Review article: the impact of diet on ileo-anal pouch function and on the pathogenesis of pouchitis

Background There is expanding interest in the role that diet plays in ileoanal pouch function and in the pathogenesis of pouchitis. Aims To present a narrative review of published literature regarding the relationship of diet with pouch function and the pathogenesis of pouchitis, and to provide potentially beneficial dietary strategies. Methods Current relevant literature was summarised and critically examined. Results Dietary components influence pouch function via their effect on upper gastrointestinal transit, small bowel water content and the structure and fermentative activity of the pouch microbiota. FODMAPs in fruits and vegetables appear to affect pouch function the most, with intake positively associated with increased stool frequency and reduced consistency. Dietary factors that influence the pathogenesis of pouchitis appear different and, at times, opposite to those better for optimising function. For example, risk of pouchitis appears to be inversely associated with intake of fruits. The food components mechanistically responsible for this observation are not known, but a rich supply of fermentable fibres and micronutrients in such foods might play a beneficial role via modulation of microbial community structure (such as increasing diversity and/or changing microbial communities to favour 'protective' over 'pathogenic' bacteria) and function and/or anti-inflammatory effects. Conclusion Available data are weak but suggest tailoring dietary recommendations according to pouch phenotype/behaviour and pouchitis risk might improve outcomes. More sophisticated dietary strategies that utilise the physiological and pathophysiological effects of dietary components on ileoanal pouches have potential to further improve outcomes. Welldesigned, adequately powered studies are required.