You’ve probably heard the advice: One of the best things you can do to stay healthy — especially as cold and flu season creeps in — is to stay physically active.
This folk wisdom has been around for a long time, but until recently, researchers didn’t have much data to support the idea. Now, scientists studying risk factors for Covid-19 have found some preliminary evidence about the relationship between regular exercise and improving immune defenses against the disease.
When researchers reviewed 16 studies of people who had remained physically active during the pandemic, they found that exercise was associated with a lower risk of infection as well as a lower risk of severe Covid-19. analysis, Published in the British Journal of Sports MedicineIt has generated a lot of enthusiasm among exercise scientists, who say the findings could lead to updated guidelines for physical activity and health care policy revolving around exercise as medicine.
Experts who study immunology and infectious diseases are more cautious in their interpretation of the results. But they agree that exercise can help protect health through several different mechanisms.
Exercise can boost immunity
For decades, scientists have observed that people who are fit and physically active appear to have lower rates of many respiratory infections. When people who exercise get sick, they tend to have less severe disease, said David Neiman, a professor of health and exercise sciences at Appalachian State University, who was not involved in the recent Covid review. “The risks of severe outcomes and deaths from colds, flu and pneumonia – all have been eliminated to some extent,” said Professor Nieman. “I call it the vaccine-like effect.”
The new meta-analysis, which looked at studies between November 2019 and March 2022, found that this effect extends to Covid. People around the world who exercised regularly had a 36 percent lower risk of hospitalization and a 43 percent lower risk of dying from Covid than those who were not active. They also have a lower chance of contracting Covid at all.
People who follow the guidelines that recommend at least 150 minutes of moderate activity or 75 minutes of vigorous activity per week seem to get the most benefit. But even those who exercised less were more protected from disease than those who did not exercise at all.
Researchers hypothesize that exercise may help fight infectious bacteria and viruses by increasing the turnover of immune cells in the blood, for example. In some small studies, researchers also found that muscle contraction and movement release signaling proteins known as cytokines, which help immune cells direct them to find and fight infections.
Professor Niemann said that even if your levels of cytokines and immune cells drop two or three hours after you stop exercising, your immune system becomes more responsive and able to pick up pathogens faster over time if you exercise every day. “Your immune system is primed, and it’s in a better fighting position to handle the viral load at any given time,” he said.
In healthy humans, physical activity has also been linked to a decrease in chronic inflammation. Diffuse inflammation can be so harmful that it even turns your own immune cells against your own body. Professor Niemann said it is a known risk factor for Covid. So, it makes sense that reducing inflammation could improve your chances of fighting infection, he said.
Research also shows that exercise may amplify the benefits of some vaccines. For example, people who worked immediately after getting the Covid-19 vaccine seemed to produce more antibodies. And in studies of older adults who were vaccinated early during the flu season, those who exercised had antibodies that persisted throughout the winter.
Exercise offers a slew of broader health benefits that may help reduce the incidence and severity of disease, said Dr. Stuart Ray, an infectious disease specialist at Johns Hopkins University School of Medicine. Building a walk, jog, gym trip, or favorite sport into your routine is known to help reduce obesity, diabetes and heart disease, for example, all of which are risk factors for severe flu and Covid. Exercise can help you get more restful sleep, boost your mood, improve insulin metabolism and cardiovascular health, and improve your chances of fighting the flu and COVID-19. Dr. Ray said it’s hard to tell if the benefits come from direct changes in the immune system or just better health in general.
Research can only tell us so much
Dr. Peter Chen Hong, an infectious disease specialist at the University of California, San Francisco, agreed that more research is needed before scientists can identify a specific mechanism or causal relationship. In the meantime, he said, it’s important not to over believe in him. “Right now, you can’t say, ‘I’m going to the gym so I can prevent Covid-19,’” Dr. Chen Hong said. “The problem with studying the exact effect of physical activity on immunity is that exercise is not something that scientists can measure,” said Dr. Chen Hong. easily on a linear scale.“People exercise in many different ways.”
Study participants typically self-report the amount and intensity of their exercise, which can often be inaccurate. And only expecting exercise to be beneficial can provide a strong placebo effect. As a result, it can be difficult for researchers to determine the ideal amount or type of exercise for immune function. It’s also very likely that people who exercise regularly may share other traits that help them fight infection, Dr. Ray said, such as eating a varied diet or improving access to medical care.
Furthermore, “there is a huge debate about whether excessive exercise makes you more susceptible to infection and disease,” said Richard Simpson, who studies physiology and immunology at the University of Arizona.
Marathon runners often get sick after races, Simpson said, and some researchers believe that intense exercise may inadvertently overstimulate cytokines and inflammation in the body. Uninterrupted exercise also depletes the body’s glycogen stores, which for some people can lead to poor immune function for a few hours or a few days, depending on their underlying health, he said. Exercising in groups or attending intense sports training camps can expose athletes to more pathogens. Other experts suggest that physically active people may monitor their health closely.
However, for the average trainee, early evidence suggests that there may be a protective effect against developing severe disease. Dr. Ray said those who find it difficult to get enough exercise or cannot exercise at all for some reason should not give up. “What helps one person stay healthy compared to another is a complex mix of factors,” he said. – This article originally appeared in The New York Times