In two small trials, certain FODMAPs were more likely to cause symptoms, and targeted elimination was effective.

Many patients with irritable bowel syndrome (IBS) can alleviate symptoms by consuming a diet low in fermentable oligo-, di- and monosaccharides and polyols (FODMAPs). However, following a low-FODMAP diet and the complex process of reintroducing foods to identify symptom triggers can be difficult, especially for patients without access to experienced nutritionists. In two US studies, researchers evaluated contributions of individual FODMAPs to patients’ symptoms.

In one study, 21 patients with IBS (median age, 30 years) whose symptoms improved during a two-week, open-label low-FODMAP period underwent blinded sequential reintroduction of five FODMAP components. The only statistically significant change in symptoms between low-FODMAP and reintroduction cycles was worsening of the mean abdominal pain score with fructan challenge. Mean bloating and abdominal pain worsened throughout the study regardless of reintroduction schedule; when authors looked only at the first challenge to eliminate this effect, pain increased significantly only for fructans and galacto-oligosaccharides, and bloating increased significantly only for galacto-oligosaccharides.

In another study, researchers compared ‘simple’ FODMAP restriction (eliminating only fructans and galacto-oligosaccharides) to a ‘traditional’ low-FODMAP diet in 32 patients. The proportion of patients in each group who had symptom responses was similar (10 of 16 in the simple group and nine of 16 in the traditional group). A per-protocol analysis showed greater mean decrease in symptom severity in the traditional group, but this was offset by a higher dropout rate due to adherence and tolerability issues.

Comment: These results suggest that fructans and galacto-oligosaccharides might be particularly likely to cause IBS symptoms and that targeted elimination of these components might be as effective as eliminating all FODMAPs. Although these small trials are not definitive, clinicians reasonably could offer this simpler, two-element approach to patients who express interest in trying dietary modification for IBS.

Sarah E. Post, MD, Lecturer in Medicine, Harvard Medical School; Internal Medicine Physician, Atrius Health, Boston, USA.

Eswaran S, et al. All FODMAPs aren’t created equal: results of a randomized reintroduction trial in patients with irritable bowel syndrome. Clin Gastroenterol Hepatol 2025; 23: 351-358.

Singh P, et al. Is a simplified, less restrictive low FODMAP diet possible? Results from a double-blind, pilot randomized controlled trial. Clin Gastroenterol Hepatol 2025; 23: 362-364.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Gastroenterology.