Evaluating the Efficacy of PKU Synergy in Patients Expressing Phenylketonuria or Hyperphenylalaninemia

Inclusion Criteria: * Male or female * Over 16 years of age * Diagnosed with proven PKU or hyperphenylalaninemia with an increased phenylalanine-tolerance/intake * Currently taking a maximum of 1 protein substitute per day (equal to 20g protein equivalent) * Have a minimum blood phenylalanine level of ≥ 600 umol/L (for PKU patients) * Have relaxed (if not stopped) their dietary and protein substitute regimen for at least 1 month prior to trial commencement * Have Written informed consent from patient Exclusion Criteria: * Pregnant or lactating * Requiring nutritional support (including enteral and parenteral nutrition) * Major hepatic or renal dysfunction * Participation in other studies within 1 month prior to entry of this study * Allergy to any of the study product ingredients, including milk protein or soya * Investigator concern around willingness/ability of patient to comply with protocol requirements