Randomised controlled trial: effects of gluten‐free diet on symptoms and the gut microenvironment in irritable bowel syndrome

BACKGROUND: A gluten‐free diet reduces symptoms in some patients with irritable bowel syndrome (IBS) through unclear mechanisms. AIMS: To assess the effects of gluten‐free versus gluten‐containing diet on symptoms and the gut microenvironment, and to identify predictors of response to the gluten‐free diet in IBS METHODS: Twenty patients with IBS and 18 healthy controls (HC) followed a gluten‐free diet during two 14‐day intervention periods where they sprinkled either gluten (14 g/day) or rice flour powder over their meals. Primary outcomes included effects of the interventions on IBS symptoms (IBS‐SSS) and bowel habits. Secondary outcomes included effects of gluten‐free diet on faecal microbiota and metabolite profile. RESULTS: IBS symptoms improved during the gluten‐free (p = 0.02), but not the gluten‐containing period, with no difference between the interventions. IBS patients reported fewer loose stools during the gluten‐free intervention (p = 0.01). Patients with IBS and HC presented distinct metabolite profiles based on the effects of the gluten‐free diet (p < 0.001). True responders (reduced IBS‐SSS by ≥50 solely after gluten‐free period) and non‐responders were discriminated based on the effects of the gluten‐free diet on the microbiota (p < 0.01) and metabolite profiles (p < 0.001). The response to the gluten‐free diet could be predicted by the metabolite profile before the intervention (p < 0.001). CONCLUSIONS: A gluten‐free diet may influence symptoms in a subset of patients with IBS, with a particular effect on bowel habits. A gluten‐free diet seems to impact the gut microenvironment. Responsiveness to the gluten‐free diet may be predicted by the metabolite profile. Clinicaltrials.gov: NCT03869359.