Irritable Bowel Syndrome - Causes

The food a person eats passes through various stages of digestion. In the stomach and small intestine, food is changed into a liquid. In the large intestine (colon), water and salts in this liquid pass through the walls of the colon into the bloodstream. The semisolid material that remains is passed on to the rectum.

Food is passed through the digestive system by means of peristalsis (pronounced per-i-STOL-sis). Peristalsis is a wave-like series of movements made by muscles in the walls of the digestive system. Peristalsis in the colon usually occurs only after meals.

In people who have IBS, peristalsis occurs in unusual patterns. It may go on for extended periods of time, or it may take place much more slowly than usual. In the first case, watery solids are continually passed to the rectum, which results in diarrhea. In the second case, very dry solids are passed to the rectum, which leads to constipation. Irritable bowel syndrome is any condition in which the colon does not function normally.

Certain foods seem to cause IBS in some people. They include chocolate, milk products, caffeine, and large quantities of alcohol. Some individuals are affected by very specific foods. Stress is also related to IBS. People who have IBS are likely to develop symptoms when they feel anxious. Researchers do not yet know why this connection exists.