Ask Dr. K: Irritable bowel

DEAR DOCTOR K: I have irritable bowel syndrome. Can you explain what has caused it?

DEAR READER: The honest answer is we don’t know what causes irritable bowel syndrome. Over the past 20 years, we’ve discovered some clues and developed some new treatments.

IBS is a common condition. Symptoms include abdominal pain, diarrhea and/or constipation, bloating, gassiness and cramping.

No physical abnormality has been yet identified in people with IBS. For example, the walls of the large and small intestine appear normal. However, researchers have reported some abnormalities in how the intestines function.

Some possible causes of IBS symptoms include:

• Infection. A bout of infectious gastroenteritis (stomach or bowel inflammation) may sensitize the gut in a way that leads to IBS symptoms.

• Overgrowth of intestinal bacteria in the small intestine. This may contribute to common symptoms in some patients, and antibiotic treatment may improve some symptoms.

• Unusual bacteria in the large intestine. In all of us, the large intestine is filled with trillions of bacteria, of thousands of different types.

• Colon activity. Some research has found that muscle in the wall of the large intestine (colon) can become more sensitive than usual; it goes into spasm after only mild stimulation.

• Hormones produced in the GI tract, which affect movement of the bowels, may also trigger symptoms. Women with IBS often have more symptoms during their menstrual periods. This suggests that levels of reproductive hormones also affect IBS symptoms.

• Dietary factors. Certain foods can trigger IBS symptoms. Common culprits include cabbage, broccoli, legumes and other gas-producing foods, caffeine, alcohol, dairy products, fatty foods, raw fruits, and foods, gums and beverages containing sorbitol, an artificial sweetener. These foods contain substances called FODMAPs. It’s a matter of trial and error to determine which foods trigger your symptoms. Eliminate one food at a time to see which ones give you trouble.

• Stress and emotion. Stress stimulates colon spasms in people with IBS. Stress reduction, relaxation training and counseling can help relieve symptoms in some people.