Fiber intake in different populations and colon cancer risk.

It has been suggested that consumption of fiber may reduce the risk for colon cancer. A negative association has been reported between national rates of mortality from colon cancer and estimates of dietary fiber from cereals, based on the fiber content of foods available in the national diets. Total dietary fiber consumption estimated from dietary surveys also was negatively associated with bowel cancer rates in a comparison of four regions of Denmark and Finland, and nonstarch polysaccharides were negatively associated with regional cancer rates in Britain. However, no association with estimates of fiber consumption has been observed in three case-control studies, and one case-control study reported a positive association between fiber intake and colorectal cancer among women. Other epidemiological investigations have examined the relationship between bowel cancer and use of cereals, fruit, and vegetables, foods that contain fiber as well as other nutrients but have failed to produce consistent results among investigations employing different study designs. The National Academy of Sciences found in 1982 that there was "no conclusive evidence to indicate that dietary fiber exerts a protective effect against colorectal cancer in humans," and the present data still do not satisfy the epidemiological criteria required to establish beyond doubt a protective effect of fiber. Nevertheless, dietary guidelines, such as those from the National Academy of Sciences, which recommend reduced fat consumption and increased consumption of cereals, fruit, and vegetables represent the current state of knowledge and form the basis of a diet that is unlikely to do harm and may have the potential for reducing cancer rates in North America.