Fiber exerts a protective role in colon cancer through two mechanisms:
Direct mechanisms: Fiber decreases the exposure time of the cells that form the colon wall to substances with carcinogenic potential, due to decreased intestinal transit time and, in part, to the adsorption and dilution of these substances in the colon. gel that forms the fiber. In addition, fiber increases the excretion of bile acids in the feces.
Indirect mechanisms: In the fermentation process of the fiber in the colon, substances such as butyric acid are produced, which could slow down the development of the tumor. In addition, the fermentation of the fiber by the bacteria of the colon lowers the pH to that level, being able to stop the development of cancer or a precancerous lesion.
However, it is not easy to establish a cause and effect relationship between dietary factors and colon cancer. Many experimental studies provide evidence supporting the protective effect of dietary fiber against colon cancer. Likewise, there are numerous epidemiological studies that have reinforced this relationship. However, recent clinical studies have not confirmed that a high-fiber diet reduces the incidence of colon cancer. Perhaps we should consider, so that cancer can appear, not only a low fiber intake, but also an intake rich in animal fats, which would act as an enhancer.
But, although the currently available evidence cannot unequivocally attribute the protective role of fiber consumption against colon cancer, there is a general scientific consensus on recommending a diet rich in fiber (vegetables and fruits), without forgetting the importance in the modification of other dietary factors and lifestyles that may be involved in an increased risk of this cancer.