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

Intervention: range of protein substitute tablets. Subjects who currently take a protein substitute for the dietary management of either tyrosinaemias or alkaptonuria, homocystinuria, or MSUD will be recruited. Subjects will take the study product for 7 days. Daily questionnaires will be completed (ease of preparation,administration; any problems or gastrointestinal effects). Subjects will replace some or their entire usual protein substitute with the new product suitable for their diagnosed rare metabolic disease. The amount of tablets prescribed will be calculated to provide the same amount of protein as their usual protein substitute. Additional questions at the beginning and end of the study will record information on organoleptic properties, presentation and packaging of the product. Routine weekly blood samples will be collected and analysed for amino acids typically for the metabolic control of the individual specified metabolic disorders as is usual clinical practice.