Probably the scariest thing about cancer is the possibility that it will spread (metastasize) beyond the original tumor site.
A new study led by researchers from Tel Aviv University’s medical school offers a remarkably effective and drug-free way to prevent metastasis: aerobic exercise.
Intense aerobic exercise can reduce the risk of metastatic cancer by 72 percent, according to study leaders Prof. Carmit Levy (TAU department of human genetics and biochemistry) and Yftach Gepner (TAU School of Public Health and Sylvan Adams Sports Institute).
While previous studies have demonstrated that physical exercise reduces the risk of cancer incidence and recurrence for some types of cancer by up to 35%, the Israeli researchers wanted to find out why.
They discovered it’s because an intense aerobic workout increases the glucose (sugar) consumption of internal organs, thereby starving the tumor of energy to spread.
“If so far the general message to the public has been ‘be active, be healthy,’ now we can explain how aerobic activity can maximize the prevention of the most aggressive and metastatic types of cancer,” Levy and Gepner said in a statement.
“It must be emphasized that physical exercise exhibits a higher level of cancer prevention than any medication or medical intervention to date.”
They also discovered that high-intensity aerobic exercise is especially effective at starving the tumor of glucose, doubling the preventative effect.
The study’s significance is underlined by the fact that it was chosen as the cover story of the November 2022 issue of the journal Cancer Research.
The study combined an animal model in which mice were trained under a strict exercise regimen, with data from healthy human volunteers examined before and after running.
Of mice and men
The human data, obtained from an epidemiological study that monitored 3,000 individuals for about 20 years, indicated 72% less metastatic cancer in participants who reported regular aerobic activity at high intensity, compared to those who did not engage in physical exercise.
The animal model exhibited a similar outcome, also enabling the researchers to identify its underlying mechanism.
Sampling the internal organs of the physically fit animals, before and after physical exercise, and following the injection of cancer, they found that aerobic activity significantly reduced the development of metastatic tumors in the lymph nodes, lungs and liver.
The researchers hypothesized that in both humans and model animals, this favorable outcome is related to the enhanced rate of glucose consumption induced by exercise.
“Our study is the first to investigate the impact of exercise on the internal organs in which metastases usually develop, like the lungs, liver, and lymph nodes,” said Levy.
“Examining the cells of these organs, we found a rise in the number of glucose receptors during high-intensity aerobic activity — increasing glucose intake and turning the organs into effective energy-consumption machines, very much like the muscles,” she continued.
“We assume that this happens because the organs must compete for sugar resources with the muscles, known to burn large quantities of glucose during physical exercise. Consequently, if cancer develops, the fierce competition over glucose reduces the availability of energy that is critical to metastasis.”
Even better: When a person exercises regularly, the tissues of internal organs change permanently and become similar to muscle tissue.
“We all know that sports and physical exercise are good for our health. Our study, examining the internal organs, discovered that exercise changes the whole body, so that the cancer cannot spread, and the primary tumor also shrinks in size,” Levy said.
It must be intense
Gepner emphasized that only high-intensity aerobics, not moderate fat-burning exercise, helps prevent cancer metastasis.
“If the optimal intensity range for burning fat is 65-70% of the maximum pulse rate, sugar burning requires 80-85%, even if only for brief intervals,” he said.
This could be accomplished, for example, by a one-minute sprint followed by walking and then another sprint.
“In the past, such intervals were mostly typical of athletes’ training regimens, but today we also see them in other exercise routines, such as heart and lung rehabilitation,” said Gepner.
Based on the study’s findings, he encourages healthy individuals to include high-intensity components in their fitness programs.
“We believe that future studies will enable personalized medicine for preventing specific cancers, with physicians reviewing family histories to recommend the right kind of physical activity,” Gepner said.
“It must be emphasized that physical exercise, with its unique metabolic and physiological effects, exhibits a higher level of cancer prevention than any medication or medical intervention to date.”
The study’s 40 authors include experts from Hebrew University of Jerusalem, Technion-Israel Institute of Technology, Tel Aviv Sourasky Medical Center, Sheba Medical Center, Wolfson Medical Center, the Israeli Ministry of Health and the Israel Center for Disease Control.