What causes diverticular disease?
Diverticular disease essentially results from eating a diet with too little fiber. Fiber is the part of fruits, vegetables, and grains that the body cannot digest. Fiber itself is not digested. It passes through the intestines pretty much unchanged, softening the stools and their passage. Lack of fiber begins a sequence of events:
Without fiber, the stools are dry and small, and the intestinal muscles must contract with greater force to pass the stools along, generating a higher pressure in the large intestines. The excess pressure leads to weak spots in the colon walls that eventually bulge out and form pouches called diverticula.
Existing weakness in the colon walls-either from age or, in younger people, or from collagen disorders like Marfan's syndrome-also contribute to the development of diverticula. Most often, the pouches form in the sigmoid colon, which is the lower left part of the colon that connects to the rectum. This area of the colon is subject to the highest amount of pressure because it is the narrowest portion of the large intestine. Soluble fiber dissolves easily in water and takes on a soft, jelly-like texture in the intestines. Insoluble fiber passes almost unchanged through the intestines. Both kinds of fiber help make stools soft and easy to pass, which helps to prevent constipation.
Constipation is the main cause of increased pressure in the colon, making the muscles strain to move stool that is too hard. The excess pressure caused by the straining makes the weak spots in the colon bulge out, forming diverticula.
There is a familial tendency to diverticulosis suggesting a genetic factor. An inherited tendency to raised pressure in the bowel has not yet been associated with a gene. It may be that these families share a common environmental factor increasing their susceptibility to high intra-bowel pressure.
The relatively high prevalence of diverticula in an aging Western population compared with the low prevalence in developing countries with a high vegetable diet supports the current theory that a diet low in plant products is a factor in the pressure changes needed to produce diverticula. This is the most generally discussed cause of diverticular disease providing the basis for much of the advice given to reduce the prevalence of diverticular disease as well as the management of established diverticular disease.
Some foods and drugs are strong stimulants of bowel muscle action and may be an aggravating factor. Such foods include spices, fats and some sauces. The importance of emotional stress is unresolved. While not strongly favoured as a cause, it may be an aggravating factor that cannot be completely excluded as a cause. Physicians do not know what causes the infection that causes diverticulitis, but believe it may begin when stool or bacteria are caught in the diverticula.