Reduction of DMH-induced colon tumors in rats fed psyllium husk or cellulose

The effect of feeding psyllium husk, a water-soluble fiber, and cellulose, a water-insoluble fiber, against chemically induced colon cancer was investigated in rats. Adult male rats were fed semipurified diets containing 20% fat, no fiber, or 10% psyllium husk or cellulose for 22 weeks. Tumors were induced in one-half of the rats fed each diet by the gastric intubation of 1,2-dimethylhydrazine (DMH) during Weeks 3-11. In terms of the number of animals with tumors in each group, psyllium strongly reduced the tumorigenicity of DMH and cellulose moderately reduced tumorigenicity, whereas the two fibers did not differ significantly from each other with respect to tumorigenicity. Psyllium-fed rats had the highest fecal aerobic counts, lowest beta-glucuronidase, and highest 7-alpha-dehydroxylase activities. The psyllium diet also resulted in increased fecal output and percent moisture. Rats fed cellulose tended to have greater fecal bulk and lower beta-glucuronidase activity compared with rats fed no fiber and lower 7-alpha-dehydroxylase activity compared with rats fed psyllium husk.