By Hope Cristol
You’ve heard for years that physical activity is important for your health. You may even know that exercise is important when it comes to cancer: It may lower cancer risk by helping control weight, reduce sex hormones or insulin, and strengthen the immune system; and it can boost quality of life during cancer treatment. Now, a new study from researchers at the American Cancer Society and the National Cancer Institute links exercise with a lower risk of 13 specific types of cancer.
That’s big news, because previous studies have investigated the link between physical activity and cancer risk, and results were inconclusive for most cancer types. The exceptions were colon, breast, and endometrial cancers. This new study, published May 16 in JAMA Internal Medicine, found that leisure-time physical activity was associated with a significantly decreased risk of not only these 3 cancers, but also esophageal cancer, liver cancer, stomach cancer, kidney cancer, and myeloid leukemia. In addition, physical activity was strongly associated with a decreased risk of multiple myeloma, a blood cancer, as well as cancers of the head and neck, rectum, bladder, and lung (in current and former smokers).
Study co-author Alpa Patel, PhD, strategic director of the Cancer Prevention Study-3 (CPS-3) at the American Cancer Society, weighs in on this and other findings from the analysis of self-reported physical activity among 1.44 million study participants.
The study explored the impact of “leisure time physical activity of a moderate to vigorous intensity.” What are some examples that most people with busy lives can reasonably attain?
You don’t have to be a marathon runner to consider yourself physically active. Walking at about 3 mph (or 20 minutes per mile) is considered moderate intensity. The American Cancer Society recommends that adults get at least 150 minutes of moderate intensity or 75 minutes of vigorous activity each week (or a combination of these). You can get in the recommended activity levels by just walking on your lunch break for 30 minutes, 5 days a week.
The study suggests that exercise is linked with lower cancer risk, regardless of body size. Why do you think this is?
One of the ways in which physical activity may lower risk of cancer is through weight maintenance. However, many other biologic processes are affected by physical activity that are independent of body weight. For example, physical activity is associated with lower estrogen and insulin levels, both of which may lower the risk of some types of cancer.
What surprised you about the findings?
We knew that a study this size would give us the statistical power to find new associations, but we didn’t expect risk reduction in so many cancers – some with more than a 20% lower risk. It was exciting to uncover an additional 10 types of cancer, besides colon, breast, and endometrial cancers, that may benefit from physical activity. It was also exciting to see that the results were broadly generalizable to people of all weights and regardless of smoking status (except for lung cancer).
What kind of impact do you hope this study has?
This study tremendously boosts the evidence base that physical activity may have an even more far-reaching benefit for cancer prevention. It adds support that health professionals should encourage all individuals to adopt a physically active lifestyle. My hope is that this study further motivates people to become active, whether going for a walk, swimming, riding a bike, jogging, or dancing. Find what you love to do and get active!