title: Phenylalanine requirement in children with classical PKU determined by indicator amino acid oxidation.
abstract: Dietary restriction of phenylalanine is the main treatment for phenylketonuria (PKU), and current estimates of requirements are based on plasma phenylalanine concentration and growth. The present study aimed to determine more precisely the phenylalanine requirements in patients with the disease by use of indicator amino acid oxidation, with L-[1-13C]lysine as the indicator. Breath 13CO2 production (F 13 CO2) was used as the end point. Finger-prick blood samples were also collected for measurement of phenylalanine to relate phenylalanine intake to blood phenylalanine levels. The mean phenylalanine requirement, estimated using a two-phase linear regression crossover analysis, was 14 mg. kg(-1). day(-1), and the safe population intake (upper 95% confidence interval of the mean) was found to be 19.5 mg. kg(-1). day(-1). A balance between phenylalanine intake and the difference between fed and fasted blood phenylalanine concentration was observed at an intake of 20 mg. kg(-1). day(-1). The similarity between these two values (19.5 and 20 mg. kg(-1). day(-1)) suggests that the maximal phenylalanine intake for children with PKU should be no higher than 20 mg. kg(-1). day(-1).
authors.affiliation: Department of Nutritional Sciences, University of Toronto, Toronto M5S 3E2, Canada.
authors.forename: Glenda
authors.initials: G
authors.lastname: Courtney-Martin
authors.forename: Rachelle
authors.initials: R
authors.lastname: Bross
authors.forename: Mahroukh
authors.initials: M
authors.lastname: Raffi
authors.forename: Joe T R
authors.initials: JT
authors.lastname: Clarke
authors.forename: Ronald O
authors.initials: RO
authors.lastname: Ball
authors.forename: Paul B
authors.initials: PB
authors.lastname: Pencharz
mesh_terms: D000293:Adolescent; D001823:Body Composition; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism; D002247:Carbon Isotopes; D002648:Child; D005215:Fasting / Q000378:metabolism; D005260:Female; D005526:Food, Formulated / Q000592:standards*; D006128:Growth; D006801:Humans; D016014:Linear Models; D008239:Lysine / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D010661:Phenylketonurias / Q000178:diet therapy* / Q000378:metabolism*; D011659:Pulmonary Gas Exchange
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D008239:Lysine