Effect of Types of Dietary Fiber on Fecal Mutagens and Bacterial Enzymes in Relation to Colon Cancer

Abstract

Large bowel cancer affects men and women in Western coutries, including United States and Canada, with high frequency (1,2). Since Wynder et al. (3) first provided an evidence for an association between colon cancer and consumption of a more westernized diets including more fat in Japan, there have been several epidemiologic and animal model studies to test this hypothesis. The hypothesis that a diet high in fiber may protect against colon cancer was first proposed by Burkitt and Trowell (4) who observed that African blacks consuming high fibrous foods had lower death rates due to colon cancer than their white counterparts eating a low fiber diet. Subsequent studies demonstrated that, in certain populations consuming diets high in total fat, the intake of diets high in total fiber, fibrous foods, and certain whole grain foods has been associated with a reduced risk for colon cancer (5,6). A majority of international studies provided evidence for protective effect of dietary fiber and fibercontaining foods (7). Recent intracountry comparisons of dietary fiber and colon cancer mortality rates strongly supported the hypothesis that dietary fiber protects against colon cancer (8). Colon cancer incidence data from Scandinavian countries show a gradient of risk, with the lowest risk in rural areas in northern Finland (Kuopio and Parikkala), increasing to urban Helsinki, and highest in Copenhagen, Denmark (9,10). Finnish population consume diets high in fat, mainly saturated fat; but the low incidence of colon cancer in rural Finland may be explained in part by their consumption of diets high in fiber mainly from whole grain cereals and bread (10,11).