Irritable Bowel Syndrome: Causes

What causes irritable bowel syndrome?

The exact cause of irritable bowel syndrome (IBS) has not been determined, although there are several theories. One theory is that IBS may be an immune disorder, or one in which the intestines of the affected person are highly sensitive in responding to stress and bacteria. Certain foods are thought to trigger IBS flare-ups, including dairy products and gluten, which is present in wheat, barley and rye.

The epithelial layer, or lining, of the large intestine controls the amount of fluid in the bowel. In IBS, there appears to be a disruption in the function of fluid absorption. This can result in excessive fluid in the colon, which causes diarrhea and watery stools. Or, if the lining of the colon absorbs too much fluid from the colon contents, the stool may become dry, leading to constipation.

Bacteria in the intestinal tract have been found to have a connection to IBS. Some people develop IBS following bacterial gastroenteritis, an inflammation of the gastrointestinal (GI) tract caused by a bacterial infection.

Another theory of IBS points to a potential role of serotonin, a chemical that transmits nerve signals from one part of the body to another. Excessive levels of serotonin may result in diminished bowel movement and motility function, producing the symptoms of IBS.

What are the risk factors for irritable bowel syndrome?

A number of factors increase the risk of developing irritable bowel syndrome (IBS). Not all people with risk factors will get IBS. Risk factors for IBS include:

• Feelings of stress
• Female gender
• Ingestion of certain foods, such as dairy products or gluten
• Previous gastrointestinal infections such as gastroenteritis