Are dietary fiber-induced alterations in colonic epithelial cell proliferation predictive of fiber's effect on colon cancer?

Alterations in cell proliferation of the colon have been observed as a resu lt of changes in amount and type of dietary fiber and in relation to risk o f developing colon cancer. Although some human observational and interventi on studies contribute to the database, most information results from experi ments on rodents. Because of numerous contradictory reports linking dietary fiber, cell proliferation, and colon cancer, we undertook a critical revie w of existing methods in an attempt to explain the inconsistencies. Althoug h there may be some individual types of dietary fiber that protect against chemically induced colon cancer, dietary fiber as a single entity does not appear to afford any consistent protection. Because of significant differen ces in experimental protocols among laboratories, it is not yet possible to state with certainty that increases in cell proliferation, induced by fibe r consumption, are predictive of increased tumorigenesis. Much of what has been observed and interpreted as elevation of risk may simply be normal hom eostatic changes in cell proliferation. Even though fermentation to short-c hain fatty acids is a mechanistically attractive hypothesis to explain why fiber modulates cytokinetics, data do not consistently support short-chain fatty acids as biological intermediates in risk of colon cancer. The state of the art in this field has not yet progressed to the point where a clear effect of dietary fiber on cytokinetics and colon carcinogenesis can be ass essed with any degree of certainty. Additional markers of apoptosis, differ entiation, and cell-cell communication may be required for a more accurate analysis of the relation among fiber, cytokinetics, and colon cancer.