotopes
Cross-Over Studies
Dose-Response Relationship, Drug
Feeding. Feeding behavior
Fundamental and applied biological sciences. Psychology
Humans
Linear Models
Lysine - metabolism
Male
Men
Nutrition Policy
Nutritional Requirements
Oxidation
Oxidation-Reduction
Phenylalanine - administration & dosage
Phenylalanine - metabolism
Tyrosine - administration & dosage
Tyrosine - metabolism
Vertebrates: anatomy and physiology, studies on body, several organs or systems
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Summary:In the current literature, no agreement exists on estimates for aromatic amino acid (phenylalanine plus tyrosine) requirements as measured by stable-isotope techniques. The goal of the present study was to determine the phenylalanine requirement in healthy men who were fed a diet without tyrosine by using the indicator amino acid oxidation method. Five healthy men were assigned to receive in random order diets devoid of tyrosine and with 8 graded intakes of phenylalanine (5, 10, 15, 25, 35, 45, 60, and 70 mg x kg(-1) x d(-1)). The phenylalanine requirement was measured by the rate of 13CO2 release (F13CO2) from L-[1-(13)C]lysine oxidation. The graded intakes of phenylalanine had no effect on lysine flux, as required for this method. The phenylalanine (ie, total aromatic amino acid) requirement, in the absence of tyrosine, was estimated to be 48 mg x kg(-1) x d(-1) by applying a two-phase linear regression crossover model to the F13CO2 data. In the absence of tyrosine, the mean phenylalanine requirement is higher than the current FAO/WHO/UNU (1985) and Dietary Reference Intake (2002) recommendations.
ISSN:0002-9165
1938-3207
DOI:10.1093/ajcn/83.1.82