Move It to Stave Off Cancer

Exercise good for your mental health, physical strength and stamina. And it can help you prevent cancer

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Many things that cause cancer are not under our control. These include genetics, family history and early environmental exposures. That’s the bad news.

But the good news is that current research has identified a number of factors in the development of many types of cancer that are under our control. Modify these and we may mitigate risk. There are a few big ones: we can avoid too much sun exposure, quit smoking, eat better and become more physically active. It’s the last one, physical activity, that many people find surprising.

WHAT DOES THE RESEARCH SAY?
Dr. Christine Friedenreich, an epidemiologist in cancer care at Alberta Health Services, is a world expert on the associations between exercise and cancer prevention. She conducted a number of studies looking at large groups of women with breast cancer. She has since expanded her studies to include a wide variety of cancers to try to identify differences between people who went on to develop cancer and those who stayed healthy. In fact, a very large body of research on the relationship between exercise and cancer has accumulated, with hundreds of studies looking at hundreds of thousands of people all around the world.

Recently Dr. Friedenreich reviewed all these papers in the European Journal of Cancer (2010) and concluded that overall, physical activity decreases the risk for cancers by about 25 per cent. That means that one in four cancers could have been prevented by increasing levels of physical activity alone. The types of cancers that have the strongest research support for this association are colon, breast, endometrial (uterine), lung, prostate and possibly ovarian. Other types of cancer have not been studied enough to conclusively say whether physical activity would help or not, but it is likely that this effect translates across most cancer types. The authors estimated that in Europe, if people exercised more, as many as 330,000 new cases of cancer could have been prevented in 2008 alone.

HOW MUCH EXERCISE IS ENOUGH?
The recommendations based on this large body of research say that people should do 30 to 60 minutes of moderate or vigorous activity at least five days a week. Moderate activity includes walking briskly, gardening, cycling or dancing, but can also include household or occupational tasks such as scrubbing, mopping, vacuuming, hammering or lifting and carrying heavy objects such as building materials or even groceries. More vigorous activities include anything that makes you breathe hard, such as running, swimming laps, playing sports such as soccer or hockey, climbing stairs or biking up hills.

HOW DOES PHYSICAL ACTIVITY PREVENT CANCER?
Many studies are underway looking at several possible reasons for this effect. The best understood mechanisms behind exercise’s impact in reducing cancer across groups relate to the beneficial effects of lowering body fat and increasing muscle mass. Less fat on your body results in lower levels of some hormones related to cancers, including estrogens and testosterone. Lower body fat also improves insulin sensitivity and resistance and decreases markers of inflammation. Improved lung function as a result of physical activity may also lower concentrations of cancer-causing materials in the lungs. All of these biomarkers are known to be risk factors for various forms of cancer.

WHEN IS IT TOO LATE?
The good news is it’s never too late. In fact, research shows that the biggest effect of exercise on prevention of breast cancer occurs in women over the age of 50. So whatever you enjoy doing, get out there and do more of it. There are plenty of resources out there that encourage inactive people to incorporate more physical activity. Not only is exercise good for your mental health and physical strength and stamina, we now know it can also help to prevent cancer.

Dr. Linda Carlson (lindacarlson.ca) is the Enbridge Chair in Psychosocial Oncology at the Tom Baker Cancer Centre and a clinical psychologist at the University of Calgary.

4 Responses to Move It to Stave Off Cancer

  1. John Peck says:

    Nice to hear. When’s the greatest benefit for men?

  2. Christine Friedenreich says:

    Maintaining regular physical activity throughout life provides the most benefit in reducing the risk of cancer in both men and women. However, there is also a benefit if regular activity is started later in life even if someone has been inactive previously. Physical activity clearly reduces the risk of colon cancer and possibly also of prostate cancers and other cancers that affect men as well as women. The main take home message is to try to be as physically active as you can and to maintain that activity throughout your life.

  3. Patricia says:

    what statistics are there concerning prevention of relapse/progression in existing/remissive caners?

  4. Christine Friedenreich says:

    There have now been 27 studies published worldwide that have examined how physical activity done either before or after cancer can improve survival after cancer diagnosis as well as decrease the chance of a recurrence, progression or a new primary. These studies have been conducted primarily in breast cancer (17 studies), colon cancer (6 studies) and prostate (1 study), glioma (1 study) and ovarian cancer (2 studies). Overall, these studies are finding that the risk of death after these cancers (cancer-specific death as well as overall mortality) is reduced by about 30% amongst the participants who are the most physically active compared to the least active. Hence, although the research is still emerging and preliminary for many cancer sites, the results are promising and suggest that being physically active after cancer can improve survival. Several on-going randomized controlled trials are examining specifically how much exercise and what type of exercise needs to be done to improve physical and mental well-being after cancer. No trials have yet been completed that have examined how exercise improves survival. However, one trial is currently on-going in Canada and Australia that is led by researchers here in Alberta that is examining how a three year long exercise program will improve survival in colon cancer survivors who have completed their treatments. That study will follow 962 colon cancer patients for 10 years to determine what the benefit of the exercise program was on their survival. For now, the best advice for cancer patients is to try to incorporate as much activity as possible during and after completion of treatment for cancer and to seek advice from a certified exercise physiologist with training in working with cancer survivors when setting up such an exercise program.

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