Feeding Models in Classical Phenylketonuria: Do They Make a Difference in Infant Sleep?

Background: Phenylketonuria (PKU) is an inherited metabolic disorder that requires early diagnosis and strict phenylalanine (Phe)-restricted diet to prevent neurocognitive impairment. Various infant feeding models have been used to achieve optimal metabolic control during early life. The aim of this study was to compare two different feeding models for infants with classical PKU in terms of metabolic control, growth parameters, micronutrient status, the process of introducing complementary foods, and with a particular focus on sleep quality.

Methods: In this prospective observational study, 26 infants with classical PKU were followed for 12 months. Patients were assigned to one of two feeding groups: Group-1 received breast milk and Phe-free formula in alternating feeds, while Group-2 received Phe-free formula followed by breastfeeding until satiety. Blood Phe, micronutrient levels and anthropometric measurements were recorded. Sleep quality was evaluated using the Brief Infant Sleep Questionnaire-Revised (BISQ-R). A structured set of parental questions was used to evaluate their experiences during the complementary feeding period.

Results: No statistically significant differences were observed between the groups in terms of blood Phe levels, anthropometric measurements, serum levels of iron, ferritin, vitamin-B12, vitamin-D, and zinc. Complementary feeding tolerance were similar across the groups. The BISQ-R analysis revealed no significant differences between the groups.

Conclusions: Both feeding models were equally effective in maintaining metabolic control, supporting normal growth, complementary feeding processes, and preserving sleep quality during infancy. These findings suggest that either approach can be adopted based on the preference of the caregiver and the practicality of the clinical setting.