Are Dietary FODMAPs a Cause of Irritable Bowel Syndrome?

Summary and Comment |
January 28, 2014

Are Dietary FODMAPs a Cause of Irritable Bowel Syndrome?

  1. Allan S. Brett, MD and
  2. Douglas K. Rex, MD

In a randomized trial, IBS symptoms improved with a diet low in these short-chain carbohydrates.

  1. Allan S. Brett, MD and
  2. Douglas K. Rex, MD

The idea that dietary constituents called FODMAPs (Fermentable, Oligo-, Di-, Monosaccharides, And Polyols) might be responsible for some cases of irritable bowel syndrome (IBS) is gaining traction. FODMAPs are poorly absorbed, short-chain carbohydrates that include fructose, lactose, fructans (found in wheat), galactans, and polyol sweeteners.

In this randomized, crossover trial from Australia, 30 patients who met IBS criteria and 8 healthy controls consumed either a low-FODMAP diet (prepared by the researchers) or a “typical Australian diet” for 3 weeks, followed by the opposite diet for another 3 weeks; the two diet periods were separated by a 3-week washout. Patients were blinded to diet constituents.

At baseline, the mean symptom score for IBS patients was 36 (on a 100-point scale); mean scores declined to 23 during the low-FODMAP period and increased to 45 during the typical-diet period — a highly significant difference (P<0.001). Regardless of IBS subtype, patients were more satisfied with stool consistency during the low FODMAP diet. In controls, symptom scores were low at baseline and did not change during either diet period.


This is the first randomized trial to provide high-quality evidence that FODMAPs contribute to irritable bowel symptoms. One potential confounding dietary constituent is gluten, because a low-FODMAP diet (which eliminates wheat, rye, and barley because of their fructan content) is also low in gluten; however, in a recent study by the same research group, FODMAPs — and not gluten — likely were responsible for gastrointestinal symptoms in nonceliac patients with perceived gluten sensitivity (NEJM JW Gen Med Sep 19 2013). Information on low-FODMAP diets is available from this research team's institution and from other sources (e.g., Stanford University). Clinicians should consider recommending a low-FODMAP diet to IBS patients with abdominal bloating, flatus, and diarrhea.

Editor Disclosures at Time of Publication

  • Disclosures for Allan S. Brett, MD at time of publication Nothing to disclose

  • Disclosures for Douglas K. Rex, MD at time of publication Consultant / Advisory board Exact Sciences; Ferring Pharmaceuticals; Given Imaging; Olympus Speaker’s bureau Boston Scientific; Braintree; Ferring Pharmaceuticals Grant / research support Battelle; Braintree; Northwestern University; Olympus America Editorial boards Annals of Gastroenterology and Hepatology; Comparative Effectiveness Research; Expert Review of Gastroenterology and Hepatology; Gastroenterology; Gastroenterology and Hepatology News; Gastroenterology Report; Gastroenterology Research and Practice; Journal of Clinical Gastroenterology; Techniques in Gastrointestinal Endoscopy; World Journal of Gastroenterology; World Journal of Gastrointestinal Oncology; World Journal of Gastrointestinal Pathophysiology; World Journal of Gastrointestinal Pharmacology and Therapeutics


Reader Comments (6)

Tina Lee Other Healthcare Professional, Palliative Medicine

Validation at last. I have had many people say they are gluten intolerant only to discover they have no symptoms from eating high-gluten protein substitutes. I have long suspected it was some other contributing factor in wheat, as their symptoms do subside when wheat is restricted. Incidentally, one client claims fewer symptoms with genuine sourdough bread. Would the souring process alter FODMAPS? Oats are not mentioned in the study; do we have information on FODMAPS in oats?

John McBride Other, Other, Environmental;Indoor Health Consultant

This is interesting as many whom are affected by environmental illnesses due to mold/bacteria growth; also do much better on low carb. diets. In fact antifungal diets specifically require low carb, no sugar diets. Now research has shown grains such as wheat not only possess gluten proteins which at best are digestive irritants, they also are full of mycotoxins which directly cause digestive issues. This also includes corn which is glycemic and a fungal favorite as a result. Now those exposed and made ill to mold become gluten intolerant and also get diagnosed with IBS. This is only one of the many illnesses caused by indoor mold growth. Dairy is also to be avoided for the same mycotoxic reasons. Intestinal inflammation, kidney, and liver damage are also just some systems that are affected and damaged. Good flora imbalances and increased innate immune responses lead to chronic inflammation. This year alone many peer reviewed papers have been published not to mention the 248 page report that was released in 2009” by the World Health Organization. For those who would like to learn more please feel free to contact me and I would be glad send the medical literature on this.

JUERGEN SCHIEFERMUELLER Fellow-In-Training, Cardiology

High-quality evidence from a study of 30 patients?? You are joking, right?

juso prelo Physician, Gastroenterology

keep doing cardiology, don´t try to onderstand medicine

Richard Herold MD Physician, Internal Medicine, out patient office

It is certainly not scientific but I know 3 people with similar symptoms to the study patients who have all had total resolution by avoid only wheat and grain products. I have told a few patients to try it who haven't responed to other things (still waiting to see how they did), but I would love to see larger studies.

Mandar Kelkar Other, Pharmacology/Pharmacy

Clinical pharmacologist by profession.

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