Influence of a dietary fiber on development of dimethylhydrazine-induced aberrant crypt foci and colon tumor incidence in Wistar rats.

Formation of aberrant crypt foci (ACF) in archived colon tissue from animals in a previous study was examined. The animals were fed a semisynthetic casein-based diet in which the carbohydrate pool was substituted with a dietary beet fiber (Fibeta) as the only source of fiber. Oral doses of dimethylhydrazine dihydrochloride (DMH-2HCl, 20 mg/kg body wt) once a week for 10 weeks were used as initiator. The rats were fed different levels of the fiber in a preinitiation period, during initiation, or in a postinitiation period. In general, the results showed a statistically significant inverse relation between duration of intake of high-fiber diet and number of animals with ACF, as well as the total number of ACF and number of small ACF (1-3 crypts) per affected animal. The previously reported data showed no protective effect of the dietary fiber at any stage of the colorectal carcinogenic process. The lack of correlation between the outcome of ACF and tumors could be related to the observation that statistically significant differences between groups were seen only in the total number of ACF and number of small ACF. The hypothesis that ACF are preneoplastic lesions needs to be supported by further experimental data. The present state of knowledge could indicate that ACF represent true preneoplastic lesions progressing into colon tumors or that ACF and colon tumors represent two parallel independent events as a consequence of the cancer initiation (i.e., the ACF not being preneoplastic lesions per se).