Is the changing pattern of colorectal cancer caused by selenium deficiency?

An hypothesis is presented to explain the changing pattern of colorectal cancer seen within the United States and other western countries in the last 30 years, the simultaneous increase of right-sided colonic cancer and disappearance of rectal cancer. Review of experimental and epidemiologic data suggests that this change may be due to a new systemic deficiency of the trace element, selenium. This deficiency has arisen not just from decreased consumption of selenium in the last 30 years, but also from increased consumption of zinc and fluoride, which may antagonize the effect of selenium.