Nutrient Intake and Growth of Infants with Phenylketonuria Undergoing Therapy

Abstract

Background:Because of reports of poor growth, a study was conducted for 6 months in 35 infants with classic phenylketonuria diagnosed during the neonatal period who were fed Phenex‐1 Amino Acid Modified Medical Food With Iron (Ross Products Division, Columbus, OH, U.S.A.) as their primary protein source.Methods:Diet diaries and anthropometric measures were obtained monthly as part of a larger study in which nutrition status was evaluated.Results:In 6‐month‐old infants, mean percentiles for crownheel length (59.14± 4.31 SEM), head circumference (63.88 ± 4.50) and weight(71.51 ± 4.25) were normal. Mean (± SEM) daily intake of medical food was 79 ± 4 g; protein and energy intakes were 17.3± 0.6 g and 2772 ± 75.6 kJ (660 ± 18 kcal). Mean daily phenylalanine and tyrosine intakes per kilogram of body weight were 40± 1 mg and 219 ± 9 mg. Intakes of protein, energy, and tyrosine were positively correlated with crown‐heel length, head circumference, and weight at 3 months of study. Overall plasma phenylalanine and tyrosine concentrations during the 6‐month study were 297 ± 41 µmol/l and 58 ± 5 µmol/l, respectively. Neither plasma phenylalanine nor tyrosine concentration was correlated with growth.Conclusion:Phenex‐1 supports normal growth when fed in adequate amounts. These data support those of the Medical Research Council Working Party on Phenylketonuria for 3 g/kg per day of amino acids from medical food.