While our knowledge is still incomplete about the function and malfunction of the large bowel, some facts are well-known. Certain foods, such as coffee, alcohol, spices, raw fruits, vegetables, and even milk, can cause the colon to malfunction. In these instances avoidance of these substances is the simplest treatment.
Infections, illnesses and even changes in the weather somehow can be associated with a flare-up in symptoms. So can the premenstrual cycle in the female.
By far, the most common factor associated with the symptoms of IBS are the interactions between the brain and the gut. The bowel has a rich supply of nerves that are in communication with the brain. Virtually everyone has had, at one time or another, some alteration in bowel function when under intense stress, such as before an important athletic event, school examination, or a family conflict.
People with IBS seem to have an overly sensitive bowel, and perhaps a super abundance of nerve impulses flowing to the gut, so that the ordinary stresses and strains of living somehow result in colon malfunction.
These exaggerated contractions can be demonstrated experimentally by placing pressure- sensing devices in the colon. Even at rest, with no obvious stress, the pressures tend to be higher than normal. With the routine interactions of daily living, these pressures tend to rise dramatically. When an emotionally charged situation is discussed, they can reach extreme levels not attained in people without IBS. These symptoms are due to real physiologic changes in the gut -- a gut that tends to be inherently overly sensitive, and one that overreacts to the stresses and strains of ordinary living.