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


University Hospital, Rouen




Irritable Bowel Syndrome


Dietary Supplement: Low FODMAP diet

Study type


Funder types




Details and patient eligibility


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.


50 estimated patients




18 to 80 years old


No Healthy Volunteers

Inclusion criteria

  • IBS according to Rome IV criteria
  • Normal blood test (cell blood count, C Reactive Protein, thyroid-stimulating hormone, anti transglutaminase antibodies) in the last 12 months
  • IBS severity score (IBS-SSS) >175/500
  • IBS treatments stable in the last month
  • Effective contraception since 1 month for women in childbearing age

Exclusion criteria

  • Anorexia nervosa or any eating disorders deemed incompatible
  • Organic gastroenterological diseases (inflammatory bowel disorder, microscopic colitis, gastrointestinal cancer, celiac disease)
  • Contra-indication to the wireless motility capsule (intestinal stenosis, digestive fistula or obstruction, history of bezoar, gastrointestinal surgery in the last 3 months, acute diverticulitis, cardiac pacemaker, implanted electromedical device, magnetic resonance imaging planned in the 5 days after the wireless motility capsule, swallowing disorder)
  • Breastfeeding or pregnant women
  • Participation in another clinical trial in the last 2 weeks
  • Patient who could not stop proton pump inhibitor treatment for 10 days
  • Person with administrative or judicial decision or under legal protection measure

Trial design

Primary purpose




Interventional model

Single Group Assignment


None (Open label)

50 participants in 1 patient group

IBS patients
Experimental group
Patients suffering from IBS according to Rome IV criteria
Dietary Supplement: Low FODMAP diet

Trial contacts and locations



Central trial contact

Chloé Melchior, MD, PhD; Florian Vallin

Data sourced from clinicaltrials.gov

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