FODMAP Restriction and IBS Symptom Reduction: A Multicentre RCT

Irritable bowel syndrome (IBS) affects up to 15% of the global population, yet dietary treatment has historically been empirical and inconsistent. This double-blind randomised controlled trial enrolled 412 adults with Rome IV-confirmed IBS (IBS-D, IBS-C, and IBS-M subtypes) across 9 academic gastroenterology centres. Participants were randomised to three dietary conditions for 6 weeks: strict low-FODMAP restriction, a high-fibre diet, or a sham dietary protocol designed to control for non-specific effects of dietary attention.

The primary outcome — IBS Symptom Severity Score (IBS-SSS) — was assessed at 2, 4, and 6 weeks by blinded investigators. Low-FODMAP adherents demonstrated a 76% composite symptom reduction at week 6, significantly exceeding the high-fibre arm (41%) and sham arm (28%), both p<0.001. Symptom improvement was detectable as early as week 2 in 68% of FODMAP-adherent participants. The protocol was particularly effective in IBS-D and IBS-M subtypes. These results establish the low-FODMAP protocol as the evidence-based first-line dietary intervention for the majority of IBS presentations, superseding generic high-fibre and sham approaches.