A double-blind study on the effect of purified cellulose dietary fiber on 1,2-dimethylhydrazine-induced rat colonic neoplasia.

The incidence, distribution, size, and histopathology of grossly visible colonic tumors induced by parenteral administration of 1,2-dimethylhydrazine were examined in rats fed either a chemically defined fiber-free diet or a nutritionally and calorically equivalent diet containing a purified fiber component, microcrystalline cellulose. This double-blind study indicates that cellulose ingestion was associated with reduced numbers of animals involved with colonic neoplasia as well as a reduction in the total numbers of colonic tumors. Furthermore, this protective effect of cellulose appears to be time dependent and associated with a shift in tumor distribution from the proximal colon to a more distal site. Cellulose fiber had no apparent effect on colonic tumor size, histopathology, or the incidence of other tumors known to occur in this experimental animal model. This study strongly supports the hypothesis that fiber is an important protective agent against colonic neoplasia development. While the mechanism for this protective effect remains obscure, it appears to be temporally related to the duration of fiber ingestion as well as to a differential fiber effect on either the luminal content or the mucosa of the proximal and distal colon.