Causes of Irritable Bowel Syndrome (IBS)

Researchers have yet to discover any specific cause for IBS. One theory is that people who suffer from IBS have a colon (large bowel) that is particularly sensitive and reactive to certain foods and stress. The immune system, which fights infection, may also be involved.

Normal motility, or movement, may not be present in a colon of a person who has IBS. It can be spasmodic or can even stop working temporarily. Spasms are sudden strong muscle contractions that come and go.

The lining of the colon called the epithelium, which is affected by the immune and nervous systems, regulates the flow of fluids in and out of the colon. In IBS, the epithelium appears to work properly. However, when the contents inside the colon move too quickly, the colon looses its ability to absorb fluids. The result is too much fluid in the stool. In other people, the movement inside the colon is too slow, which causes extra fluid to be absorbed. As a result, a person develops constipation.

A person’s colon may respond strongly to stimuli such as certain foods or stress that would not bother most people.

Recent research has reported that serotonin is linked with normal gastrointestinal (GI) functioning. Serotonin is a neurotransmitter, or chemical, that delivers messages from one part of your body to another. Ninety-five percent of the serotonin in your body is located in the GI tract, and the other 5 percent is found in the brain. Cells that line the inside of the bowel work as transporters and carry the serotonin out of the GI tract. People with IBS, however, have diminished receptor activity, causing abnormal levels of serotonin to exist in the GI tract. As a result, people with IBS experience problems with bowel movement, motility, and sensation—having more sensitive pain receptors in their GI tract.

In addition, people with IBS frequently suffer from depression and anxiety, which can worsen symptoms. Similarly, the symptoms associated with IBS can cause a person to feel depressed and anxious.

Researchers have reported that IBS may be caused by a bacterial infection in the gastrointestinal tract. Studies show that people who have had gastroenteritis sometimes develop IBS, otherwise called post-infectious IBS.

Researchers have also found very mild celiac disease in some people with symptoms similar to IBS. People with celiac disease cannot digest gluten, a substance found in wheat, rye, and barley. People with celiac disease cannot eat these foods without becoming very sick because their immune system responds by damaging the small intestine. A blood test can determine whether celiac disease may be present.

The following have been associated with a worsening of IBS symptoms
  • large meals
  • bloating from gas in the colon
  • medicines
  • wheat, rye, barley, chocolate, milk products, or alcohol
  • drinks with caffeine, such as coffee, tea, or colas
  • stress, conflict, or emotional upsets
Researchers have found that women with IBS may have more symptoms during their menstrual periods, suggesting that reproductive hormones can worsen IBS problems.
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Source:
Topic Excerpted from: Irritable Bowel Syndrome. National Digestive Diseases Information Clearinghouse (NDDIC). National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). National Institutes of Health. NIH Publication No. 06–693: February 2006