Only the study team can determine whether someone qualifies for participation.
Inclusion criteria
i. A diagnosis of PKU on new-born screening requiring a low protein diet and Phe-free L-amino acid supplements.
ii. Aged between 6 months and 5 years.
iii. Already taking a second stage concentrated protein substitute as part of their PKU management OR is at the stage in their PKU management when a second stage concentrated protein substitute is recommended to commence.
iv. Willingly given, written, informed consent from parent/guardian.
v. Willingly given, written assent (if appropriate).
Exclusion criteria
i. Diagnosis of persistent hyperphenylalaninaemia, or mild PKU not requiring dietary treatment with a low protein diet and Phe-free L-amino acid supplements.
ii. Diagnosis of a concurrent condition which may adversely affect developmental progression and feeding ability.
iii. Participation in any other clinical trial/acceptability study.
iv. Any serious medical precluding the study intervention.
v. Use of additional macro/micronutrient supplements during the study period, unless clinically indicated and prescribed by the investigator (must be recorded in patient case record file).