Fifteen Years of Using a Second Stage Protein Substitute for Weaning in Phenylketonuria: a Retrospective Study

Background: In phenylketonuria (PKU), during weaning, it is necessary to introduce a second stage phenylalanine (Phe)-free protein substitute (PS) to help meet non-Phe protein requirements. Semi-solid weaning Phe-free PS have been available for >15 years, although no long-term studies have reported their efficacy.

Methods: Retrospective data from 31 children with PKU who commenced a weaning PS were collected from clinical records from age of weaning to 2 years, on: gender; birth order; weaning age; anthropometry; blood Phe levels; age commenced and dosage of weaning PS and Phe-free infant L-amino acid formula; natural protein intake; and issues with administration of PS or food.

Results: Median commencement age for weaning was 17 weeks (range 12-25 weeks) and, for weaning PS, 20 weeks (range 13-37 weeks). Median natural protein was 4 g day (range 3-11 g day ) and total protein intake was >2 g kg day from weaning to 2 years of age. Children started on 2-4 g day protein equivalent (5-10 g day of powder) from weaning PS, increasing by 0.2 g kg day (2 g day ) monthly to 12 months of age. Teething and illness adversely affected the administration of weaning PS and the acceptance of solid foods. Altogether, 32% of children had delayed introduction of more textured foods, associated with birth order (firstborn 80% versus 38%; P = 0.05) and food refusal when teething (80% versus 29%; P = 0.02).

Conclusions: Timing of introduction of solid foods and weaning PS, progression onto more textured foods and consistent feeding routines were important in aiding their acceptance. Any negative behaviour with weaning PS was mainly associated with food refusal, teething and illness. Parental approach influenced the acceptance of weaning PS.