Nutrition studies in treated infants and children with phenylketonuria: vitamins, minerals, trace elements

Chemically defined or elemental medical foods provide the majority of protein equivalent in the diets of children treated for phenylketonuria (PKU). Because of the restricted intake of high biologic value protein, children with PKU often have lower than normal plasma concentrations of ferritin and zinc. Few reported studies are available on vitamin status of children with PKU undergoing treatment. This report addresses intakes of iron, zinc and vitamin A and their plasma concentrations in children ingesting either a low phenyl-alanine (Phe) casein hydrolysate or a Phe-free L-amino acid mix. With significantly greater than recommended mean intakes of iron and low to recommended mean intakes of zinc, individual plasma ferritin concentrations were often in the deficient (< 12 ng/ml) or marginal (12 < 20 ng/ml) range; plasma zinc concentrations were usually normal when patients received an L-amino acid mix. When L-amino acids were the source of protein equivalent for infants, 48% of plasma retinol concentrations were in the marginal (20 < 30 micrograms/dl) or deficient range (< 20 micrograms/dl) in spite of most vitamin A intakes being greater than Recommended Dietary Allowance for age. Some hypothetical reasons for low concentrations of plasma ferritin and retinol are discussed.