Low Residue Diet Study in Mitochondrial Disease

All patients will be provided with a LRD plan (\< 10g fibre per day) for 12 weeks between visits 2 and 3. They will also be supplemented with multivitamin and mineral tablet or liquid (Forceval) to meet nutrient requirements (prescribed as standard care). The dietitian will provide written and oral information about the LRD and weekly telephone calls to assess patient's progress on the diet.