Fiber and cancer protection--mechanisms

There is no reason to believe that a single lumenal or tissue factor will hold the key to understanding the of dietary fiber's effect on reducing the risk of colon cancer. In fact, the data suggest that multiple, interacting factors will be revealed. After years of research, it appears that the bile acid hypothesis is not nearly as strong as first envisaged. Additionally, the theory that SCFA protect against colon cancer has little clinical or experimental support. There is no doubt that identification of genetic alterations, and their controlling factors, will play a major role in our understanding of this issue. The appeal of the original fiber hypothesis has not diminished but simply requires updating based on discoveries made since it was first proposed. It is this author's opinion that dietary fiber will likely be found to modulate human colon cancer and the mechanisms of its beneficial effect will probably be through multiple actions within the lumen and at the level of the target tissue. Based on our current knowledge of the pathogenesis of colon cancer we cannot make definitive statements about what percentage of colon cancer might be prevented by a specific type or amount of dietary fiber but it is reasonable to conclude that consumption of fiber-rich diets is associated with reduced risk of colon cancer. It is quite plausible that the combination of dietary fiber, or its metabolites, in conjunction with other phytochemicals may be necessary to realize inhibition of the tumorigenic process.