The big news in cancer treatment these days is a new kind of high-tech immunotherapy that unleashes the body’s own ability to target and kill tumor cells.

But new research has found that there may be something very similar that goes on in your body—any day you exercise a certain way.

Scientists had previously understood, in a general way, that exercise helps prevent cancer and helps prevent the recurrence of cancer.

But now, thanks to new research, we understand better how to unleash that exercise-based tumor-fighting response in a way that may both prevent and treat cancer. The research involved mice, but those results often transfer to humans. Here’s what was discovered…


In a series of experiments, researchers trained one set of mice to run on treadmills while another group was more sedentary. They then injected the mice with tumor-producing carcinogens.

The exercising mice fought the tumors better. They had fewer tumors, and the tumors that they did develop were smaller and lighter, with fewer growth factors and less metastasis. Compared with couch-potato mice, their tumor burden was reduced by more than 60%.

The how was even more illuminating. Certain kinds of exercise stimulated a specific immunological response that sent the body’s natural killer immune cells directly into tumors to destroy them—a kind of “immunological spark” that ignites other cells in the immune system to fight cancer, according to the study’s authors.

The key was adrenalin, a “stress” hormone also known as epinephrine. When you exercise vigorously enough to get your heart really pumping, your body sends out more adrenalin—and it’s that adrenalin surge, the researchers report, that stimulates natural killer cells to scour and destroy tumors.

Human studies will be needed to pinpoint exactly how intense exercise needs to be to optimize this immune response. But we already know that exercise that raises your heart rate significantly and makes you break a sweat causes the release of much more adrenalin than milder exercise. You don’t have to be an Olympic athlete to reach those levels. In a recent Health Insider article, we reported that men who exercised three hours a week to the point of sweating—at some point within the exercise session—were much less likely to get aggressive prostate cancer.

Of course, if you’re not fit, you’ll want to start slowly and safely. But becoming fit has its own separate reward—people who exercise regularly and are more fit tend to produce more adrenalin for the same level of exercise intensity compared to less fit people. In short, training boosts the adrenalin response.

If you’re being treated for cancer, it’s understandable if you don’t have much energy for vigorous exercise. Do what you can, and talk with your doctor about ways to get more exercise. Even moderate exercise like walking has wonderful benefits for people undergoing cancer treatment, from reducing nausea to improving muscle tone to enhancing mood. But if you can work out hard, that adrenalin rush may be adding an immunological boost to your cancer fight, too. And once you’ve beaten the cancer, regular heart-pumping exercise may help prevent it from ever coming back.