Physical activity lowers risk of 13 cancer types

Once again, exercise continues to prove to be a valuable asset in keeping us healthy.   A huge study of 1.44 million participants from the United States and Europe ranging in age from 19-98 showed an association of leisure-time physical activity lowering the risks of 13 different types of cancer.  The May 2016 featured in JAMA Internal Medicine, emphasized that most of the associations were evident regardless of body size or smoking history.

It has been known for a long time from previous studies that being physically active can help reduce the risk of colon, breast, and endometrial cancers.  What was not conclusive was whether increased exercise was considered a strong predictor of reducing risk of other types of cancer due to small numbers of participants in past studies. 

The objective of the study was to determine what cancers were associated with leisure time physical activity and whether associations varied by excess body-weight and smoking.  A total of 26 different types of cancers were looked at in this study.  Participants were followed for a median of 11 years during which 187,000 new cases of cancer occurred.  Because of the high number of study participants, it is believed to be the largest ever conducted on physical activity and cancer risk.

What was found was that those who were physically active the most had an overall lower risk of the following 13 different types of cancers:

·         A 42 percent lower risk of esophageal cancer

·         A 27 percent lower risk of liver cancer

·         A 26 percent lower risk of lung cancer

·         A 23 percent lower risk of kidney cancer

·         A 22 percent lower risk of stomach cancer

·         A 21 percent lower risk of endometrial cancer

·         A 20 percent lower risk of myeloid leukemia

·         A 17 percent lower risk of myeloma

·         A 16 percent lower risk of colon cancer

·         A 15 percent lower risk of head and neck cancer

·         A 13 percent lower risk of rectal cancer

·         A 13 percent lower risk of bladder cancer

·         A 10 percent lower risk of breast cancer

The study revealed that when they compared people who exercised more than 90 percent of everyone else in the study, they had lower rates of cancer. The participants filled out self-reported surveys of their leisure time physical activity.  Participants exercised on average about two and a half hours of moderate exercise like walking each week.  Those who had a higher level of leisure-time physical activity had a 7 percent lower risk of total cancer.  What also was interesting was that even though obesity is a known risk factor for some types of cancer, obese participants who exercised had less cancer risk.  This can be encouraging news for anyone overweight to obese to keep active.

Why does exercise appear to have such a strong role in helping reduce the incidence of many different types of cancer?  There are several theories the researchers hypothesized as to the answer to this.  One is we know exercise has many benefits.  It reduces heart disease, the risk of diabetes, extends life expectancy and reduces obesity. 

Secondly, exercise may lower cancer by directly affecting the growth of new tumors.  Exercise lowers levels of the hormone estrogen decreasing the risk of breast and endometrial cancers.  Exercise uses up excess blood glucose helping to better regulate insulin and exercise appears to lower inflammation. 

This study creates a strong link of physical activity tied to lowering cancer risk in a wide age range.  It appears to prove the relevancy of physical activity in its capacity to have a far reaching role in preventing many different types of cancer.