Inhibitory effect of small amounts of cellulose on colonic carcinogenesis with low-dose carcinogen.

This study set out to evaluate the effects of dietary fiber on cancer development in the large bowel under in vivo experimental conditions as similar as possible to those under which this cancer develops in vivo in humans. Forty-eight Sprague-Dawley rats were divided into three groups that were fed either a nonfiber diet or a 3 g or 10 g/100 g cellulose diet in this experiment, and all groups received doses of a mild carcinogen, 1,2-dimethylhydrazine (5 mg/kg body weight) for 50 weeks. Following endoscopic observation of the large bowel, we found that the induction rates of tumor in the cellulose groups were significantly lower than that in the nonfiber diet group, both endoscopically and histologically. No differences were seen between the 3% and 10% cellulose groups in suppressing carcinogenesis. It is likely that the inhibitory effect of 3% cellulose could be confirmed only by a long-term experiment on carcinogenesis following the administration of a low dose of carcinogen.