American College of Physicians: Internal Medicine — Doctors for Adults ®


Does diet affect IBS?

Copyright 2003 by the American College of Physicians.

Ask experts if diet affects irritable bowel syndrome (IBS) and you'll get a definite "maybe."

Many IBS patients are afraid to eat certain foods for fear of triggering symptoms. But as Brian Lacy, MD, director of the Marvin M. Schuster Center for Digestive and Motility Disorders at Johns Hopkins Bayview Medical Center in Baltimore, Md., noted, "It's generally not what you eat but the act of eating that cause the symptoms." Besides, he continued, there are no good studies showing that dietary changes do anything to improve IBS.

Gastroenterologist Douglas A. Drossman, FACP, co-director of the University of North Carolina Center for Functional Gastrointestinal and Motility Disorders at Chapel Hill, however, said there is good evidence that eating too much of certain foods—those that contain caffeine or a lot of fat, for instance, or those that trigger gas production—can activate the bowel and worsen IBS symptoms. Patients with IBS are prone to excessive gut reactions to stressors, he pointed out, which can include dietary substances.

"Frequent small feedings, a low-fat diet and avoiding excess caffeine are rational and research-based recommendations," Dr. Drossman added.

He also recommended that patients keep a dietary record to see if any particular foods are linked to IBS symptoms. If so, patients can try to avoid those foods.

The problem is that many diet restrictions are impractical, noted George F. Longstreth, MD, chief of gastroenterology at Kaiser Permanente Medical Care Program in San Diego, Calif. And Dr. Lacy cautioned against creating "dietary cripples" by imposing excessive food taboos—and perhaps boosting stress that can worsen IBS symptoms.

Finally, while experts used to think a high-fiber diet could improve patients' diarrhea, pain and constipation, recent studies found that the strategy relieved only constipation. Researchers have also found that even that relief may come at a price: One study found that high-fiber diets increased symptoms of bloating in more than one-third of patients.


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