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Nutrient intakes and physical growth of children with phenylketonuria undergoing nutrition therapy

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Abstract

Objective

To evaluate nutrient intakes, plasma phenylalanine (PHE) and tyrosine (TYR) concentrations, and physical growth of children with phenylketonuria undergoing nutrition management.

Design

Children were fed three different medical foods during a one-year study.

Subjects/setting

Children were evaluated at baseline and every three months in metabolic clinics. Children’s diets were managed at home.

Statistical analyses

Intakes of medical foods and nutrients, number of diaries with nutrients <67% and <100% of Recommended Dietary Intakes (RDI), and mean plasma PHE and TYR concentrations were compared among groups using two-way ANOVA. χ-squared test compared the percentage of plasma PHE and TYR concentrations in each group in specific categories. Height and body mass index were plotted against National Center for Health Statistics reference data; means were compared among groups. Tukey’s test compared groups with significant treatment effects.

Results

Mean intakes of nutrients, except energy by all groups and vitamin B-12 by the Periflex-fed group, met or exceeded RDIs. The oldest children tended to have the highest PHE intakes and plasma PHE concentrations. Mean length or height z score indicated normal linear growth. Mean body mass index z scores at study end suggested many children were overweight.

Applications

Dietitians should prescribe adequate medical food and encourage children with phenylketonuria to ingest all prescribed daily. Linear growth of children, where mean protein equivalent intakes ranged from 113% to 129% of RDI, was normal, demonstrating the need for a protein intake greater than RDIs when an elemental diet is the primary protein source. Dietitians should prescribe and carefully monitor energy intake, physical activity, and weight.

Section snippets

Ethical considerations

The investigators obtained approval of the study and consent form from the Institutional Review Board at the participating clinics or hospitals. Parents of all children signed informed consent forms.

Study design

A one-year study was conducted longitudinally in children with PKU (2.0 to 12.2 years of age) undergoing therapy with a medical food. Nutrient intake, physical growth, and plasma amino acid concentrations were assessed in 58 children. The study began in March 1996 and ended December 1999. Nine sites participated in the study.

Subject selection criteria

Children meeting the following criteria were eligible for study: diagnosed as having classical PKU and treatment initiated within the first month of life; free of major

Subjects

Twenty-seven Phenex-fed, 18 Periflex-fed, and 22 Phenyl-Free-fed children enrolled in the study. Data of 3 Phenex-fed, 4 Periflex-fed, and 2 Phenyl-Free-fed children are excluded from this report because of failure to attend clinic appointments (n=6), blood samples not obtained according to protocol (n=1), child consuming two different medical foods simultaneously (n=1), and one subject being placed on MVI. Mean±SEM ages of children at study entrance were Phenex-fed 5.0±0.5 years, Periflex-fed

Medical food and nutrient intakes

Phenex-fed children had a lower mean intake of medical food than the Periflex-fed and the Phenyl-Free-fed groups. This lower intake of medical food was related to the greater protein equivalent content of Phenex-2 (30 g/100 g) compared to that of Periflex and Phenyl-Free (20 g/100 g each). The younger age of the Phenex-fed group may also have been partially responsible for the differences in intake.

Mean energy intakes of the three groups of children, as a percentage of RDI, did not differ. Mean

Applications

Nutrient intakes of children with PKU met or exceeded RDIs when protocol-recommended protein intakes were ingested, suggesting that protein intakes were adequate when a major portion was obtained from an elemental medical food, indicating that dietitians should prescribe and encourage protein intakes greater than RDIs. Linear growth of children with PKU was within the normal range; however, obesity was present in a significant number of children, suggesting the need for dietitians to plot

Acknowledgements

The authors thank Mary Jane Kennedy, RN, and US Public Health Service grant No. M01-RR00039 for the General Clinical Research Center at Emory University School of Medicine, Atlanta, GA, for help with recruitment. This research was supported by Ross Products Division, Abbott Laboratories, Columbus, OH.

P. B. Acosta is Director, Metabolic Diseases, with Ross Products Division, Abbott Laboratories, Columbus, OH.

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    P. B. Acosta is Director, Metabolic Diseases, with Ross Products Division, Abbott Laboratories, Columbus, OH.

    S. Yannicelli is Director, Education, with Pharmavite, Northridge, CA. At the time the study was conducted, he was with Ross Products Division, Abbott Laboratories, Columbus, OH.

    R. Singh is Director, Nutrition, with the Division of Medical Genetics, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA.

    S. Mofidi is a metabolic dietitian with the Department of Pediatric Allergy, Mt Sinai Medical Center, New York, NY. At the time the study was conducted, she was with the Children’s Hospital of Los Angeles, Los Angeles, CA.

    R. Steiner is Chief of the Division of Metabolism, Departments of Pediatrics and Molecular and Medical Genetics, Oregon Health Sciences University, Portland, OR.

    E. DeVincentis is a metabolic dietitian with the Division of Genetics, Children’s Hospital, Buffalo, NY.

    E. Jurecki is a metabolic dietitian with the Regional Metabolic Center, Kaiser Permanente Medical Center, Oakland, CA.

    L. Bernstein is a metabolic dietitian with the Inherited Metabolic Disease Clinic, The Children’s Hospital, Denver, CO.

    S. Gleason is a metabolic dietitian with the Metabolic Center, University of Wisconsin, Madison.

    M. Chetty is a metabolic dietitian with Regional Metabolic Services, Kaiser Foundation Hospital, Los Angeles, CA.

    B. Rouse is Director, Child Development, with the Department of Pediatrics, University of Texas Medical Branch, Galveston.

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