Constipation and Roughage Consumption

Lack of fiber in the diet was first postulated (假定) in 1971 as the cause of diseases such as diverticulosis (憩室病︰腸胃壁上的袋狀突出物), hemorrhoids and colorectal cancer. Since then, partly due to widespread media publicity, it is now widely accepted that dietary fiber is a necessary component of a healthy diet and is required for normal bowel movement. It is popularly used in the management of constipation by the public and by many doctors. Insoluble fiber is known to increase stool weight and decrease colonic transit time. Fiber is said to aid in water retention in the colon and results in stools that are less dry and easier to evacuate. However, the reality is that stool moisture content remains at 70%-75% regardless of the amount of fiber and water consumed.

There is recent evidence that low fiber intake does not equate to constipation. Patients with chronic constipation also have similar fiber intake to controls. Patients with chronic constipation may also have worsening symptoms when dietary fiber intake is increased. Another study found that lactulose (乳果糖) was more effective in easing constipation when compared with fiber.

It has also been our experience that many patients with constipation are already consuming a large amount of fiber before they seek medical attention.

Ho, K. S. (2012). Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms. World Journal of Gastroenterology, 18(33), 4593–4596. http://doi.org/10.3748/wjg.v18.i33.4593