You’ve heard for years that physical activity is important for your health. 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 of 1.44 million participants 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, said “We expected a study this size would give 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).”
You don’t have to be a marathon runner to consider yourself physically active. Walking at about 3 mph (or a 20-minute 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 achieve the recommended activity levels by walking on your lunch break for 30 minutes, 5 days a week. Physical activity is defined as any movement that uses skeletal muscles and requires more energy than does resting. It can include strenuous working conditions like construction, exercising, performing household chores that get the heart rate up, and leisure-time activities such as walking, tennis, hiking, bicycling, and swimming.
Changes in bloodstream following exercise may play a role in cancer prevention
Researchers found that in petri dishes which contained a tiny amount of fluid from the blood of 20 male colon cancer survivors who had just exercised, there were far fewer cancer cells than in those awash in fluid drawn from those who hadn’t exercised.
The researchers found a large increase in molecules involved in inflammation immediately after exercise. Inflammation can slow cell growth and reproduction. So a transitory increase in inflammatory markers after exercise might be helping to jam the proliferation of tumor cells, says Tina Skinner, a physiologist who was the senior author of the study. The implications of these results are both cheering and cautionary. The changes in exercisers’ blood were potent but transient. So activities would have to be repeated to provide any continuing protection, “We would recommend that exercise be embedded as part of standard practice for people living with and beyond cancer.”
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:
- Lowering the levels of hormones, such as insulin, and estrogen, and of certain growth factors that have been associated with cancer development and progression.
- Helping to prevent obesity and decreasing the harmful effects of obesity, particularly the development of insulin resistance (failure of the body’s cells to respond to insulin)
- Reducing inflammation
- Improving immune system functioning
- Altering the metabolism of bile acids, resulting in decreased exposure of the gastrointestinal tract to these suspected carcinogens
- Reducing the amount of time it takes for food to travel through the digestive system, which decreases gastrointestinal tract exposure to possible carcinogens
Clearly, exercise is imperative to keeping off the pounds and maintaining a healthy lifestyle, but now we know it can help prevent cancer as well. What further motivation do we need to become active? Whether it’s going for a walk, swimming, riding a bike, jogging, or dancing, find what you love to do and get active!