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Low FODMAPs Diet in IBS: Experts Disagree on Evidence of Efficacy

Interest in dietary interventions for irritable bowel syndrome has seen a recent revival, prompted by randomized controlled trial data suggesting elimination diets — namely, the gluten-free diet and the low fermentable oligo, disaccharides, monosaccharaides, and polyols, or low FODMAPs, diet — may be effective for treating patients. Emerging data on the potential efficacy of probiotics in IBS have also sparked increasing interest as the role of the gut microbiome in GI disorders becomes better understood.

This interest is not only limited to the scientific community, but also extends to patients; experts interviewed by Healio Gastroenterology estimated around three-quarters of their patients with IBS either ask about how diet may be affecting their symptoms, or have already tried a restrictive diet.

There seems to be a consensus that dietary therapies show promise for the treatment of patients with IBS, but data from rigorous randomized controlled trials, while compelling, remain sparse. The low FODMAPs diet currently has the greatest amount of available data, yet experts continue to disagree on whether or not enough is known about its efficacy to justify strong recommendation to patients with IBS.

Emerging Data

Last year, Paul Moayyedi, MBChB, PhD, MPH, director of the division of gastroenterology at McMaster University in Ontario, Canada, along with Eamonn Quigley, MD, chief of the division of gastroenterology and hepatology at Weill Cornell Medical College at Houston Methodist Hospital, and colleagues published results from a systematic review of randomized controlled trials published through December 2013, evaluating the efficacy of dietary restriction in patients with IBS. Based on three eligible trials — each respectively evaluating the low FODMAPs diet, the gluten-free diet and another exclusion diet — they concluded that elimination diets in general cannot be strongly recommended to patients with IBS until more evidence is accumulated.

Paul Moayyedi


In the first trial, 41 patients with IBS were randomly assigned to the low FODMAPs diet or their normal diet for 4 weeks, and while 68% of the low FODMAPs group reported adequate symptom control compared with 23% of controls (P = .005), the trial had a high risk of bias due to the unblinded design, Moayyedi and colleagues wrote. “The bottom line is most of these studies don’t give you the information you need to know whether [these dietary restrictions] are truly working in terms of improving patients’ overall symptoms,” Moayyedi told Healio Gastroenterology. “We simply don’t have enough evidence to say whether this works or not.”

William D. Chey

William D. Chey, MD, professor of medicine and nutrition sciences at the University of Michigan health system, director of the Digestive Diseases Center for Nutrition and Behavior at the University of Michigan, and Healio Gastroenterology Peer Perspective Board Member, said he disagrees with the authors’ conclusion that elimination diets cannot be recommended to patients with IBS. “While I agree at the time of their [study] it was fair to make that statement, a lot has happened in that intervening period of time,” he said in an interview. “First, people have gained a lot of clinical experience with diet therapies, and in general, I think the people who have been working with diet therapies would claim that a substantial proportion of their patients improve at least somewhat with diet strategies, whether you’re talking about the low FODMAPs diet or gluten-free diet. But more important than anecdotal clinical experience is the presentation of a number of different studies ... that seem to indicate a benefit for diet therapies.”

In one such study presented by Staudacher and colleagues at last year’s UEG Week, 104 patients were randomly assigned to receive low FODMAPs or sham dietary advice, and to the probiotic VSL#3 or placebo, for 4 weeks in a 2x2 factorial design. Intention-to-treat analysis showed 57% of the low FODMAPs group reported adequate symptom relief vs. 38% of the sham group (P = 0.05), as did 57% of the probiotic group vs. 37% of the plaebo group (P = 0.05). Mean IBS Symptom Severity Scale scores were also lower in the low FODMAPs vs. sham group (P < .001).