There is no doubt that regular exercise provides a wide array of health benefits. Just 30 minutes of activity a day can help increase energy, improve quality of sleep, and maintain a healthy weight. Yet another impressive advantage of maintaining an active lifestyle is better management of medical conditions. Studies have shown that participating in frequent workouts promotes good cholesterol and ensures that blood flows easily throughout the body. As such, general practitioners extol exercise as an excellent means of controlling such health conditions as arthritis, type 2 diabetes, and stroke.
In the last several years, researchers have discovered an even more significant benefit of exercising on a regular basis. Protection against the spread of cancer seems an unlikely byproduct of hitting the gym, but there is substantial scientific evidence that supports this claim. Though there have been numerous research studies that analyze the effects of aerobics on tumor growth, a team from Denmark’s Center for Physical Activity (CPA) at Copenhagen University Hospital have unlocked several long-standing mysteries about the more specific process of exercise’s effect on the spread of cancer.
A Developing Problem
According to the World Health Organization (WHO), a number of common cancers remain the most prominent causes of mortality across the globe. Over the next 20 years, the number of new cancer diagnoses are reportedly expected to increase by 70 percent to a staggering 22 million cases per year. These statistics have created an unprecedented need to develop a deeper understanding of the underlying conditions surrounding the prevention of cancer.
This is where the recent work of the CPA comes in. For years, cancer researchers have recognized that exercise triggers a unique response of the body’s natural killer (NK) cells, which are a prominent element of the body’s immune system. A variation of the lymphocyte, these cells are major players in the fight against the spread of infected cells and the growth of cancerous tumors. While it is well known that an active lifestyle causes an increase in the activity of NK cells, experts do not yet know how these two elements come together to fight against cancer.
The Introduction of Voluntary Exercise
In an article published in the March 2016 edition of Cell Metabolism, the Danish team at Copenhagen University Hospital presented their findings after analyzing the growth of cancerous tumors in lab mice. Under the guidance of researcher Dr. Pernille Hojman, the team conducted a series of trials on the mice, some of which received access to running wheels and some whose daily activity was limited to their general movement around their cages. With these set parameters, the researchers then injected the mice with an inducing agent that heightened their risk for developing cancer. One group of mice received tail injections of melanoma cells, a procedure that is known for causing rodents to develop melanoma growths in their lungs. At the same time, the researchers gave another group shots of diethylnitrosamine, which is known to cause liver cancer.
Over the course of six weeks, Dr. Hojman and her team monitored the activity of the mice and found that those who had access to wheels ran between four and seven kilometers every day. At the end of this initial trial, they found a number of surprising results. In fact, more than 60 percent of active mice displayed minimized melanoma-related tumors, with a comparable amount experiencing a reduction in lung masses. In addition, the mice who displayed the condition had either fewer cancerous lesions or ones that were smaller than those on their more sedentary counterparts. In the mice who had received diethylnitrosamine, 75 percent of non-active subjects developed tumors during the study, while only about 30 percent of those with access to wheels had any cancerous masses.
Understanding the Results
Recognizing exercise’s efficacy at preventing the formation of melanoma, lung, and liver malignancies, the team at CPA took additional steps to discover the reasons as to why exercise elicits these results. Upon taking blood samples from both groups of mice, they found a number of differences between them. The mice who had spent weeks with access to running wheels had higher levels of adrenaline than the other subjects. The researchers also found that more activity caused a greater release of interleukin-6 (I-6), a protein that better enables the body’s immune system to fight tumors. With more of these proteins, the active mice possessed a drastically higher amount of immune cells such as T-cells and NK cells.
The NK cells were the key to the reduced size of tumors. In a subsequent experiment, Dr. Hojman removed these immune cells from the active mice. Without the NK cells infiltrating the malignancies and preventing them from increasing in size, they were able to grow just as they did in the sedentary mice.
These findings helped unlock the mystery surrounding the relationship between exercise and tumor prevention. Dr. Hojman and her team were able to conclude that exercise was the direct cause of the reduced size and amount of malignancies in the mice. More specifically, the studied mice achieved these effects through intensive training in particular.
Further Scientific Steps
The results of these experiments have encouraged Dr. Hojman to pursue studies on humans who have been diagnosed with cancer. Generally, she hopes to analyze the relationship between exercise and standard immunotherapy and chemotherapy treatments. Dr. Hojman particularly hopes to look at patients receiving checkpoint blockade therapy, which helps prevent cancerous growths from sending signals that cause the immune system to view them as benign. With exercise facilitating the enhanced release of immune cells, this could help make checkpoint blockade therapy more effective. If this proves to be a success, it could very well make exercise an effective supplement to standard cancer treatments.
Such a level of exercise may not be achievable for many, particular in those who are elderly or infirm. However, Dr. Hojman believes epinephrine is a possible solution. When injected into the less active mice, this hormone helped minimize tumor growth by an excess of 60 percent. The CPA team was thus able to conclude that epinephrine, when paired with I-6 proteins, could one day serve as an effective means of preventing the growth of tumors in humans.