COLLEGE STATION, Texas (KXAN) – It has long been understood that exercise can be beneficial in preventing some types of cancers, but only in recent years have scientists started to understand why.

A team of Texas A&M researchers showed in a recently published paper that a hormone secreted by muscles during exercise can reduce tumor growth and even kill cancerous cells. 

“That was the cool and, I guess, groundbreaking news that we were able to show mechanistically – there is something released from skeletal muscle. When we put it on cancer cells, it slows the growth and sometimes kills them,” said Amanda Davis, a Clinical Assistant Professor at the School of Veterinary Medicine.

When skeletal muscles contract during exercise, hormones called myokines are released. This hormone goes into the bloodstream and can suppress the growth of those cancerous cells. 

Davis said they also investigated whether this phenomenon occurred in both long-time fitness enthusiasts and exercise newcomers. 

“And basically, there was no difference,” she said. “So that’s encouraging that you don’t need to be an Olympic level athlete to have the same benefit of exercise in potentially killing pre-neoplastic (abnormal) cells or it potentially [being used] as a treatment modality if you already have cancer,” she continued. 

Cancer is the second leading cause of death in the U.S., and breast cancer is the most common form for women. 264,000 women will yearly be diagnosed with the disease in the U.S., and 42,000 will die from it, researchers said.

The researchers looked at the effects of exercise on cancer cells found in the luminal A subtype of breast cancer – which accounts for around 70% of breast cancer cases. 

“We know that [exercise] could be beneficial in other cancers, but we haven’t proven it yet,” Davis said. “There are people who are extremely well in shape, and they get cancer – breast cancer, colon cancer,” Davis said. 

“That’s still something that needs to be pressed into and understood a little bit more…And then we can say, ‘Okay, this is how we can use exercise more specifically in preventing and treating these specific kinds of cancers,” she said.