Fact or Fiction: Can Exercise prevent Cancer?
Most people realize that exercise is important. It helps us stay mobile, maintain a healthy weight, and release physical and mental stress. Can it also help prevent cancer? The research is somewhat conflicting but there are numerous clinical trials showing that exercise may help reduce the risk of developing certain cancers.
According to the National Cancer Institute [1], observational studies have shown that exercise can lower the risk for the development of several common cancers including breast and colon cancer which are the first and fourth most common types of cancer [2]. These same observational studies show a favorable result when looking at lung cancer. However, the NCI did not conclusively determine if the increased physical activity was the causative factor or if smoking habits might be the bigger risk reduction component for that specific case.
How is exercise thought to help lower the risk of developing cancer? Well, there are actually several mechanisms thought to be at play. According to both the NCI [1] and Cancer Research UK [3] these include:
Maintaining a healthy weight -> Obesity is associated with an increased risk for numerous chronic health conditions (including cancer).
Reducing levels of insulin and sex hormones (including estrogen and growth factors) circulating in the blood -> These hormones can cause cancer cells to divide more rapidly and cause a quick progression in tumor growth.
Reducing inflammation -> Inflammation can promote faster replication of cells which is a key feature in the development of cancer.
Increasing immune system activity -> This causes the immune system to be better at recognizing and eradicating unusual types or numbers of cells in the body leading to fewer cancers.
Increasing transit time of food through the colon -> This means that there is less time for food (and potential cancer causing agents) to be in contact with the very sensitive lining of the gut. The gut’s cells also divide quite rapidly and can become damaged (leading to cancer) if someone is frequently constipated.
Reducing sedentary behaviors -> This goes without saying- routine exercise leaves less time for being sedentary. Sedentary behavior has been linked to obesity, poor circulation, blood clots, and other serious health conditions. One thing to note though is that even people who have a period of moderate or vigorous activity at one point in the day need to be mindful of how much sitting they are doing throughout the rest of the day.
Is exercise still a good idea after a cancer diagnosis has been made? The resounding answer is, of course! Studies have shown that exercise while receiving cancer treatments can:
Help improve mental health
Enhance physical functioning
Maintain or improve quality of life [1]
In a time when everything seems uncertain and downright terrifying, exercise can provide a distraction and remain constant in ever-shifting circumstances. Exercise has been shown to improve sleep and decrease adverse reactions due to cancer treatments such as lymphedema (swelling in the arm after breast cancer surgery) and neuropathy. [1] It has also been noted, specifically for breast, colon, and prostate cancer, that the risk of death due to the cancer is lessened by about 30-40%. [1]
It seems like there is a very strong case to be made for exercising after a cancer diagnosis and while receiving traditional cancer treatments. [4] The American College of Sports Medicine released guidelines five years ago detailing the importance and benefits of exercise at this critical time. The recommendations match the ones set forth by the American Cancer Society, American Heart Association, and the World Health Organization. [1] They have come to a consensus that the recommended weekly exercise goal should be 150-300 minutes of moderate exercise or 75-150 minutes of vigorous exercise. These recommendations also include regular strength training (weight-bearing exercises) and balance training for an overall well-rounded fitness regimen. [1]
Of course, increased physical exercise does show a benefit when thinking about cancer risk; however, as with all things in life when considering making positive lifestyle changes we should also consider other factors such as diet and the use of both legal and illegal substances. [1] Nevertheless, the importance of exercise is clear for both general good health and the prevention and treatment of cancer.
The previous research is not definitive as to the absolute benefit of exercise when evaluating cancer risk or survival after a cancer diagnosis. While several large randomized clinical trials are in progress, we will have to wait for those results to have a more conclusive answer.
Action Steps:
Develop and maintain a fitness routine
This should include at least 2.5 hours of moderate exercise or 1.25 hours of vigorous exercise per week.
In addition to aerobic exercise include weight-bearing exercises and balance training.
Keep it simple and enjoyable. Exercise can be as simple as walking on the treadmill or around your neighborhood.
Pick something YOU like. If you don’t like it then you won’t stick with it.
Minimize sitting or laying around as much as possible. No level of activity for one short period per day will minimize the negative effects of an overall sedentary lifestyle.
References:
Physical activity and cancer fact sheet - nci [Internet]. 2020 [cited 2024 Jun 24]. Available from: https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/physical-activity-fact-sheet
Common cancer types - nci [Internet]. 2015 [cited 2024 Jun 24]. Available from: https://www.cancer.gov/types/common-cancers
Cancer Research UK [Internet]. 2018 [cited 2024 Jun 24]. What are the benefits of exercise? Available from: https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/physical-activity-and-cancer/what-are-the-benefits-of-exercise
Prescribing exercise as cancer treatment - nci [Internet]. 2019 [cited 2024 Jun 24]. Available from: https://www.cancer.gov/news-events/cancer-currents-blog/2019/cancer-survivors-exercise-guidelines-schmitz
