It is not known for certain what causes functional diseases such as Irritable Bowel Syndrome, but there are several theories. It seems obvious that the muscles that control the contractions of the organs that produce bowel movements don't operate in the way that they are supposed to, but it is not so easy to determine which of the areas involved are responsible for the disease. Since there are different nerves and organs involved in the sensing and responding events, it is difficult to pinpoint which point of the process is causing the wrong message or wrong response to result in contractions of the bowel.

There are both sensory and motor nerves that communicate to cause muscular functions in the body, including the gastrointestinal tract. The sensory nerves carry messages from the organs to the spinal cord and then to the brain. The brain sends out a response which is carried through the spinal cord and then to the muscle of the organ involved. If your shoe is hurting your foot when you walk, the sensory nerves feel the pain and send the signal to the brain that you feel pain in your foot. The brain then sends a message to remove the shoe that is causing you pain. This series occurs in a very short time, the time it takes to pull your hand back from a source of heat. It has been theorized that Irritable Bowel Syndrome is a result of a miscommunication somewhere along this series of events, but no one knows for sure where the problem originates. It may occur in the sensory or motor nerves, the organ, the spinal cord, or the brain.

If the abnormality occurs with the sensory nerves, then normal activities might send the signal that your body is feeling pain when it isn't. Your brain might respond by sending a signal for a contraction of the bowel to relieve the pain. An abnormal command that is carried through the motor nerves can cause a response such as a painful contraction of a muscle to take place. There are also some people who believe that it is a combination of motor and sensory dysfunction that leads to IBS.

Since people who have been diagnosed with Irritable Bowel Syndrome have larger amounts of gas than those who have not been diagnosed, this is an area of interest to researchers looking to find the cause of the disease. The gas usually remains longer in the small intestine and the abdominal size increases throughout the day until it peaks in size in the evening and returns to its regular size by the following morning. Since the ingestion of certain types of foods is also know for an increase in gas, these foods are also considered a possible irritant to people with Irritable Bowel Syndrome. Those who are lactose intolerant and have consumed large amounts of dairy foods know how it can affect your bowels. This is especially true in those with IBS.

Dietary sugars also pose a possible threat to those with IBS. Fructose is a common additive to make foods sweeter and it is often poorly digested. Since these unabsorbed sugars can increase the production of gas in most individuals, it is arguable as to whether the fructose causes irritation to IBS sufferers or is the same with everyone. The affect of these food additives is unproven for their affect on IBS sufferers but this is a common theory.

The reduction of some foods may or may not be an effective prevention for the symptoms of IBS, but that is not the same as a prevention or cure for the disease. Reducing dietary fat may help alleviate symptoms as well, and will definitely improve your overall health and nutrition