The idea that chronic constipation is the result of a low-fiber diet may be one of the many myths and misconceptions about the condition, according to a new review of the issue.

The same is true of the idea that consuming more fluids will ease constipation, or that those who rely on laxatives will become dependent on them.

“Defecation is a very private process rarely discussed with the physician but more easily discussed with friends,” study author Dr. Stefan A. Muller-Lissner of Humboldt University in Berlin told AMN Health.

“Therefore it is prone to unsubstantiated theories and beliefs derived from subjective impressions and unsystematic observations.”

He said “the role of fluid and dietary fiber intake is overemphasized and there is an unsubstantiated fear that laxative intake in reasonable doses were unhealthy,”

Muller-Lissner and his colleagues address some of the notions about constipation in a report published in the American Journal of Gastroenterology.

They first debunk the myth that chronic constipation may lead to autointoxication from the absorption of poisonous substances backed up in the colon.

This belief was held even among the ancient Egyptians, according to an inscription dating back to the 16th century B.C., and in the early 20th century a famous London surgeon asserted that all chronic diseases result from autointoxication. Yet, there is no current evidence to support such a theory, write Muller-Lissner and his team, adding that some people continue to undergo regular “colon cleansing” with laxatives and enemas.

Fiber is known to add bulk to stool and to increase the frequency of bowel movements, and many people believe that a low-fiber diet can cause constipation. Available research suggests people should not assume this to be true, however, although a diet that is poor in fiber may indeed contribute to chronic constipation.

A high-fiber diet may alleviate the condition in some patients, the researchers note, but those with severe constipation may experience worsened symptoms upon increasing their fiber intake.

In considering whether constipation is caused by a low intake of fluids or if it can be improved by increasing fluid intake, Muller-Lissner and his team report that there is no evidence to support either belief. Unless a person is dehydrated, increasing fluid intake does not appear to treat constipation, their review findings indicate.

The researchers also look into the possibility that a sedentary lifestyle contributes to constipation and that physical activity may be beneficial.

After reviewing several studies on the topic they conclude that physical activity may affect bowel function, but other factors such as diet and personality may also play a role. Programs designed to increase physical activity may not improve bowel function among young patients with severe constipation, but may help elderly individuals, when combined with other aspects of “a broad rehabilitation program,” the authors write.

Muller-Lissner and his team also investigate various claims about the chronic use of laxatives, including the idea that it may cause nerve or muscle damage in the colon, may increase the risk of various cancers, including colorectal cancer, and may cause users to become dependent on laxatives.

Claims of nervous system damage caused by laxatives have been based on “poorly documented experiments,” they write, adding that it is “unlikely” that laxatives taken at recommended doses will harm the colon.

Also, while chronic constipation does appear to be associated with increased colorectal cancer risk, there is no evidence that the use of laxatives independently increases a person’s risk of the cancer.

As for the risk of developing dependency on laxatives, there is no such potential, Muller-Lissner and his colleagues state, although they acknowledge that psychiatric patients may misuse them.

Individuals affected by constipation should “not be bothered by a low stool frequency as such,” Muller-Lissner concluded. “Try fiber,” he advised, “and use laxatives if this does not work sufficiently.”

SOURCE: American Journal of Gastroenterology, January 2005.