The intake of total protein, natural protein and protein substitute and growth of height and head circumference in Dutch infants with phenylketonuria.

In a previous study, Dutch children with phenylketonuria (PKU) were found to be slightly shorter than their healthy counterparts. In the literature, it has been hypothesized that a higher protein intake is necessary to optimize growth in PKU patients. The study aimed to investigate whether protein intake (total, natural and protein substitute) in this group might be an explanatory factor for the observed growth. Growth of height and head circumference and dietary data on protein intake (total, natural and protein substitute) from 174 Dutch PKU patients born between 1974 and 1996 were analysed retrospectively for the patients' first 3 years of life. Analyses were corrected for energy intake during the first year of life and for the clinical severity of the deficiency of phenylalanine hydroxylase by means of plasma phenylalanine concentration at birth. Neither protein nor energy intake correlated with height growth. A positive, statistically significant relation between head circumference growth and natural protein and total protein intake was found, but not with the intake of the protein substitute or energy. Therefore, this study suggests that improvement of the protein substitute rather than an increase of total protein intake may be important in optimizing head circumference growth in PKU patients.