Zinc status and growth of children undergoing treatment for phenylketonuria

Abstract

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.

The effect of treatment on zinc, copper and calcium status in children with phenylketonuria

“…The mean daily zinc intake in their subjects was higher (112 lamol day-l), in keeping with the recommended daily allowances of the Food Nutrition Board (1980). The significantly lower hair zinc concentrations in PKU children in the Alder Hey study (daily minimum zinc intake = 59 lamol day-1), compared with controls, supports Acosta's (1982) findings. The discrepancy between the two former studies may be explained by Lawson's patients displaying increased zinc uptake following their recent introduction to the new high zinc formula (8-28 days), having been previously maintained in a zinc-deficient state on a low zinc content formulation, or reflect differing methods of assaying sufficiency of the element.…”

“…The discrepancy between the two former studies may be explained by Lawson's patients displaying increased zinc uptake following their recent introduction to the new high zinc formula (8-28 days), having been previously maintained in a zinc-deficient state on a low zinc content formulation, or reflect differing methods of assaying sufficiency of the element. Acosta's (1982) low values were not explicable on the basis of a low total dietary intake since the PKU groups daily average intake was, in fact, higher than the calculated intake for normal young children they had previously examined. It was, therefore, concluded that the bioavailability of the zinc fi'om these children on a low phenylatanine diet was poor.…”

Biochemical and neuropsychological effects of elevated plasma phenylalanine in patients with treated phenylketonuria. A model for the study of phenylalanine and brain function in man.

“…Patients equilibrated for 7 d after each change in dietary phenylalanine. Past plasma concentrations of phenylalanine on known intake and genotyping of parents were used to determine the amount of phenylalanine added to patient formulation for restriction and loading (23,24). Patients whose entering concentration of plasma phenylalanine was high either because of poor control or because of diet discontinuation for several years were on the highlow-high protocol.…”

Problems related to diet management of maternal phenylketonuria

“…Elemental diets may result in normal growth (Holm et al, 1979) and development (Dobson et al, 1977) whilst creating a host of problems (Hanley et al, 1970;Acosta et al, 1982;Endres et al, 1984). Elemental diets predispose to management problems and nutrient deficiencies and excesses in vulnerable patients for at least 6 reasons:…”

“…acceptance or availability of more appropriately formulated diets. Use of products by age-specific populations for which they were not intended often precipitates nutrient deficiencies (Acosta et al, 1982) and dietary excesses (Acosta et al, 1977).…”