Zinc status and growth of children undergoing treatment for phenylketonuria

Children with phenylketonuria (PKU) are treated with semi-synthetic diets restricted in phenylalanine. Low-phenylalanine or phenylalanine-free formulae provide the majority of protein and energy in the diet while phenylalanine requirements are met by low-protein natural foods. Because of the restriction of natural protein sources in this diet, the study assessed the zinc nutrition of 22 treated children with PKU (aged from 1 month to 8 1/2 years) and correlated linear growth with zinc status. The mean (+/- SE) plasma zinc concentration of the PKU population was 66.6 +/- 3.3 micrograms/dl. The mean (+/- SE) hair zinc concentration was 70.2 +/- 11.5 micrograms/g. The mean plasma and hair zinc concentrations of the PKU population were significantly different (p less than 0.05) when compared with mean (+/- SE) normal values of 84.2 +/- 2.9 micrograms/dl and 130.7 +/- 8.3 micrograms/g, respectively. The mean (+/- SD) dietary zinc intake of 10 PKU patients was 8.56 +/- 2.68 mg/day. No significant differences (p less than 0.123) were found when the mean zinc intake was compared with National Academy of Sciences Recommended Dietary Allowance for age of 10 mg/day. No significant correlations were found when plasma and hair zinc concentrations were plotted with height percentiles. Further studies are required to assess the effects of zinc supplementation and the bioavailability of zinc from low-phenylalanine diets.