The Impact of Exercise on Cancer Risk
Most of us know that physical activity, movement and exercise can help reduce our risk for heart disease, type 2 diabetes, dementia and other neurodegenerative diseases, depression and over-all risk of premature death. But, did you know that physical activity, movement and exercise can reduce your risk of developing many types of cancer. The converse is also true; sitting time has been correlated with an increased risk of some cancers.
Let’s look at what the current studies tell us.
In the United States there are 1.8 million new cancer diagnoses with an associated 606,000 deaths. Cancer is the second leading cause of death in the United States behind cardiovascular disease and it has been estimated that up to 60% of cancers are potentially preventable.
In the past 3 years there have been several large population studies looking at the link between physical activity and the risk for multiple different cancers. There is strong evidence that physical activity lowers the risk of the following cancers: breast, colon (particularly strong in men), kidney, endometrial (otherwise known as uterine), bladder, esophageal, liver and stomach. There is more limited but suggestive data that physical activity can also lower the risk of cancers of the lung, blood system, head and neck, pancreas and ovary. The magnitude of the risk reduction varied between 10 and 24%. It should be noted that this risk reduction did not depend on weight loss with the exception of uterine cancer.
Types of physical activity
There are several different types of physical activity including: leisure time activity (things such as running, cycling, swimming), occupational activity (manual labor), household activity (housework, gardening), active transportation (bicycling or walking to work) and walking. Although the data from the current studies focuses mainly leisure time physical activity it is thought that a broad range of any physical activity may be of benefit.
While the association between physical activity and cancer risk reduction is becoming more clear, the optimal dose remains elusive. The best evidence suggests that consistent, moderate (brisk walking) to vigorous (running, swimming or cycling at a fast pace) physical activity is most protective. The real key is that we get up and move as much as possible on a consistent, long-term basis. It appears that lifetime physical activity performed daily or at least 3 times per week has the most protective effect. Current recommendations are moderate exercise 5 days per week for 30 minutes each day. There is emerging evidence that more vigorous or more prolonged exercise may be more protective for certain cancers. The bottom line is to move, move and move some more as often as possible.
While exercise can reduce the risk of cancer there is emerging evidence that supports prolonged sitting time as a risk factor for cancer and that this is not reversed with adequate amounts of leisure time exercise. Prolonged sitting time has been correlated with increased death from all causes, increased cardiovascular disease and type 2 diabetes as well as an increased risk of some cancers. Several studies have shown that prolonged sitting times increase the risk of endometrial and colorectal cancer by 30% and lung cancer by 13%.
While the exact science of why exercise helps prevent cancer is unknown, there are some clues:
1)Cancer has been hypothesized to be mediated through three hormonal systems including sex steroids such as estrogen, insulin and insulin-like growth factors and adipokines (chemicals released by fat cells many of which cause inflammation). Exercise appears to reduce the levels of these pro-growth hormones thus lowering the risk of developing cancer.
2) Inflammation has tumor promoting properties and exercise has been shown to decrease inflammation.
3) Immune function is important in keeping cancer cells from growing and exercise helps boost immune function.
Starting an exercise plan?
If you want to start an exercise routine ask yourself these questions:
1) What type of physical activities do I enjoy?
2) What would you like to do if there was nothing holding you back?
3) What activities are difficult for you to do?
You should look for activities that match your affirmative answers. Physical activity should not only improve how you feel physically and emotionally but should also be fun and rewarding. Look for activities that benefit your daily life.
Some of you may say; “I am too busy to exercise”. If you think you are too busy look at making physical activity a priority. If you are watching TV every evening think about substituting this with some physical activity. Learn to incorporate physical activity into your daily routine. Take the stairs instead of the elevator. Park as far away from buildings as possible, walking that extra distance. Find some friends and go for a walk over the lunch hour. There are many creative ways to incorporate movement into your daily life. Use you imagination. Even small amounts of physical activity on a consistent daily basis can have large benefits over time. Something is better than nothing.
Physical activity is only one part of a cancer prevention lifestyle. Other preventative measures include a healthy diet avoiding all processed and fast foods as well as added sugars and focusing on a plant centered diet with 7-9 servings of vegetables and fruits daily, nurturing social connections and loving relationships, getting a restful 7-9 hours of sleep nightly and managing how you respond to stress through breathing and meditation practices.