Early breastfeeding is linked to higher intelligence quotient scores in dietary treated phenylketonuric children.

Strict control of phenylalanine intake is the main dietary intervention for phenylketonuric children. Whether other dietary-related factors improve the clinical outcome for treated phenylketonuric children in neurodevelopmental terms, however, remains unexplored. We retrospectively compared the intelligence quotient (IQ) score of 26 school-age phenylketonuric children who were either breastfed or formula fed for 20-40 days prior to dietary intervention. Children who had been breastfed as infants scored significantly better (IQ advantage of 14.0 points, p = 0.01) than children who had been formula fed. A 12.9 point advantage persisted also after adjusting for social and maternal education status (p = 0.02). In this sample of early treated term infants with phenylketonuria there was no associated between IQ scores and the age at treatment onset and plasma phenylalanine levels during treatment. We conclude that breastfeeding in the prediagnostic stage may help treated infants and children with phenylketonuria to improve neurodevelopmental performance.