That amount of exercise made the immune system more able to stamp out cancer cells, researchers at the found. The intervention was specific by design, said Eduardo Vilar-Sanchez, MD, PhD, a professor of clinical cancer prevention at the University of Texas MD Anderson Cancer Center, Houston, and the study’s lead author.
“We wanted to be very concrete on the recommendation,” he said. “People don’t adhere to vague lifestyle advice like ‘just exercise.’ We wanted to link a specific biologic effect to a very concrete intervention.”
The study was small (just 21 people), but it builds on a vast body of evidence linking regular exercise to a decreased risk of cancer, particularly colorectal cancer. But the researchers went a step further, investigating how exercise might lower cancer risk.
Exercise and the immune system
All 21 people in the study had Lynch syndrome, and they were divided into two groups. One was given a 12-month exercise program; the other was not. The scientists checked their cardio and respiratory fitness and tracked immune cells – natural killer cells and CD8+ T cells – in the blood and colon tissues.
“These are the immune cells that are in charge of attacking foreign entities like cancer cells,” Dr. Vilar-Sanchez said, “and they were more active with the participants who exercised.”
People in the exercise group also saw a drop in levels of the inflammatory marker prostaglandin E2 (PGE2). The drop was closely linked to the increase in immune cells. Both changes suggest a stronger immune response.
The researchers believe the changes relate to a boost in the body’s “immune surveillance” system for hunting down and clearing out cells that would otherwise become cancerous.
Building on prior research
Science already offers a lot of support that regular exercise can help prevent cancer. A massive 2019 systematic review of more than 45 studies and several million people found strong evidence that exercise can reduce the risk of several cancers – including bladder, breast, colorectal, and gastric cancers – by up to 20%.
But the MD Anderson study is the first to show a link between exercise and changes in immune biomarkers, the researchers said.
“One thing is having the epidemiological correlation, but it’s another thing to know the biological basis,” added Xavier Llor, MD, PhD, a professor of medicine at Yale University, New Haven, Conn, who was not involved in the study.
Two previous studies looked at exercise and inflammation markers in healthy people and in those with a history of colon polyps, but neither study produced meaningful results. This new study’s success could be caused by the higher-intensity exercise or extra colon tissue samples. But also, advances in technology now allow for more sensitive measurements, the researchers said.
Wider implications?
Dr. Vilar-Sanchez hesitated to extend the study findings beyond people with Lynch syndrome, but he’s optimistic that they may apply to the general population as well.
Dr. Llor agreed: “Exercise could be protective against other types of cancer through some of these mechanisms.”
According to the American Cancer Society, more than 15% of all cancer deaths (aside from tobacco-related cancers) in the United States are related to lifestyle factors, including physical inactivity, excess body weight, alcohol use, and poor nutrition. It recommends 150-300 minutes of moderate-intensity exercise a week to reduce cancer risk. People in the study saw a significant immune response with 135 minutes of high-intensity exercise a week.
“The public should know that engaging in any form of exercise will somehow lead to effects in cancer prevention,” Dr. Vilar-Sanchez said.
A version of this article appeared on WebMD.com.