Exercise reduces the chance of developing cancer by seven percent, according to a new study.
The massive study, which involved over 1.4 million people, was done by researchers at the National Cancer Institute and published in the JAMA Internal Medicine.
Researchers found that exercise lowered the risk of developing esophageal cancer by 42 percent. Exercise lowered the risk of liver cancer by 27 percent, lung cancer by 26 percent, by 20 percent for a specific type of leukemia and finally, by 10 percent for breast cancer.
The study says exercise may lower the risk for 13 types of cancer.
The study adds to the already long list of health benefits as a result of exercise.
Exercise "can help people reduce their risk of heart disease. It can reduce the risk of diabetes. It extends life expectancy. And now it appears that it may reduce the risks of some cancers," said Steven Moore of the National Cancer Institute, who led the study, in an interview with NBC News. "... these associations are broadly generalizable to different populations, including people who are overweight or obese, or those with a history of smoking."
The study looked at participants in 12 U.S. and European groups who reported on their physical activity between 1987 and 2004. The researchers looked at the occurrence of 26 kinds of cancer among the participants during, on average, the next 11 years.
Walking, running and swimming were commonly reported activities, and researchers also took into account the amount of each exercise in minutes per week.
Researchers also controlled for other risks of cancer like smoking and obesity, but researchers did add that diet could also have affected the results.
Exercise was beneficial to overweight participants, the researchers noted.
Moore told NBC that there are three possible explanations for the findings. First, exercise can lower hormone levels like estrogen, which would lower the risk of breast and endometrial cancers.
He said exercise helps maintain insulin and may lower overall inflammation in the body.
Researchers found that exercise increased the chance of developing prostate cancer by five percent.
"There is no known biological rationale to explain this association," the researchers wrote.
Heavier exercisers also had a slightly higher incidence of skin cancer, perhaps as result of more sun exposure.
