Research has long shown that those who exercise are less likely to get cancer. But a new study is finally helping experts understand why high levels of physical activity inhibit the development and growth of cancer in the body.
The study, published in medical journal Cell Metabolism by a group of Danish researchers, highlighted the effect of exercise on the development of cancer tumors in mice. They did this by implanting cancer cells into all of the mice, but only giving half of the rodents access to a running wheel.
After a month, the mice that had been using the wheel were 60 percent less likely to have developed cancer tumors, and those that had developed the disease typically had less dramatic symptoms than the sedentary group.
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To try to identify the specific effect that exercise may have in preventing cancer in the mice, the researchers did a subsequent experiment where the exercising mice were given a drug that inhibits the development of adrenaline. During this trial, the groups of mice developed cancer at the same rates.
The study thus identifies the result of increased adrenaline as a potentially crucial cancer-fighting mechanism. Or, more specifically, the release of adrenaline led to a chain reaction that led to the activation of "cytotoxic immune cells" that attack cancer cells.
The experts are quick to note that, despite a number of genetic similarities, mice and people are different. So the study does not necessarily provide rock-solid evidence that human exercise unleashes the same reaction that kills off cancer cells. But it might.
Or, as the researchers put it in: "Thus, mobilization of cytotoxic immune cells during exercise might represent an indirect defense mechanism against cancer growth."
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