Protein substitute dosage in PKU: how much do young patients need?

Area of Science:

• Biochemistry
• Pediatric Nutrition
• Metabolic Disorders

Background:

• Optimal protein substitute dosage remains undetermined for children with phenylketonuria (PKU).
• Current UK Medical Research Council (MRC) recommendations guide protein substitute dosing.

Purpose of the Study:

• To compare the efficacy of a lower protein substitute dose against the standard UK MRC-recommended dose in managing blood phenylalanine levels in children with PKU.

Main Methods:

• A six-week randomized crossover study involving 25 children (aged 2-10 years) with well-controlled PKU.
• Two protein substitute doses were administered: 2 g/kg/day (Protocol A) and 1.2 g/kg/day (Protocol B) for 14 days each, with a 14-day washout period.
• Plasma phenylalanine levels were monitored twice daily during the final week of each protocol.

Main Results:

• The lower protein substitute dose (1.2 g/kg/day) resulted in a significant increase in median plasma phenylalanine levels (301-337 mumol/l).
• The higher protein substitute dose (2 g/kg/day) maintained phenylalanine levels comparable to baseline/control values.
• Significant inter-individual variability in response to protein substitute dosage was observed.

Conclusions:

• Higher protein substitute dosages appear more effective in reducing blood phenylalanine concentrations in children with PKU.
• The impact of protein substitute dosage on phenylalanine control is variable and individualized.
• Carbohydrate and fat content of the protein substitute may influence its efficacy.