Market Research - Acceptability Trial for a New PKU Amino Acid Based Protein Substitute

Inclusion Criteria: * Diagnosis of PKU or PKU variant requiring a phenylalanine-free protein substitute * Subjects who are already taking a phenylalanine-free protein substitute and are willing to try the study product for 7 days * Patients aged 3 years of age to adulthood * Written informed consent obtained from parental caregiver 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.