 The development of preventative nutritional strategies to promote healthy ageing is becoming increasingly important. Elevated thresholds for taste and smell, coupled with swallowing difficulties and masticatory dysfunction, often result in nutritionally imbalanced diets among the elderly. This can induce great changes in the composition and metabolic activities of the gut microbiome, leading to decreased intestinal motility and impaired bowel function. This can result in constipation or diarrhoea, increased basal levels of inflammation, immunosenescence and morbidity. The objectives of this study are to use dietary modification to improve gut health in older people. Diets high in resistant starch or dietary fibre will be given to 50 elderly volunteers 70-95 years living in the community, in a randomised double-blind cross-over study. The aim is to investigate the effects on microbiome composition and functionality through fermentation, reduced putrefaction, and modification of blood markers associated with obesity and diabetes. 