Effects of a Personalised FODMAP Diet Versus the National Institute for Health and Care Excellence ( NICE ) Dietary Advice on Symptom Control in Patients With Irritable Bowel Syndrome: Randomised Clinical Trial

INTRODUCTION: Irritable bowel syndrome is a disorder of the gut-brain interaction characterised by chronic abdominal pain and altered bowel habits, with substantial impact on quality of life. Symptoms are associated with foods trigger, leading to specific dietary interventions. Adherence and acceptability may improve when dietary interventions are personalised and less restrictive. While the low-FODMAP diet is effective, its restrictiveness may limit long-term adherence. Personalised dietary strategies may offer comparable benefit with greater feasibility. METHODS: In this parallel-group, randomised clinical trial, adults fulfilling Rome III criteria for IBS were assigned (1:1) to NICE dietary advice or an personalised FODMAP diet for four weeks. The personalised diet involved selective 50% reduction of patient-specific high-FODMAP foods identified through structured food and symptom diaries. Symptoms were evaluated using a 4-point Likert scale, with adequate relief defined as ≥ 1-point improvement in both abdominal pain and bowel habits. Dietary intake, quality of life (SF-36) and anthropometric measures were recorded at baseline and follow-up. RESULTS: Sixty-nine participants were enrolled (85% women; mean age 39.9 ± 12.2 years). Baseline demographics, anthropometric variables and IBS subtypes were similar across groups. Both interventions significantly reduced caloric intake and improved symptom severity, particularly abdominal pain, distension, constipation and diarrhoea. Adequate relief occurred in 41.2% of the NICE group and 54.5% of the personalised FODMAP group (p = 0.33). No significant between-group differences were observed. CONCLUSIONS: An individualised, less restrictive personalised FODMAP diet yields symptom improvement comparable to NICE dietary advice while preserving nutritional adequacy. Personalised dietary strategies may enhance feasibility and long-term adherence in IBS management.