Researchers at Washington University School of Medicine in St. Louis and Harvard University combined and analyzed data of past studies on the effect of exercise on colon cancer risk. They found that people who exercised were 24 percent less likely to develop colon cancer than people who exercised the least.
Kathleen Y. Wolin, Sc.D., and her colleagues analyzed 52 studies dating back to 1984 and found that the protective effect of exercise was consistent, whether the activity was recreational or occupational. (1)
In May 2005, at the annual meeting of the American Society of Clinical Oncology, Jeffrey A. Meyerhardt, M.D. MPH, presented the first study to demonstrate the benefit of exercise in patients who already had colon cancer. Patients involved in this study reported leisure-time physical activity approximately 12 to 18 months after surgery.
The health benefits of exercise were found among patients who exercised at a rate of at least 18 metabolic equivalents of task (MET) per week. A person's risk of having a reoccurrence or dying was lowered by 40 to 50 percent in the 2 and 1/3 to 3 years following surgery and chemotherapy for stage 3 colon cancer. (2)
MET is a ratio comparing a person's metabolic rate at rest to metabolic rate while performing a task. Fitness levels range from 1.5 MET for the lowest exercise capacity to 20 MET for the highest capacity. The average fitness level is 8 MET. (3)
In the most recent issue of Archives of Internal Medicine, Dr. Meyerhardt and his fellow researchers from the Dana-Farber Cancer Institute present the results of a large cohort study which examined the benefits of exercise on colorectal mortality. The team looked at the colorectal cancer-specific and overall mortality rates of 668 men who had a history of stage 1 to stage 3 colorectal cancers, and no evidence of metastases at the time of diagnosis.
Men who died within six months of their post diagnosis physical assessment were excluded from the final analysis. More than 50 percent of the men exercised the equivalent of one hour of walking at least six days per week. Researchers found that patients who engaged in moderate physical activity were 53 percent more likely to be alive and free of the disease.
Age, disease stage, body mass index, diagnosis year, tumor location, and physical activity before diagnosis did not appear to affect the benefit of physical activity. (4) "However, while our work found a significant benefit for patients who exercise, it's important that exercise still be seen as a supplement to, not a replacement for, standard therapies," concludes Dr. Meyerhardt.
(1) Physical Activity and Colon Cancer Prevention: a meta-analysis, Kathleen Y. Wolin, Sc.D et al
British Journal of Cancer 2009
(2) www.sciencedaily.com
(3) www.americanheart.org
(4) Physical Activity and Male Colorectal Survival Jeffrey A. Meyerhardt, M.D. MPH et al
Archives of Internal Medicine vol. 169 no. 22 December 14/28, 2009