Updated May 24, 2015.
Staying active is something that often comes to mind as a way to avoid heart disease, but using exercise to prevent cancer may fall outside our health radar. The fact is, emerging research shows that regular physical activity is linked with significantly lower rates of a variety of cancers.
For example, the risk of breast cancer, colon and endometrial cancers drops by 25-30% in people who are physically active, according to a 2012 paper published in Chronic Diseases and Injuries in Canada.
The incidence of prostate, lung, ovarian and certain gastrointestinal cancers are also linked with physical activity. The authors suggest that positive effects of exercise on sex and metabolic hormone levels, insulin resistance and inflammation within the body may all play a role in preventing and slowing the progression of certain cancers.
Since exercise can help people maintain a healthy weight and avoid obesity (in particular dangerous belly or abdominal fat), it may help you avoid additional forms of cancer including those affecting the kidney and esophagus as well.
- Read more: Which cancers are obesity-related?
So how much is enough physical activity, to prevent cancer? In an effort to promote more physical activity for cancer prevention, a number of health agencies have produced exercise guidelines over the last few decades. Here's a look at what they recommend.
1. American Cancer Society: The American Cancer Society (ACS) has issued Nutrition and Physical Activity Cancer Prevention Guidelines which score adults according to four aspects of health and lifestyle habits, including physical activity, body weight, diet and alcohol consumption.
Tobacco smoking - widely known to increase lung cancer and mortality risk - is considered separately within the guidelines.
The ACS recommends at least 30 minutes or more of "moderate to vigorous" intentional physical activity at least 5 days a week, though it stipulates 45-60 minutes daily are preferable to reduce cancer risk.
2. US Department of Health and Human Services (USDHHS): USDHHS recommends a minimum of 150 minutes of moderate to vigorous physical activity each week, or an average of just more than 20 minutes each day.
3. World Cancer Research Fund International (WCRF): This international agency estimates that along with following a nutritious diet and maintaining a healthy weight, regular physical activity can help prevent about a third of the most common cancers.
The WCRF recommends moderate physical activity (such as brisk walking), for at least 30 minutes each day. It also advises boosting daily activity to either 60 minutes or more of moderate exercise, or at least 30 minutes of vigorous physical activity daily as fitness levels improve - and to limit the time spent sitting each day.
What difference does the higher activity level really make? The good news is that being more active does seem to help prevent cancer. A 2014 study of more than 65,000 post-menopausal female subjects participating in the Women's Health Initiative revealed that those who scored highest on the American Cancer Society's Cancer Prevention Guidelines had a 17% lower risk of any form of cancer (and 20% lower risk of cancer-related death) when compared with those scoring lowest on the ACS scale.
Unfortunately, adherence remains a problem for many would-be exercisers. The 2012 study out of Alberta, Canada revealed that only 42% of men and women between the ages of 35-64 years adhered to the ACS guidelines of 30 minutes of activity, 5 days a week. The same study showed that just 23% followed the more stringent WCRF recommendation of 60 minutes (moderate) or 30 minutes (vigorous) daily exercise.
Time the major obstacle to getting enough exercise: If you're looking in dismay at the time commitment required to log enough cancer-fighting physical activity, you're not alone. Surveys have shown that a lack of time is the number one reason we don't exercise regularly. Feeling too tired or weak, not having access to a gym and not being supported in the activity by family or friends are also blamed as stumbling blocks to daily exercise.
Try getting more activity throughout your entire day: If you're struggling with working activity into your day, one solution is to look not just at your shrinking leisure hours (or minutes, depending how busy you feel!) for formal exercise like going to the gym. The other portions of our lives - in which we are at work, in transit during the day, and at home - offer many opportunities to be on the move. It all adds up, whether you're able to go part of the way to your office on foot, hold walking meetings with colleagues, stand while talking on the phone, or even vigorous housework or gardening.
While cancer risk is influenced by our genetics, the American Cancer Society stresses that taking steps within our control to stay at a healthy weight, eating a varied and nutritious diet, avoiding tobacco and remaining active will greatly reduce that risk. Long-term studies back this up, showing that disability and chronic diseases including cancer are reduced with fairly simple lifestyle habits. The trick is daily, consistent effort: not easy, but worth it in the years to come.
Sources:
Aparicio-Ting FE1, Friedenreich CM, Kopciuk KA, Plotnikoff RC, Bryant HE. "Prevalence of Meeting Physical Activity Guidelines for Cancer Prevention in Alberta." Chronic Dis Inj Can. 2012 Sep;32(4):216-26.
http://www.phac-aspc.gc.ca/publicat/hpcdp-pspmc/32-4/ar-06-eng.php
Thomson CA1, McCullough ML, Wertheim BC, Chlebowski RT, Martinez ME, Stefanick ML, Rohan TE, Manson JE, Tindle HA, Ockene J, Vitolins MZ, Wactawski-Wende J, Sarto GE, Lane DS, Neuhouser ML. "Nutrition and Physical Activity Cancer Prevention Guidelines, Cancer Risk, and Mortality in the Women's Health Initiative. Cancer Prev Res (Phila). 2014 Jan;7(1):42-53. doi: 10.1158/1940-6207.CAPR-13-0258
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4090781/
Physical Activity Recommendations. World Cancer Research Fund International Public Information Sheet. Accessed May 9, 2015.
http://www.wcrf.org/int/research-we-fund/our-cancer-prevention-recommendations/physical-activity