5. A diet high in fat, low in nutrients

If a person's diet has been heavy on red meat and low on vegetables and whole grains, this increases his risk of colorectal cancer. A diet high in animal fat has been linked with colon cancer, as has a diet low in calcium and folate. Eating at least five daily servings of fruits and vegetables protects against colon cancer.

6. Alcohol consumption

Drinking more than two alcoholic drinks a day has been linked to colorectal cancer. Drinking three or more alcoholic drinks a day substantially increases the risk.

7. Being African American

African Americans have the highest incidence of colorectal cancer, and whites come in second. Asians have a significantly lower incidence, and Hispanics and Native Americans are lowest of all, with close to half the incidence of colorectal cancer compared with whites and African Americans.

8. Genetic history

Between 3 and 5 percent of colorectal cancers are caused by an inherited genetic susceptibility to the disease; the most common of these is Lynch syndrome, or HNPCC (hereditary nonpolyposis colorectal cancer). A genetic mutation most common in people of Eastern European Jewish descent (also called Ashkenazi Jews) is also responsible for an increased risk of colon cancer.