Efficacy of a Low FODMAP Diet According to Colonic pH in Irritable Bowel Syndrome Patients

Treatments efficacy in irritable bowel syndrome (IBS) patients is inconstant and predictive factors of their efficacy are needed. The role of dysbiosis in IBS is well-known. Another way to identify microbiota differences is to assess its metabolic activity. It has been demonstrated that colonic pH in IBS patients is lower than in healthy volunteers, reflecting a highest colonic fermentation. Colonic acidification is able to sensitize colonic mechano-receptors to distension. Microbiota profile is able to predict the response to a low Fermentable Oligo, Di, Monosaccharides And Polyols (FODMAPs) diet, but is not available in clinical routine.

The aim of our study is to assess the link between colonic fermentation (measured by colonic pH) and the efficacy of a low FODMAPs diet in IBS patients (measured by IBS severity scoring system (IBS-SSS)). We hypothesis that IBS patients with a lower colonic pH will have a better efficacy of the low FODMAPs diet. It might allow in the future personalized medicine.

50 IBS patients according to Rome IV criteria will be included in our study. All patients will have a measure of their colonic pH by wireless motility capsule. Patients will follow a low FODMAPs diet for 6 weeks after an education by a trained dietician. All participants will fill validated questionnaires before and after 6 weeks of low FODMAPs diet: IBS-SSS, Gastro Intestinal Quality of Life Index (GIQLI), Hospital Anxiety and Depression (HAD) scale. Microbiota, metabolomic and short chain fatty acid will be analysed before and after the intervention. The number of patients was calculated to assess the correlation between colonic pH and the variation of IBS-SSS before and after the intervention.