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When Everyday Foods Are Hard to Digest

Complex Carbohydrates

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As many as 20 percent of adults at some point suffer from a painful digestive disorder that is difficult to diagnose and has no cure. Treatment is hit or miss, and many sufferers never seek help because they find the symptoms hard to discuss.

Irritable bowel syndrome (IBS) has long baffled gastro-intestinal experts. Some think it is caused by imbalances in gut bacteria; others point to psychological stress. Now, a small but growing contingent of specialists is focusing on food intolerances as a possible culprit—and a new dietary approach, called the low-Fodmaps diet, is gaining attention around the world.

The theory is that many people with IBS have trouble absorbing certain carbohydrates in their small intestines. Large molecules of those foods travel to the colon, where they are attacked by bacteria and ferment, creating the telltale IBS symptoms of gas, bloating, constipation or diarrhea.
A long list of foods—including dairy products, some fruits and vegetables, wheat, rye, corn syrup and artificial sweeteners—can potentially create such problems in susceptible people. 

Collectively, they're known as Fodmaps, an acronym that for stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.

Physicians have long known that some of these foods can cause stomach upset individually. About 15 percent of American lack an enzyme needed to digest lactose, a sugar found in milk products. There's now growing awareness that foods with a high concentration of fructose can be difficult to absorb. Breath tests that measure gas produced in the intestine can diagnose both of those issues, although they are more common in Australia than in the U.S.

Three other categories of sugars have also been found to cause absorption and fermentation problems in some people—including fructans that are found in wheat and rye, galactans that are found in legumes, and polyols, found in some fruits and in artificial sweeteners such as sorbitol and mannitol.

In fact, some experts say it's possible that people who do not have celiac disease but still have trouble digesting wheat products may actually be sensitive to the fructans in wheat rather than the gluten, which is protein component.

The low-Fodmaps diet recommends eliminating all of those foods for a period of six to eight weeks, and then gradually adding back one group after another to identify which cause the most trouble.

Eventually, many IBS sufferers find they can tolerate many foods on the list as long as they keep the total amount of Fodmaps under a certain level.

"It's not like having celiac disease, where people can't ever eat gluten," says Sue Shepherd, a dietician in Victoria, Australia, who developed the diet in 2001 mainly for patients with lactose or fructose intolerance, but found it worked well with IBS sufferers as well.

Click here to read more from the Wall Street Journal.