They used to say that women who ingested high fat diets were more prone to breast cancer than women who had low fat diets. My own belief about that is that it wasn't the fat in their diets that caused the cancer, but the hormones in the meat and dairy products that they were eating. I have been told that the hormones my grandfather was given to fight his prostate cancer were responsible for giving him the breast cancer that killed him.

On the other hand, one of my parents' dogs got some kind of cancer or tumor on his mouth, and the vet said it was from his plastic food bowl.

I tend to think that there are all sorts of environmental causes of cancer, and possibly a few hereditary ones as well.