Efficacy and Acceptability of Dietary Therapies in Non-Constipated Irritable Bowel Syndrome: A Randomized Trial of Traditional Dietary Advice, the Low FODMAP Diet, and the Gluten-Free Diet

Background & Aims\ud \ud Various diets are proposed as first-line therapies for non-constipated irritable bowel syndrome (IBS) despite insufficient or low-quality evidence. We performed a randomized trial comparing traditional dietary advice (TDA) against the low FODMAP diet (LFD) and gluten-free diet (GFD).\ud \ud \ud \ud Methods\ud \ud Patients with Rome IV-defined non-constipated IBS were randomized to TDA, LFD, or a GFD (the latter allowing for minute gluten cross-contamination). The primary endpoint was clinical response after 4 weeks of dietary intervention, as defined by ≥50-point reduction in IBS symptom severity score (IBS-SSS). Secondary endpoints included i) changes in individual IBS-SSS items within clinical responders, ii) acceptability and food-related quality of life with dietary therapy, iii) changes in nutritional intake, iv) alterations in stool dysbiosis index, and v) baseline factors associated with clinical response.\ud \ud \ud \ud Results\ud \ud The primary endpoint of ≥50-point reduction in IBS-SSS was met by 42% (n=14/33) undertaking TDA, 55% (n=18/33) for LFD, and 58% (n=19/33) for GFD; p=0.43. Responders had similar improvements in IBS-SSS items regardless of their allocated diet. Individuals found TDA cheaper (p