Market Research - Acceptability Study for a New PKU Protein Substitute

Inclusion Criteria: * Diagnosis of PKU or PKU variant requiring a protein substitute. * Subjects who were already taking a phenylalanine-free/low phenylalanine protein substitute and were willing to try the study product for 7 days. * Patients aged 3 years of age to adulthood. * Written informed consent obtained from participant or parental caregiver (as appropriate). Exclusion Criteria: * Presence of serious concurrent illness * Investigator's uncertainty about the willingness or ability of the patient to comply with the protocol requirements * Participation in any other studies involving investigational or marketed products concomitantly or within two weeks prior to entry into the study. * Any patients having taken antibiotics over the previous 2 weeks leading up to the study. * Patients less than 3 years of age.