The same aisle exists in pretty much any drugstore — the one with the powders, pills, chewable tablets, gummies, sprays, and drinks, all claiming to help you stave off or shorten illnesses.
It’s a comforting idea — that a heartier defense system is that close at hand — especially if you’re one of those people who always seems to be coming down with something. But as with almost all quick fixes, this one is mostly too good to be true. There’s no conclusive evidence that “megadosing” on vitamin C will keep you from getting sick. And while there’s some research to suggest that zinc supplements may help shorten the duration of a cold, they won’t prevent you from catching one in the first place.
That’s not to say there’s nothing you can do to build up your immunity over time — it’s just a longer, slower, more involved process. Like a gardener ripping out weeds and planting veggies, the immune system destroys harmful pathogens, promotes helpful bacteria, and maintains an equilibrium in the body. A host of things — certain illnesses, poor diet, aging, a sedentary lifestyle, stress, or a lack of sleep — can weaken your immune system, throwing the delicate balance out of whack. But certain lifestyle changes can strengthen your body’s defense, enabling it to better fight off disease.
Here are a few things you can do to help it along.
Lower your cleanliness standards.
According to Jack Gilbert, PhD, a microbial ecologist, professor, and the author of Dirt is Good: The Advantage of Germs for Your Child’s Developing Immune System, living in a sterile environment free of dirt or antigens can have a detrimental effect on the immune system, especially during childhood. “Your immune system needs to be constantly stimulated in order to be effectively healthy,” Gilbert says. “Bringing up a child in a sterile environment actually makes the immune system more likely to act out and become hyperresponsive.”
A prime example, Gilbert says, is the health disparity between the Amish and Hutterites, two farming communities in the rural United States. In one 2016 study, researchers found that despite genetic and lifestyle similarities between the two communities, the Amish, whose kids spent time on the farm from a younger age, had fewer cases of asthma and allergies than the Hutterites, even though microbial samples from inside the Amish homes yielded more dust and bacteria. The so-called hygiene hypothesis — a theory also cited as a possible explanation for the rise of autoimmune diseases — holds that earlier exposure to a wider variety of microbes acts as constant stimulation of the immune system, Gilbert explains, making it more responsive.
Of course, you were raised how you were raised, and you can’t go back in time to give yourself a childhood with more exposure to dirt. But even as an adult, making a few small tweaks away from constant over-cleanliness could help you become more illness-resistant: Cut down on your use of antibacterial soap, and consider adjusting your shower schedule from daily (which experts generally agree isn’t necessary) to a few times a week. Some doctors have even advocated for more eyebrow-raising behaviors, like eating food that’s fallen on the floor or picking your nose and eating what comes out. We all have our personal thresholds for squeamishness, but the fact is getting more comfortable in a world full of bacteria, rather than trying to scrub away as many as possible, can be helpful in the long run — you need the good ones to help ward off the bad.
Pay more attention to your diet.
One surprisingly critical ingredient for immune health is fiber. The bacteria in your gut, both good and bad, feed on the fiber you get from your meals. But when you don’t get enough fiber, those bacteria start to eat away at the mucus lining the digestive tract, triggering an immune response. (In one study, when mice were fed a high-fat, low-fiber diet and the mucosal lining of their digestive tracts thinned, their intestines became chronically inflamed.) A diet high in fiber — at least 28 grams per day for women and 36 for men, per FDA guidelines — keeps the intestinal lining thick and the microbiome balanced. “Soluble fiber has also been shown to help people recover from bacterial infections faster,” says Dr. Kathleen Dass, an allergist and immunologist based in Oak Park, Michigan. By increasing a protein called interleukin-4, the fiber helps stimulate the body’s production of infection-fighting T cells.
Consuming a wide variety of plants supplies us with an array of crucial nutrients that directly enable the cogs in our immune system to function properly. Vitamin D and vitamin C, for example, have both been shown to stimulate the production of white blood cells. On the other hand, carbohydrates high in simple sugars can decrease white blood cells’ ability to kill bacteria. “You can never go wrong eating a diet full of fruits and vegetables,” says Dass.
Vegetarian diets especially have been shown to decrease chronic inflammation in the body, thanks to the antioxidant properties found in produce. “This effect can actually be shown by measuring an inflammatory marker called C-reactive peptide, or CRP,” Dass says. “Vegetarians tend to have lower levels of CRP than those who do not follow a plant-based diet.”
Go for a walk.
One more way that exercise is beneficial: Research shows that even moderate activity can stimulate the immune system. Although the exact mechanism isn’t yet clear, scientists think exercise stimulates the body to produce cytokines, which regulate local and systemic inflammation as well as other immune responses. Evidence shows that just 20 minutes per day of moderate exercise has immune-strengthening effects.
And if the exercise is outdoors, even better. “Just getting outside for a little bit each day will make sure you’re exposed to a greater diversity of microbes, and that can be beneficial,” Gilbert says. “Obviously, if you live in an industrial wasteland and you’re exposed to toxins or polluted gas, don’t go outside. But if going outside is not going to kill you, then it will actually help your immune system.”