Neil Osterweil

October 27, 2015

HONOLULU — Despite the number of diets that purport to help people with irritable bowel syndrome, rigorous evidence supporting their use is lacking, experts said here at the American College of Gastroenterology 2015 Annual Meeting.

When it comes to diet, "patients are leading the way," said William Chey, MD, from the University of Michigan at Ann Arbor. "They are proactively coming in and asking about diets, or they're already on diets, or they're seeing some type of alternative healthcare provider who has recommended a diet."

"It's difficult for physicians who perhaps don't spend a lot of time reading about this space to sift through all the noise," he pointed out.

Dr Chey likened the current situation to the 1990s television cult classic The X-Files, in which FBI special agents track down menacing paranormal phenomena. The show "would take some popular theme and sprinkle just enough pseudo-science on it to make it believable," he explained.

"I think that's exactly what's happening with a lot of diets; people sort of spread around a little bit of special sauce, a little bit of magic dust, say that it's 'clinically proven,' and then suddenly patients believe it as scientifically validated," he said. "Unfortunately, there are very few data supporting the various diets that are being used by patients with GI illness right now."

Secret Sauce and Magic Dust

"That doesn't mean that diets don't work. The problem is that we don't know one way or the other. What we really need to do is to apply the same scientific rigor that we do to pharmaceuticals," said Dr Chey.

He reviewed what is known and what is conjecture about the role of diet in the management of irritable bowel syndrome.

There is no standardized diet, he said, although patients are frequently counseled to avoid excess caffeine, chocolate, alcohol, lactose, sorbitol, fatty foods, and junk foods. Patients with hard stools are encouraged to bulk up their diets with fiber and to allow sufficient time and quiet for meals.

People with celiac disease are seriously affected by gluten, a storage protein found in the endosperm of wheat kernels.

However, the vast majority of the people who shun gluten do not have celiac disease. And the food and beverage industry is cashing in on the craze, flogging everything from gluten-free beer to gluten-free dog food, Dr Chey pointed out.

The prevalence of gluten sensitivity or wheat sensitivity — which can be clinically indistinguishable from celiac disease but will yield negative or inconclusive results on celiac testing — is not known. Most of these patients report improvement with gluten-free diets.

Gluten itself might not be the problem in nonceliac disorders. It has been suggested that short-chain carbohydrates, also known as FODMAPs — fermentable oligo-, di-, monosaccharides and polyols — are the culprit.

The consumption of FODMAPs is thought to induce symptoms of GI pain, gas, bloating, and altered bowel movements. A complex series of osmotic effects leads to the acceleration of food transit, bacterial fermentation, and the production of short-chain fatty acids, which in turn lead to gas production, changes in motility, visceral sensation, immune activation, and bowel permeability.

More Fructose Than Glucose

Fruits in which the amount of fructose exceeds the level of glucose, such as apples, pears, watermelons, contain FODMAPs, as do vegetables containing fructan, a polymeric chain of fructose molecules, such as onions, leeks, asparagus, and artichokes.

Wheat-based products, such as pasta, bread, cereal, cake, biscuits, foods containing sorbitol and lactose, and foods containing the trisaccharide raffinose, such as legumes, lentils, cabbage, and Brussels sprouts, can all cause problems.

One study showed that after eating a diet high in FODMAPs for 2 days, 30 patients with irritable bowel syndrome experienced significantly higher levels of breath hydrogen production (a sign of lactose, glucose, or fructose intolerance) and increased GI symptoms and lethargy (J Gastroenterol Hepatol. 2010;25:1366-1373), Dr Chey reported.

And a crossover study showed that 21 days of a low-FODMAP diet led to a significant reduction in overall symptoms, bloating, pain, and gas in 30 patients with irritable bowel syndrome and 8 healthy volunteers (Gastroenterology. 2014;146:67-75.e5).

But eating a low-FODMAP diet is not as easy as simply eliminating gluten from the diet, cautioned Paul Moayyedi, MD, director of the division of gastroenterology at McMaster University in Hamilton, Ontario, Canada.

Forbidden Foods

"It's strict, so this is not easy for patients. The number of foods that they aren't allowed to consume is huge," he said.

For example, corn syrup is contraindicated in a low-FODMAP diet, but maple syrup is okay. This is not a problem if you live in Canada or New England, but is a costly proposition elsewhere, he pointed out.

"We really need to know whether this works or not," he said. "We find something new and think it's wonderful, then someone else does a study and we realize it's all poison and awful. Eventually we come to some sort of evidence on whether this is worthwhile or not."

"I don't view the FODMAP diet as the end of the story at all," Dr Chey countered. "I view the FODMAP diet as a mechanism that establishes the potentially important role of diet in GI symptoms."

Dr Chey reports financial relationships with Actavis, Arelyx, Asubio, Astra-Zeneca, Forest, Ironwood, Nestle, Prometheus, Salix, Sucampo, Takeda, and Vibrant. Dr Moayyedi reports relationships with AstraZeneca, Forest Laboratories, and Shire Canada.

American College of Gastroenterology (ACG) 2015 Annual Meeting. Presented October 19, 2015.

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