This is from 1984.

Colorectal Cancer And Bowel Habits, Cancer, October 1984

There two major hypotheses regarding the etiology [cause] of colorectal cancer.

The first is that long-chain fatty acids, present in dietary fat or endogenous bile acids, are converted to carcinogens or cocarcinogens by the action of gut bacteria.

The second hypothesis, which is complementary to the first, is that a high-fiber diet accelerates material through the gut and increases its bulk, thereby reducing both the amount of time bowel flora have to produce carcinogens and the amount of time these carcinogens have to act upon the gut wall, as well as reducing their concentration.

Putting aside the content of these statements for a moment, I was struck, in a good way, by how this was framed. Outcomes are the result of many factors acting together. It’s an equation. When it comes to chronic illness, it’s too simplistic to say that “this” causes “that”.

If you look very closely at just one variable, you may find no association, e.g. you may find no association between transit time (the speed at which food moves through the colon) and colon cancer, or you may find no association between dietary fat and colon cancer. But taken together (along with other variables, not least of which an immune response) these inputs may indeed contribute to a particular output, in this case colon cancer.

On a related note … Did you know that having a bowel movement every day does not, by itself, indicate that food is moving through the colon quickly? I’ll address Burkett’s study in my next post.

However, Burkett and associates found that feces may remain in the bowel for several days, yet be associated with a daily bowel movement; thus bowel movements may not reflect transit times with complete accuracy.