Colorectal Cancer Overview

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Causes, Risk Factors, and Prevention TOPICS

Can colorectal cancer be prevented?

Even though we don't know the exact cause of most colorectal cancers, it is possible to prevent many of them.

Screening tests

Screening is the process of looking for cancer in people who don't have any symptoms of the disease. Regular colorectal cancer screening is one of the best ways to help prevent colorectal cancer. Some polyps, or growths, can be found and removed before they have the chance to turn into cancer. Screening can also help find colorectal cancer early, when it is small and more likely to be cured. People who have no known risk factors (other than age) should begin screening at age 50. Those who have a family history or other risk factors for colorectal polyps or cancer (such as inflammatory bowel disease) should talk with their doctor about starting screening at a younger age or getting screened more often.

If you have a history of colorectal cancer in your family, you should talk with your doctor about when and how often to have screening tests.

Genetic testing, screening, and treatment for those with a strong family history

If you have a strong family history of colorectal polyps or cancer, you should think about getting genetic counseling to help you decide whether genetic testing or earlier screening may be right for you. Before getting genetic testing, it's good to know ahead of time what the results may or may not tell you about your risk. These tests are not perfect, and in some cases they may not be able to give you solid answers. This is why meeting with a cancer genetics expert before testing is a key part of choosing whether testing is right for you.

Diet, exercise, and body weight

Most studies have found that being overweight or obese increases the risk of colorectal cancer in both men and women, but the link seems to be stronger in men. Having more belly fat (that is, a larger waistline) has also been linked to colorectal cancer.

Overall, diets that are high in vegetables, fruits, and whole grains (and low in red and processed meats) have been linked with lower colorectal cancer risk, although it's not exactly clear which factors are important. Many studies have found a link between red meat or processed meat intake and a higher risk of colorectal cancer risk.

Studies show a lower risk of colorectal cancer and polyps with higher levels of activity. Moderate activity on a regular basis lowers the risk, but vigorous activity may have an even greater benefit.

In recent years, some large studies have suggested that fiber intake, especially from whole grains, may lower colorectal cancer risk. Research in this area is still under way.

Several studies have found a higher risk of colorectal cancer with increased alcohol intake, especially among men.

At this time, the best advice about diet and activity to perhaps reduce your risk of colorectal cancer is to:

  • Increase the intensity and amount of physical activity.
  • Limit intake of red and processed meats.
  • Get the recommended levels of calcium and vitamin D (see below).
  • Eat more vegetables and fruits.
  • Avoid obesity and weight gain around the midsection.
  • Avoid too much alcohol. Men should drink no more than 2 drinks a day, while women should limit themselves to one drink a day.

To find out more about diet and physical activity, refer to our document American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.

Vitamins and minerals

Studies looking to see if taking a vitamin or mineral supplement could help lower risk have not had clear results. Some studies suggested that taking a daily multi-vitamin that contained folic acid or folate could help lower colorectal cancer risk, but other studies did not. In fact, some studies have hinted that folic acid might help existing tumors grow. More research is needed in this area.

Some studies have suggested that vitamin D, which you can get from the sun, in certain foods, or in a vitamin pill, can lower colorectal cancer risk. Because of concerns that too much sun exposure can cause skin cancer, most experts do not recommend this as a way to lower colorectal cancer risk at this time.

Other studies suggest that getting more calcium may lower colorectal cancer risk. But because of the possible increased risk of prostate cancer in men with high calcium intake, the American Cancer Society does not recommend increasing calcium intake specifically to try to lower cancer risk.

Some studies found a link between a diet high in magnesium and lower colorectal cancer risk, with the strongest link in women. But not all studies have found this lowered risk. More research is needed on this subject.

Aspirin and other drugs

Aspirin and drugs like ibuprofen (Motrin®, Advil®) and naproxen (Aleve®) seem to lower the risk of colorectal cancer and polyps. But these medicines can have serious or even life-threatening side effects such as stomach bleeding. For this reason, experts do not advise the general public to take them to try to prevent colorectal cancer. If you are at high risk for colorectal cancer, talk to your doctor about what you should do.

Female hormones

Taking estrogen and progesterone after menopause (sometimes called menopausal hormone therapy or combined hormone replacement therapy) may reduce the risk of colorectal cancer in women after menopause. But cancers found in women taking these hormones after menopause may be at a more advanced stage. While taking these hormones after menopause lowers the risk of developing osteoporosis (bone thinning), it can also increase a woman's risk of heart disease, blood clots, and cancers of the breast and lung.

The decision to use hormones should be based on a careful talk about the benefits and risks with your doctor.

Some studies have found that the use of birth control pills may lower the risk of colorectal cancer in women. More research is needed to confirm this link.

Last Medical Review: 08/15/2013
Last Revised: 01/31/2014