The Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols Diet Is Effective in Irritable Bowel Syndrome With Constipation: A Single Center Tertiary Care Clinical Practice Evaluation

Background/Aims: The low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet is a well-researched treatment for diarrhea-predominant irritable bowel syndrome (IBS-D), but its value for constipation-predominant IBS (IBS-C) is uncertain.Clinicians may hesitate to recommend it for IBS-C, fearing it could worsen constipation or offer little relief.This study aims to assess the diet's effectiveness across all IBS subtypes, specifically investigating its impact on stool patterns in IBS-C and the correlation with symptom relief.Methods: This prospective service evaluation involved 294 IBS patients (84% female, mean age 44.6) attending dietitian-led group sessions on FODMAP restriction (baseline) and reintroduction (follow-up).The primary outcome was "satisfactory relief of gut symptoms" via the global symptom question; secondary outcomes included changes in stool consistency, IBS subtype, and gastrointestinal symptoms.Results: At baseline, 23.8% (70/294) had IBS-C and 35.7% IBS-D (105/294).All subtypes except IBS-M showed significant symptom relief at follow-up (P < 0.001), with no statistically significant difference between IBS-C (50.7%, 35/69) and IBS-D (44.8%, 47/105) (P = 0.158).After FODMAP restriction, 50.7% (35/69) IBS-C remained IBS-C, while 44.9% (31/69) shifted to unclassified IBS (IBS-U).Those who shifted (IBS-C to IBS-U) reported greater relief (74.2%, 23/31 vs 45.7% 16/35, P = 0.019) and reduced pain (P = 0.006), unlike those who remained IBS-C (P = 0.180).Conclusions: IBS-C and IBS-D showed similar symptom relief after FODMAP restriction.Notably, 44.9% of IBS-C patients shifted to normal stool consistency (IBS-U), with greater symptom relief and reduced pain.FODMAP restriction does not necessarily exacerbate constipation in IBS-C and remains a viable treatment option in real world clinical practice.