Effects of Dietary Fibre in Irritable Bowel Syndrome (IBS)

Currently, national and international guidelines are based upon trials of dietary fibre in IBS symptoms that report opposing effects. For this reason, recommendations regarding dietary fibre food supplementation in IBS are often conflicting. Indeed, the confusion surrounding dietary fibre recommendations in IBS is a consequence of the limited understanding of the different types of dietary fibres used, their physiology and their functions in different sub‐groups of IBS. Different fibres have different characteristics (e.g. solubility, viscosity and fermentability) which drive different functionalities (stool forming, fermentation) in the gastrointestinal tract, yet it is currently unknown whether administration of dietary fibre combinations will result in symptomatic improvement in people with IBS. Participants will be randomised to one of three parallel arms for a duration of 8 weeks. The study will consist of 4 visits in total. The first visit will involve taking consent and assessing eligibility. Participants will complete the Rome IV diagnostic criteria as part of their eligibility assessment. Participants will be asked to complete a food and symptom diary for the next 7 days. Diary data will be used to confirm frequency and severity of IBS symptoms and ensure there is no discrepancy between participant report on the Rome IV diagnostic criteria. Visit 2: Baseline (approx 1.5 hours). Height and weight will be recorded. Participants will complete 7 questionnaires, provide a stool sample, a blood sample and will ingest the SmartPill (wireless motility capsule). Participants will blinded to the intervention and will be provided with sachets containing either fibre 1 (combined fibres), fibre 2 (natural fibres) or placebo to consume over an 8‐week period. Visit 3: Mid‐point (approx 1 hour). Participants will complete 5 questionnaires and provide a stool sample. Visit 4: Endpoint (approx 1.5 hours). Height and weight will be recorded. Participants will complete 7 questionnaires, provide a stool sample, a blood sample and will ingest the SmartPill (wireless motility capsule).