If there has ever been a time to focus on keeping your immune system healthy, this long winter of the pandemic is it. As the ongoing coronavirus crisis hits it darkest hour yet, we have the cold and flu season to contend with, too. Amid these ongoing threats, the notion that we might somehow “boost” our immune system with one weird trick — an herb, a supplement, a particular food — holds obvious appeal.

If only it were that simple.

When it comes to bolstering the immune system, “a lot of people just want a quick fix or magic pill,” says Cristina Porch-Curren, an allergist and immunologist in private practice in Ventura County, Calif. Unfortunately, there’s no such thing, she says. If that’s disappointing, there’s still some good news: the most scientifically sound approaches to keeping your immune system healthy are healthy habits that don’t require you to buy pills or eat strange foods.

From practicing mindfulness to spending time outdoors, here are some tips for overcoming what some are calling “pandemic fatigue” and avoiding burnout. (Drea Cornejo/The Washington Post)

One of the most effective ways to improve your immune system's health is by reducing stress. Researchers have known for a long time that stress can hamper the immune system, Porch-Curren says.

For instance, a study published in the New England Journal of Medicine back in 1991 found that when researchers gave volunteers nasal drops containing common respiratory viruses, participants who reported higher levels of psychological stress were more likely to become infected and develop symptoms of the common cold compared with people who had lower stress levels. The more stressed the volunteers were, the greater their chances of becoming sick.

More recently, a 2004 review summarizing 30 years of research and more than 300 studies on stress and immunity concluded that chronic stress can cause measurable suppression of the immune system. It said that even short-term stressors, such as academic exams, can impair the body’s immune response.

You probably cannot eliminate stress from your life in this time of uncertainty, but anything you can do to manage or reduce it will be helpful, Porch-Curren says.

The federal Substance Abuse and Mental Health Services Administration offers tips for managing distress during a pandemic that includes building social connections, managing negative thoughts, maintaining a sense of humor, getting outside, and finding ways to relax, such as listening to music or meditation.

Meditation is a well-known approach to managing stress, and it comes with another benefit — it may also help you sleep better. A randomized, controlled trial published in JAMA Internal Medicine in 2015 found that meditation could produce “robust improvements in sleep among older adults,” says the study’s senior author, Michael Irwin, a psychiatrist at the UCLA Geffen School of Medicine where he directs the Mindful Awareness Research Center.

Sleep is crucial to maintaining a robust immune system.

“We know that sleep problems, especially difficulties maintaining sleep, make you more susceptible to viral infections,” Irwin says. His research has shown that even modest amounts of sleep loss can increase the production of signaling molecules that promote inflammation and make someone more prone to illness. “Even one night of disturbed sleep can have an impact,” he says.

One phenomenon Irwin has been tracking is how health-care workers often experience particularly serious outcomes from covid-19, the disease caused by the coronavirus. (A report published by the National Nurses United in September estimated that more than 1,700 health-care workers in the United States have died of covid-19.) Although some of this is probably a result of them being exposed to high doses of covid-19 in their work, Irwin also suspects that lack of sleep may play a role.

“We know that many of them are experiencing huge sleep debts because of scheduling and the long hours and night shifts they’re working,” he says.

To keep your immune system healthy, it’s important to maintain a regular sleep schedule, Irwin says. “That means going to bed at the same time and waking up at the same time every day.” Go easy on the alcohol, which can interfere with sleep, especially the deep sleep that Irwin calls especially critical for your body’s antiviral immune response.

Exercise can also improve your sleep — according to the American Academy of Sleep Medicine, even small amounts of physical activity can help you sleep better. But it comes with a huge added bonus: It helps your immune system become better prepared to fight off viral attacks, too, researchers have found.

