The Medical Minute: Connections between exercise and cancer

September 17, 2003

By John Messmer, M.D.
Penn State Milton S. Hershey Medical Center

Everyone knows that exercise has many benefits. Exercise improves fitness levels giving us more energy for daily activities. It makes our hearts stronger and reduces our risk of heart attacks and strokes. Most people understand that exercise also can help to prevent or control diabetes and improve cholesterol levels. Exercise helps lower blood pressure and can even help arthritis and reduce depression. But did you know exercise can reduce the risk of cancer?

A study published this month in the Journal of the American Medical Association looked at a large group of women in the Women's Health Initiative comparing exercise levels at various times in their lives. The researchers found that those who exercised by walking briskly for 30 minutes five times a week has a significant reduction in their risk of breast cancer. There was a bit more benefit from longer exercise. Lower body weight increases the benefit. Several previous studies have also shown a reduction in breast cancer risk with exercise.

But the benefits don't stop with breast cancer. Regular exercise reduces ovarian cancer risk, which is good news because ovarian cancer is difficult to detect. It has long been recognized that exercise lowers the risk of uterine cancer. Women aren't the only ones to benefit -- lung cancer risk can be cut by as much as 40 percent by regular exercise. Even colon cancer risk is lower by about 50 percent with regular exercise. In the lab, prostate cancer cells appear to be inhibited by regular exercise.

To achieve these risk reductions, the exercise must be regular and last a half hour. Unfortunately, a pick up game of basketball on the weekend or a bike ride on a sunny Saturday afternoon once in a while won't help. To be beneficial, exercise sessions must be 30-minutes long. There is some controversy whether three 10-minute segments are as good as one 30-minute session but probably the benefit is similar. Exercise should be four or five days a week so that your weekly total is about two and one-half hours.

Researchers are investigating why exercise has this salutary effect. Weight loss also helps reduce cancer risk by changing hormone levels that can influence cancer growth, but the benefit seems to be due to more than weight loss. Part of the reason may be that the immune system cells that fight cancer work better in people who exercise.

You don't have to be an athlete to get a reduction in cancer risk. Vigorous walking is enough although benefits are greater and energy levels are higher with more intense exercise. Exercise helps with weight loss, but you must also follow a reduced calorie diet if you want to take off pounds.

When you think about it, exercise is really amazing. If it were offered in an infomercial, you'd probably buy it -- it's all natural, inexpensive, does not require a prescription and can be used by everyone. It makes you stronger, gives you more energy, and prevents disease and cancer. You don't need your credit card, no operators are standing by -- just get up and get going to better health.

(Media Contacts)

Last Updated March 19, 2009