Colon cancer is the third leading cause of death worldwide. It is caused by a number of genetic changes over time and while it can be hereditary, it is largely based on diet and lifestyle. The role of fiber in colorectal cancer has been largely debated due to numerous studies with varying results. A recent study in Cancer Discovery provides strong evidence that dietary fiber does in fact protect against colon cancer.

Scientists took mice that were bred to have no bacteria in their guts, called gnotobiotic mice, and colonized them with Butyrivibrio fibrosolvens, a bacterium that produces butyrate. The mice were then exposed to either a high or low-fiber diet. The mice that were fed a high-fiber diet were protected against colorectal carcinoma. However, mice exposed to a high fiber diet that were not colonized by B. fibrosolvens were not protected against the carcinoma, telling us that the microbiome of the mouse as well as the high-fiber diet resulted in this protection and not the fiber alone.

Several epidemiological studies over time have failed to show a connection between fiber intake and colon cancer. This study suggests that this may be due to the studies’ failure to control for the study participants’ microbiomes. High fiber alone does not protect against colon cancer but in conjunction with a microbiome that produces high levels of butyrate, they may be protected from colorectal carcinoma. The authors of this study suggested that past studies should be revisited to look at differences in the microbiomes of participants. It will be interesting to see what findings are made as a result of this discovery and if in fact epidemiological studies are done to control for the microbiome.