Effectiveness of the Low Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols Diet for Patients With Irritable Bowel Syndrome Managed in Primary and Secondary Care: A Systematic Review and Meta-Analysis of Randomized Trials

The low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet has emerged as a promising dietary intervention for managing irritable bowel syndrome (IBS) symptoms.We aimed to evaluate the effectiveness of the low FODMAP diet compared with various control conditions in adults with IBS.The pre-specified primary outcome was the Irritable Bowel Syndrome Symptom Severity Score, whereas adequate relief, abdominal pain, bloating, and quality of life (QoL) were the secondary outcomes.A systematic search identified English-language randomized controlled trials (RCTs) from inception through 20 May 2026 that compared the low FODMAP diet with control conditions in adults with IBS.Statistical analyses were performed using RevMan 5.4 (Cochrane Collaboration, London, UK), with treatment effects expressed as standardized mean differences (SMDs) or odds ratios (ORs) with 95% confidence intervals (CIs).Heterogeneity was quantified using the I² statistic, and random-effects models were used for the primary analyses, with fixed-effect sensitivity analyses when heterogeneity was low.Twenty-three RCTs, encompassing 2,164 participants (1,852 completers), were included.Compared with traditional dietary advice, the low FODMAP diet significantly reduced IBS symptom severity score (SMD: -0.71; 95% CI (-1.02, -0.40)), improved adequate relief (OR: 2.15; 95% CI (1.54, 3.01)), reduced abdominal pain (SMD: -0.35; 95% CI (-0.54, -0.16)), decreased bloating (SMD: -0.45; 95% CI (-0.75, -0.15)), and improved QoL (SMD: 0.48; 95% CI (0.27, 0.69)).Similar benefits were observed against habitual diet comparators.Compared with other active dietary interventions, the low FODMAP diet did not significantly improve IBS symptom severity, adequate relief, or QoL, although it did modestly improve bloating.The low FODMAP diet is an effective intervention for reducing global IBS symptoms and improving QoL compared with traditional dietary advice and habitual diet; however, it does not appear to offer greater benefit than other structured active dietary interventions, aside from this modest, comparator-independent improvement in bloating.These findings suggest that structured dietary intervention and dietary support may contribute substantially to symptom improvement beyond FODMAP restriction itself.