Cancer Cancer Basics

What Really Prevents Colon Cancer?

The effort to prevent colon cancer has suffered its share of recent setbacks. A diet high in fiber, while still key to a healthy digestive tract, appears to offer little protection against colon cancer, studies have now found. Meanwhile, calcium and vitamin D supplements are also in doubt, according to a major trial that tracked more than 36,000 women.

Low-fat diets are still considered healthy, but they lost some of their luster in the same major study, known as the Women's Health Initiative. Even exercise is being called into question.

Is there anything that can be done to prevent the second-leading cause of cancer death in the United States? Dr. Karen Emmons, a prevention expert at the Dana Farber Cancer Institute in Boston, says that the main risk factors for colon cancer have not changed because of the latest studies. A lack of exercise, being overweight, eating plenty of red meat, smoking, skimping on vegetables, drinking too much alcohol and not getting enough folate can all independently increase your chances for developing colon cancer. Changing these behaviors, it stands to reason, should offer some protection.

"Following a prudent diet and exercising can lower your risk of colon cancer and many other diseases as well," says Emmons.

But what about the latest research that seems to suggest otherwise? "Never draw conclusions on just one study," she says. The calcium and vitamin D study is a case in point. Out of the 18,000 women who received 1000 mg calcium and 400 IU Vitamin D a day, the risk of colon cancer after a period of seven years was about the same as an equal number of women who didn't take these supplements.

The women in the study, however, were at a lower risk of colon cancer to begin with, which may have made it hard to detect any positive effect from the supplements. Plus, this type of cancer can remain latent for 10 to 20 years, so following the women for a longer period may be necessary to show that calcium and vitamin D can indeed help.

"It's a matter of being patient as we figure out what works," says Emmons.

Indeed, while researchers have a clear understanding of what raises your risk for colon cancer, trying to prevent the disease is still open to debate. Experts had hoped that diets low in fat and high in fiber, fruits and vegetables would prevent colon cancer, but at least one well-designed study suggests that this fails to offer any real protection. As further research continues, Emmons says that at least one prevention method is a clear slam dunk.

"Screening for colon cancer is a great preventive opportunity," she says. By undergoing a colonoscopy every five years in men and women aged 50 years and older, or earlier if there is a history of colon cancer in your family, doctors can detect precancerous legions and remove them before they potentially become tumors.

"There's no question about that," says Emmons. "Screening works."