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Physicians recommend that colon-cancer screening begin at age 50, but there are things you can do now to help prevent colon cancer. Talk with your physician and tell others to be screened.

The incidence of colon cancer increases with age. Nine of 10 colon-cancer diagnoses are in people over the age of 50. This is why doctors recommend that colon-cancer screening begin at age 50 for most people.

However, a history of colon cancer in your family may mean you need to begin screening earlier.

Most colorectal cancers occur in people without a family history of colorectal cancer. However, up to 20 percent of people who develop colorectal cancer have other family members who have been affected by the disease.

Those with a history of colorectal cancer or adenomatous polyps in one or more first-degree relatives (parents, siblings, children) are at an increased risk. The risk is about doubled in those with a single affected first-degree relative and even higher in those with a strong family history such as a first-degree relative diagnosed with colorectal cancer or adenomatous polyps before age 60, or two or more first-degree relatives with a diagnosis of colorectal cancer or adenomatous polyps.

The reasons for the increased risk are not clear in all cases. Cancers can "run in families" because of inherited genes, shared environmental factors or some combination of these.

People diagnosed with adenomatous polyps or colorectal cancer should inform another family members. Doctors generally recommend that individuals with a family history should begin screening at age 40 or 10 years before the youngest case in the immediate family, whichever is earlier.

If you have had colorectal cancer, even though it has been completely removed, you are more likely to develop new cancers in other areas of the colon or rectum. The chances of this happening are greater if you had your first colorectal cancer before the age of 60.

Women with a history of cancer of the breast, ovarian or endometrium also face an increased risk of developing colorectal cancer.

If you have a history of adenomatous polyps you are at an increased risk of developing colorectal cancer. This is especially true if the polyps were large or if there were many of them.

If you have inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease, you face an increased risk of colorectal cancer and you need to be screened on a more frequent basis.

Long-term smokers are more likely than non-smokers to develop and die from colorectal cancer. While smoking is a well-known cause of lung cancer, some of the cancer-causing substances are swallowed and can cause digestive cancers such as colorectal cancer.

A diet that is high in red meats and processed meats can increase colorectal-cancer risk. Methods of cooking meats at very high temperatures create chemicals that might increase cancer risk, although it is not clear how much this might contribute to colorectal cancer.

Diets high in vegetables and fruits have been linked with decreased risk of colorectal cancer. Whether other dietary components (fiber, certain types of fat, etc.) affect colorectal cancer risk is not clear.

If you are not physically active, you have a greater chance of developing colorectal cancer. Increasing your activity may help reduce your risk. Experts recommend that individuals engage in moderate physical activity for at least 30 minutes a day, for five or more days per week. For example, one Hutchinson Center study found that regular, moderate-to-vigorous aerobic exercise significantly reduces a risk factor associated with the formation of colon polyps and colon cancer in men.

About 5 percent of people who develop colorectal cancer have an inherited genetic susceptibility to the disease. The two most common inherited syndromes linked with colorectal cancers are familial adenomatous polyposis and hereditary non-polyposis colorectal cancer.

People with adenomatous polyposis typically develop hundreds or thousands of polyps in their colon and rectum, usually in their teens or early adulthood. Cancer usually develops in one or more of these polyps as early as age 30. By age 40, almost all people with this disorder will have developed cancer if preventive surgery (removal of the colon) is not done.

Hereditary non-polyposis colon cancer also develops when people are relatively young. People with this disease have polyps, but they only have a few. The lifetime risk of colorectal cancer in people with this condition may be as high as 70 percent to 80 percent.

Physicians recommend that colon-cancer screening begin at age 50, but there are things you can do now to help prevent colon cancer. Talk with your physician and tell others to be screened.

Please consult with your physician about your risk factors and the need for colon-cancer screening. Learn more about colon-cancer screening and prevention.