Limited evidence to support low FODMAP diet in irritable bowel syndrome

Last Updated: 2015-08-13

By Will Boggs MD

NEW YORK (Reuters Health) - There is little strong evidence to support the use of a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) for treating irritable bowel syndrome (IBS), according to a recent review.

Undigested FODMAPs are thought to be rapidly fermented, resulting in increased luminal distension that may cause symptoms in IBS patients with visceral hypersensitivity. The aim of a low FODMAP diet is to reduce these symptoms.

The report, published online August 6 in Drug and Therapeutics Bulletin, discussed five studies of low FODMAP diets that yielded contrasting results.

A single-blinded, randomized controlled trial of 30 individuals (15 with IBS) reported higher gastrointestinal symptoms and lethargy in IBS patients on high FODMAP diets. Those on a low FODMAP diet reported decreased symptoms of abdominal pain, bloating, flatus, nausea, and lethargy.

Another randomized controlled single-blinded crossover trial of 30 IBS patients and eight healthy controls found significantly fewer overall gastrointestinal symptoms reported with a low FODMAP diet than with a typical Australian diet.

An unblinded randomized controlled trial of 41 IBS patients reported significantly higher rates of "adequate" symptom control with a restricted FODMAP diet than with continuation of their normal diet (p=0.005).

Another unblinded randomized trial of 123 adults with IBS found significant reductions in total IBS severity scores for a low FODMAP diet and for probiotic supplementation, compared with a normal Danish diet.

A nonrandomized controlled trial of 82 patients with IBS showed that significantly more patients who had been recommended a low FODMAP diet reported improvements in bloating, abdominal pain and flatulence, but not diarrhea, constipation, nausea, and energy level, compared with patients following a diet based on National Institute for Health and Care Excellence (NICE) guideline recommendations.

The review did not identify any published data that assessed the nutritional adequacy associated with a low FODMAP diet, but nevertheless warned that "potential harms from restrictive or exclusion diets could arise from nutritional inadequacy or harmful changes to the gut microbiota."

The British Dietetic Association classifies low FODMAP diets as second line interventions, whereas the British Society of Gastroenterology guidelines do not specifically mention FODMAPs. The most recent revision of the NICE guideline suggests offering advice on further dietary management of IBS if patients' symptoms persist while following general lifestyle and dietary advice. That advice could include low FODMAP diets.

The review concludes, "We believe that patients should be advised that there is very limited evidence for its use, the ideal duration of treatment has not been assessed in a clinical trial, and its place in the management of IBS has not been fully established."

Dr. Peter Gibson from Alfred Hospital in Melbourne, Australia, who pioneered the FODMAP hypothesis more than a decade ago, wrote in an email to Reuters Health, "The major criticism they offer is that there is no long term RCT evidence of efficacy. That will never occur as it is impossible to do (diet is not a drug)."

"There are no new or surprising findings," Dr. Satish Rao of the Digestive Health Center at the Medical College of Georgia in Augusta, who was not involved in this review, wrote in an email to Reuters Health. "They have concluded that more studies are required in better defined IBS populations and for longer period of time before advocating this treatment."

"FODMAPs diet is a fad and needs more research before this can be advocated to IBS patients," Dr. Rao concluded.

The Drug and Therapeutics Bulletin did not respond to a request for comment by press time.

SOURCE: http://bit.ly/1L8V0A9

Drug Ther Bull 2015.