Research has shown that between 70% and 80% of our immune cells reside in our gut. “In the GI tract, we have millions of different organisms, and a lot of them are there because they need to regulate cellular processes in our body,” explains Dr. Selvi Rajagopal, an assistant professor of medicine at Johns Hopkins School of Medicine. “And we are learning that the more we can support a healthy bacterial environment in our gut, the better chances we have at fending off a lot of inflammatory processes.” 

Food might not be medicine, but optimal nutrition is essential for healthy immune function. The gut microbiome, which refers to the trillions of bacteria that live symbiotically in our GI tracts, depends on a diet rich in vegetables, legumes, nuts, whole grains, and seafood. When the good bacteria in our guts receive a variety of nutrients, immune cells effectively respond to pathogens and wrap up the response as quickly as possible to avoid chronic inflammation. 

“In many ways, the gut is one of our first lines of defense against invaders,” says Dr. Tim Harlan, a professor at George Washington University School of Medicine and director of the GW Culinary Medicine Program.

Give your immune system a boost by reaching for foods rich in these essential nutrients. 

Polyphenols

Red grapes, berries, tree nuts, onions, broccoli, apples, beans, and legumes are an excellent source of polyphenols, which act as anti-inflammatories and help initiate an immune response, explains Clara Di Vincenzo, registered dietician for the Digestive Health Institute at UT Health Austin. 

Prebiotics and probiotics

Prebiotics and probiotics work together to facilitate the growth of healthy gut bacteria, with the former acting as fuel for the latter to do their job. You can get prebiotics by eating garlic, onions, dandelion greens, bananas, flaxseed, cocoa, or asparagus. Probiotics are plentiful in fermented foods such as yogurt, kefir, sauerkraut, miso, and tempe. Prebiotics and probiotics have anti-inflammatory benefits, too. 

Selenium

Brazil nuts, eggs, turkey, brown rice, and fortified foods provide selenium. This mineral stops the immune system from overreacting to pathogens and potentially causing autoimmunity or chronic inflammation. (If eating Brazil nuts, limit yourself to one to three per day.) Zinc, which supports the growth of immune cells, can be obtained by eating poultry, beans, nuts, shellfish, and dairy. In addition, omega-3 fatty acids from fatty fish and chia seeds help your body produce cytokines, which help your immune cells communicate with one another. 

Vitamin A

Green leafy vegetables like collard greens or kale provide vitamin A, which is vital for the immune system even though scientists don’t fully understand why. Vitamin C from citrus fruits, red peppers, kiwis, strawberries, broccoli, and cantaloupe acts as an antioxidant to prevent cells from sustaining damage. Vitamin D regulates the activity of immune cells, stimulates antiviral responses, and reduces inflammation. While it can be obtained from fatty fish and fortified foods, experts suggest speaking with your doctor about supplementation since it’s difficult for many people to get enough from diet alone. (Many of these foods are rich in fiber, too, which helps promote the cellular processes and feed the environment required to support optimal health.) 

Should you choose a supplement?

Supplements can come in handy in certain situations. Animal studies have shown that deficiencies in these key nutrients can negatively alter immune responses. Research has also found that malnourished people are at a higher risk of bacterial and viral infections. For the more than 54 million Americans who live under food apartheid and in food deserts, workarounds like supplements are imperative. 

“It’s not that supplements are not recommended, but we want to consider foods rich in these nutrients before jumping to a magic pill or supplement, knowing that these foods are proven to be more beneficial,” says Di Vincenzo. “And we need that healthy diet to support immune health more than we need just one supplement or a magic pill.”