Acceptability/Tolerance of Protein Substitutes in Tablet Form for the Dietary Management of Rare Aminoacidopathies

Inclusion Criteria: * Diagnosis of Tyrosinaemia type I, II III or Alkaptonuria requiring a tyrosine- and phenylalanine-free protein substitute. * Diagnosis of Homocystinuria requiring a methionine-free, cystine-enriched protein substitute. * Diagnosis of MSUD requiring a valine-, leucine- and isoleucine-free protein substitute. * Subjects who are already taking a protein substitute for one of the specified rare metabolic disorders and are willing to try the study product for 7 days. * Children aged 7 years and over. * Written informed consent obtained from parental caregiver. Exclusion Criteria: * Presence of serious concurrent illness * Lead Dietitian'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 children having taken antibiotics over the previous 2 weeks leading up to the study. * Children less than 7 years of age.