Regular physical activity at moderate intensity — enough so that you’re breathing a little harder and your heart is pumping a little faster — improves the immune system’s surveillance against pathogens and reduces the chances of getting sick or dying from viral infection and respiratory illnesses, including the common cold, pneumonia and influenza, says David Nieman, an exercise physiologist at Appalachian State University. Thus, it may reduce your chances of getting sick at all. Nieman has conducted numerous studies on exercise and the immune system. Last year, he published a review of research over the past century regarding the relationship between exercise and the body’s immune defense system, which concluded that there’s “a clear inverse relationship between moderate exercise training and illness risk” and “habitual exercise improves immune regulation.”

Experiments have shown that exercise stimulates the recruitment of the immune system’s best fighter cells, Nieman says. “What exercise does is it signals the best fighters to come out and patrol the body at a higher rate than normal.”

It doesn’t take much to get these effects. Something as simple as a 30 to 45 minute brisk walk is enough to activate this immune response, which studies show begins during exercise and lasts several hours afterward, Nieman says. If you exercise day after day, “It’s like the military patrolling the countryside. You’re going to keep the enemy controlled a lot better as time goes on than if you haven’t done this patrolling.”

Nieman’s review concluded that exercise is associated with a 40 to 45 percent reduction in the number of sick days people experience from acute respiratory infections. The research done so far has found this effect for the common cold, influenza and pneumonia, but Nieman thinks that “it’s only a matter of time before we find that the coronavirus also responds in a similar fashion.”

If you’ve noticed that the list so far of scientifically confirmed approaches to maintaining immune system function essentially amounts to a set of common tips for improving one’s overall health, you can probably guess the final component that experts point to: nutrition. The Internet is littered with lists of “superfoods” that supposedly bolster the immune system, but Rene Leon, a clinical immunologist at Texas Regional Allergy and Asthma Center, says he doesn’t advise his patients to eat superfoods for their immune systems — in fact, “absolutely not.” If there was a food or subset of foods that would help patients improve their immune response, immunologists would be the first to say so, he says. “But we don’t, because I don’t think there’s any hard science to prove that.”

Nutrition is definitely important to staying healthy, but “you can’t just say, ‘I’m going to eat blueberries,’ because they’re full of antioxidants,” Porch-Curren says. Single foods aren’t the key to bolster immunity. Instead, it’s the totality of your diet that matters. If you’re trying to maintain a healthy immune system, the best approach is to eat a well-balanced diet with an emphasis on whole foods rather than processed ones, she says.

Despite the heavy marketing, there’s no vitamin or nutritional supplement that can magically bolster your immune system, experts say. Leon regularly works with patients who have suppressed immune systems because of diseases and genetic conditions. He says that if an easy immune booster really existed, he would jump at the chance to point his patients to it.

“There are a lot of bogus claims out there,” Leon says. Pay attention to the fine print, he says. “If there’s a disclaimer on there that says that [the product] doesn’t treat or cure any disease, then the proof is in the pudding.”

“I have patients who come in with a box of supplements and so many different bottles,” Porch-Curren says, but “none of them” have cured their immune deficiencies with any of these products.

When these things seem to work, it’s usually because of a placebo effect, and that might make it seem like there’s no harm in trying them. But diet, weight loss and sex supplements are tainted with unapproved drugs. In a single month of 2015 alone, for instance, the Food and Drug Administration issued warning letters to 14 companies selling supplements tainted with an illegal drug. And even seemingly harmless ingredients can cause health issues — such as liver toxicity reported by one doctor writing in The Washington Post.

It’s human nature to look for a quick fix, but there’s no single thing you can do to fortify your immune system, Porch-Curren says. The best way to bolster your immune system against covid-19 is with one of the vaccines now being rolled out across the United States.

Beyond that, the best approach to fortifying your immune system is to aim for an overall healthy lifestyle, Porch-Curren says.

“If you exercise more, you’ll sleep better. If you sleep better, your immune system is more functional,” she says. Add on to that a diet that’s rich in vitamins and whole foods, and you will be on your way to a more resilient immune system.