This is a market research, observational study to evaluate the tolerability and acceptability of an MCT based formula for infants and young people with long chain fatty acid oxidation disorder from birth to 18 months. Patients with a confirmed diagnosis of a fatty acid oxidation disorder, which requires a specialist diet including MCT will be included in this study

Inclusion Criteria:

• Diagnosis of a fatty acid oxidation disorder requiring a ketogenic or a specialist diet as part of their treatment, which includes MCT.
• Patients from birth to 18 months
• Written informed consent obtained from patient or 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 over 18 months of age

This study will be used to demonstrate acceptability for registration and reimbursement of these foods for special medical purposes.