Cancer cells are different. Instead of feeding on oxygen, as healthy cells do, they thrive on glucose—the sugars in the blood that come from carbohydrates—and this also produces lactate, an acid that allows the cancer to spread.
It’s not news. The process was first observed by German physicist Otto Warburg in 1924 and was then almost completely ignored by the cancer industry, other than by a few maverick outliers who advocated a zero-carb keto diet as part of cancer therapy.
With the discovery of the DNA structure in 1953, cancer theory took a different route and focused on genetic mutations. It was a false trail, and today researchers acknowledge that energy metabolism is the key to understanding cancer’s genesis and spread. It’s estimated that 80 percent of cancers are the result of the “Warburg effect,” as Warburg’s discoveries were labeled.
The one new insight into Warburg’s work is that it is the mitochondria—the powerhouses of cells that convert sugar (carbs), fats and proteins into energy—that are damaged and so become over-reliant on glucose for their rapid growth. Oncologists recognize the phenomenon and routinely use PET (positron emission tomography) scans to seek out areas of the body that are consuming excessive amounts of glucose and therefore to detect cancer.
If the Warburg effect is right, there are other clues in the observation that suggest new ways of treating cancer and, more importantly, preventing it. A team of Israeli researchers has done just that by discovering that aerobic exercise reduces the risk of metastatic cancer—the cancers that spread and are almost always lethal—by 72 percent.1
It’s an enormous effect and one that dwarfs the success rates of the standard treatments of chemotherapy and radiotherapy. As the researchers from Tel Aviv University observed, the process is simple: after bursts of high-impact exercise, our organs and muscles need sugar to replace the stores that were burned up during exercise, and this sudden demand starves cancer cells of their vital supply. Cancers of the lymph nodes, lungs and liver were affected by the competition for glucose and started to shrink.
The researchers noted from a study of around 3,000 people for 20 years that those who did regular aerobic activity at high intensity had 72 percent fewer metastatic cancers than people who didn’t exercise at all. Checking the results with animal tests, they were able to understand the biological mechanism.
After aerobic exercise, our organs develop new glucose receptors, which allows them to swallow up more sugar, and the organs become “energy-consumption machines,” as Carmit Levy, one of the researchers, puts it.
“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,” Levy says. “If cancer develops, the fierce competition over glucose reduces the availability of energy that is critical to metastasis.”
Regular aerobic exercise is the key.
“Exercise changes the whole body so that cancer cannot spread, and the primary tumor also shrinks in size,”
Levy explains.
A high-intensity workout seems to be vital; while moderate, fat-burning exercise is good for our overall health, it does little to block cancer’s spread. If the pulse rate needed to burn fat is up to 70 percent greater than the resting rate, sugar-burning needs to be at a rate that is up to 85 percent higher, if only for brief periods. So, for example, if your resting pulse rate is 70, your sugar-burning rate needs to be around 130.
This rate could be achieved by doing a 1-minute sprint and then walking before running again, says Levy.
Something else could also be happening when we exercise. It produces proteins called myokines, which can suppress tumor growth and even fight cancer cells by stimulating other anti-cancer processes in the body.
Researchers from Edith Cowan University had already discovered that men with advanced prostate cancer could change the chemical environment of their body and stop the cancer progressing just by exercising regularly for six months.
But in an important new study, the same researchers have discovered that myokine levels rise after just a single exercise session. They tested the theory on nine patients with late-stage prostate cancer so advanced that medicine couldn’t help them. The group did 30 minutes of high-intensity exercise on a treadmill, and blood serum taken immediately afterward had higher levels of myokines, which had suppressed cancer cells by 17 percent.2
This dramatic effect lasted for 30 minutes after exercise had finished, after which myokine levels dropped and cancer cells resumed their growth. The researchers aren’t sure of the optimum amount of exercise needed to slow, or stop, cancer’s growth, but they reckon it could be around 20 minutes every day and include resistance training to help muscles grow and “increase the size and capacity of the internal pharmacy,” said Rob Newton, one of the researchers.
The positive effects of exercise on cancer prevention and growth have been seen in several studies in the last decade, although the Israeli researchers are the first to note that the exercise needs to be high-intensity to prevent cancer spreading. In one study, which involved 1.44 million people, the researchers discovered that higher levels of unspecified “leisure-time physical activity” helped protect against 13 cancers.3
Another study, this time involving 755,000 people between the ages of 32 and 91, found that those who exercised for up to 15 hours a week had a reduced risk of developing seven cancers; the biggest impact was on liver cancer, which exercisers showed up to a 27 percent lower risk of ever developing.4
But there’s another player in the Warburg effect that often gets overlooked. Scientists had assumed lactate was an uninteresting waste product from the main process of aerobic glycolysis, in which sugar is burned even when oxygen is present, as Warburg had observed—but researchers are starting to see it playing as central a role as sugar.
While sugar fermentation may kick-start cancer, lactate helps it spread. Lactate—a sign of sepsis and congestive heart failure, but also well known by athletes when they feel their muscles start to stiffen—is a catalyst for cancer, say researchers from the University of Colorado School of Medicine and the University of California, Berkeley. They reckon the molecule has a dual function in cancer: it not only fuels cancer’s spread but serves as its signaling system.
Focus only on sugar in the early stage and the prognosis may not be great, because in the later stages, lactate starts taking on the central role, says Inigo San-Millán, a researcher at the university.5
Just as the Israeli researchers see intense exercise as the response to sugar-burning, so San-Millan prescribes the same to counter lactate. He has devised a series of personalized exercise programs that increase in intensity over a session that can last 30 minutes to an hour on a gym bike or treadmill.
He’s also researching compounds that could block lactate from leaving the cancer cell.
“When lactate is produced, it has to leave the cell through a transporter. We are trying to block the transporter as well as lactate production inside the cancer cell with different compounds. If you block the door, the lactate cannot leave, and the cancer cell will burst,” he says.
As with almost every theory about cancer, exercising it away may not be the definitive answer, even if it does have a dramatic effect on its spread. Top athletes have developed cancer even while doing high-intensity workouts. Perhaps the most famous was cyclist Lance Armstrong, who revealed in 1996 that his testicular cancer had spread to his abdomen, lungs and brain.
But the Israeli researchers say we are just at the dawn of a new era of cancer therapy with high-intensity exercise at its core. Although everyone should include high-intensity exercise in their daily lives, the researchers say the next phase will see more individualized programs being developed to treat specific cancers.
“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,” said Yftach Gepner, another author of the study.
Our regular columnist Dr Leigh Erin Connealy joined us for a discussion about cancer—its origins, the best anti-cancer diet, other ways to prevent it, and strategies to support any treatment you’re having.
Since Erin joined the WDDTY team, we’ve been constantly amazed at her breadth of knowledge about the disease that afflicts so many of us.
Not surprisingly, she is one of the most sought-after cancer specialists in the US, and so we were especially privileged that she is finding time in her busy schedule to talk with us.
