Can exercise prevent cancer?

Medical research is well known to have proven that exercise can improve health by reducing  our risk of premature death and death from heart disease.  Exercise decreases  rates of hypertension, diabetes, osteoporosis and arthritis and can improve our sense of psychological well being . What is less widely appreciated is the compelling evidence that exercise can PREVENT some kinds of cancer.

Is this really a big deal?
The most compelling evidence relates to the reduced risk of developing colon cancer. More than 50 different studies have consistently demonstrated that adults who increase  the intensity, frequency or duration of exercise can reduce their risk of developing colon cancer by 30-40% relative to those who are sedentary.  According to the American Cancer Society, the lifetime risk of developing colon cancer is about 1 in 20. A 35% reduction in that risk would change the numbers to only 1 in 30. Studies in breast cancer risk reduction (more than 60 so far) are more variable but show 20-80% risk reductions.  Current US estimates place a woman’s lifetime risk of developing  breast cancer at 1 in 8.  If we assume a conservative 30% benefit, this would change the odds to 1 in 18!   There are fewer studies but positive results for lung cancer, endometrial cancer, and prostate cancer as well.

How does it work?
Researchers don’t think that people who exercise are just more heath conscious. It seems that exercise changes the way our bodies work and the way our genetic material is expressed or emphasized. Exercise induces changes in hormone metabolism, insulin regulation, and changes the genetic expression of growth factors and immune modulators.  The impact of these specific changes on cancer is the subject of ongoing research.

How much exercise is enough?
The studies differ widely in the subject’s frequency, duration and intensity of exercise, so making comparisons is difficult. In some studies more vigorous activity seemed most  helpful, and in breast cancer research activity in adolescence seemed particularly helpful, but changes in exercise even after menopause still produced benefits. Exercise helped across all ages, and across all body types as measured by body mass index.  It is generally accepted that  30- 60 minutes of moderate to high intensity of physical activity is sufficient to achieve cancer risk reduction.  Examples of moderate and vigorous exercise can be found here. If you have questions about your own risk of cancer, cancer screening, or would like to discuss exercise capacity and goals we would be glad to help!