Recommendations for protein and energy intakes by patients with phenylketonuria

Recent reports describe poor growth in treated children with phenylketonuria (PKU). That poor growth is not a concomitant of the disorder and need not result from therapy is demonstrated by data from the U.S.A. PKU Collaborative Study and from recent data from the U.S.A. In these studies, sufficient protein equivalent was supplied by medical food containing either a low phenylalanine (Phe) casein hydrolysate or Phe-free L-amino acids. Protein and energy intakes of infants and children with PKU who grew well are compared to intakes of normal North American children. Factors that influence nitrogen (N) requirements include: state of health, energy intake, the form in which N is administered and the size of the dose. Failure to prevent poor growth in childhood may lead to a stunted adult [13] who is at risk for obesity. The use of actual body weight as a basis for calculating protein and energy requirements is appropriate only when the child is growing normally. Based on experience with PKU in the U.S.A., the following are recommended: (1) a protocol that prescribes a range for Phe, protein, and energy for infants and children should be developed; (2) adequate protein equivalent to cover N losses due to poor utilization of amino acids and protein hydrolysates should be prescribed; (3) medical food should be administered in several doses throughout the day; (4) a source of Phe should be fed with the medical food; (5) adequate energy should be prescribed to prevent excess use of amino acid for energy purposes; (6) nutrition support during illness should be appropriate to help prevent muscle protein catabolism with attendant elevated plasma Phe.