Colon cancer is one of the most common types. Risk factors include a sedentary lifestyle, obesity, smoking, and overuse of alcohol. Studies of dietary changes have shown variable results. However, a recent review article from Germany describes good news on the exercise front: several studies demonstrate positive results from physical activity, independent of its effects on weight control.
In one study, the risk of colon cancer was reduced by 40 percent in men and women who exercised at least seven hours each week. The effect was just as strong for people who were previously sedentary as for those with a history of sports activity, so it's never too late to start. Other studies showed a reduction in incidence or mortality from colon cancer associated with exercise for at least 45 minutes, three times a week, or walking at least four hours per week.
The authors of the review article suggest three mechanisms for the benefits of exercise in these studies:
1.Insulin and insulin-like growth factor (IGF) are believed to influence the carcinogenesis process
2.Changes in the inflammatory response are associated with both exercise and carcinogenesis
3.Physical activity produces faster intestinal transit, and thus a shorter time for potential carcinogens to stay in contact with the intestinal walls
Cancer-related fatigue affects many patients who have already been diagnosed and treated. The symptoms include breathlessness, tachycardia (fast heartbeat), weakness, depressive mood, and a tendency to feel tired easily. These symptoms make exercise more difficult, but physical training can improve the fatigue symptoms as well as prevent recurrences of the cancer.
Both strength training and endurance (aerobic) exercise are recommended. The authors suggest working up to three to five units of training per week, 30 to 60 minutes long. Aerobic exercise can be performed every day, if desired, but strength training sessions should be spaced one to two days apart.
While weight loss is not the primary goal of exercise to prevent colon cancer, it may be a welcome side effect. The optimum body mass index is 18.5 to 24.9. A calculator is available online at http://www.nhlbisupport.com/bmi/. To find your current body mass index, just type your height and weight into the boxes on this site.
To calculate what weight would put you in the optimum range,
1.Get your height in inches, e.g. 5 feet 2 inches = 62 inches.
2.Square this number: height factor = (height in inches) x (height in inches)
3.Multiply 0.0354 times height factor. This is the maximum weight in pounds that will put you in the optimum range.
4.Multiply 0.0263 times height factor. This is the minimum weight in pounds for the optimum range.
Reference:
Halle M et al, “Physical activity in the prevention and treatment of colorectal carcinoma”, Dtsch Aztebl Int 2009; 106(44): 722-7.
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.