Colon cancer is the third most common type of cancer diagnosed in American men and women, and sadly it will lead to more than 50,000 deaths in 2010 alone, based on National Cancer Institute estimates. However, despite being one of the most deadly forms of cancer, colon cancer is also one of the most preventable.
Background
Colon cancer occurs when one or more cancerous tumors grow from the wall of your large intestine, or colon. While colon cancer does run in families, indicating that genetics are at work, the National Cancer Institute states that approximately 75 percent of people diagnosed with colon cancer have not inherited genetic risk factors for the disease. This means that lifestyle factors like diet and exercise play an important role in colon cancer development. According to a study sponsored by the World Health Organization, at least 16 percent of colon cancer cases diagnosed around the world can be linked to a lack of exercise.
Prevention
A group of U.S. researchers compiled and reviewed the results of 52 different studies that investigated the effects of exercise on colon cancer development in a paper published in the "British Journal of Cancer" in 2009. They discovered through their analysis that the people who were the most active had a 24 percent lower chance of developing colon cancer than those who were the least active.
Improved Outcomes
Exercise may also be beneficial for people who have already been diagnosed with colon cancer. Two observational studies have shown that regular exercise following colon cancer diagnosis and treatment may help keep the cancer from coming back and protect you from dying. In these studies the risk of recurrence and mortality was reduced by up to half in people with early- to late-stage colon cancer that had not spread throughout their bodies, regardless of whether or not they had exercised regularly before their diagnosis.
Mode of Action
Experts aren't entirely sure why exercise, it seems, has such protective effects against colon cancer. One explanation is that exercise helps prevent a major cancer risk factor---obesity. However, reducing body weight may not be the only mechanism involved. A study published in "Cancer Epidemiology" showed that while exercise reduces the rapid cellular growth that leads to the development of colon polyps and cancer this effect was not linked to body weight. Exercise may also help prevent colon cancer by reducing inflammation, boosting the immune system, reducing blood glucose levels and reducing the time it takes for the colon to empty.
Recommendations
Current recommendations suggest that you do at least 30 minutes of moderate-intensity exercise on most days of the week, but more might be needed to reduce the risks associated with colon cancer. For example, a study published in the "Journal of Clinical Oncology" found that walking at a moderate pace for at least six hours a week was necessary to produce clear benefits for colon cancer patients. However, if you have never done regular physical activity before it is important to start out slowly and gradually build up the amount of time you exercise.Always talk to your doctor before starting any new exercise program to make sure you are healthy enough for physical activity.
References
- National Cancer Institute: Genetics of Colorectal Cancer.
- "Comparative Quantification of Health Risks"; Physical Inactivity; F.C. Bull, et al.; 2004
- "British Journal of Cancer"; Physical Activity and Colon Cancer Prevention: a Meta-analysis; K.Y. Wolin, et al; 2009
- "Journal of Clinical Oncology"; Impact of Physical Activity on Cancer Recurrence; J.A. Meyerhardt, et al.; 2006
- "Journal of Clinical Oncology"; Physical Activity & Survival after Colorectal Cancer; J.A. Meyerhardt, et al.; 2006
- "Cancer Epidemiol Biomarkers Prev"; Effect of a 12-month Exercise Intervention; A. McTiernan, et al.; 2006
