For most of us, our immune system has always been something like the roof over our head: we don’t think much about it unless something goes wrong.
Yet it has always been there, quietly and (mostly) invisibly protecting us against disease, infection, and invaders, from pathogens to parasites — as well as helping us recover from injuries.
But recently the COVID-19 pandemic shook up that thinking, just as it shifted almost everything else in our world. As the toll of the virus mounted, maintaining a healthy immune system moved to the top of everyone’s mind.
All along, to no one’s surprise, the food and supplement industry has responded predictably, rushing to deliver “immune-boosting” supplements and to fortify foods with ingredients touted to “support a healthy immune system.” Indeed, market research suggests that since the pandemic began, some 45% of consumers worldwide are consuming more foods and beverage products aimed at boosting their immune system.
If only it were that easy to tune up our immune system to perfection, just by swallowing the right pills! Truth is, the immune system functions like an exquisitely choreographed dance—many moving parts, all working in synchrony. Add or subtract a single ingredient in the mix and you can upset the balance and defeat the purpose of boosting your immune health. You may even cause harm.
Just look at what happened a few decades ago in the CARET trial, when researchers tested the hypothesis that taking a daily dose of the anti-oxidant nutrients beta-carotene and vitamin A would help prevent lung cancer in people at high risk of the disease (smokers, former smokers and those exposed to asbestos). The premise seemed sound, since studies had shown that people who ate a diet rich in those nutrients were much less likely to develop the diesase. But the trial was halted early when it became clear that not only were the supplements failing to prevent lung cancer, but they were also causing an increased risk of the disease in smokers. (Today the American Cancer Society cautions smokers and former smokers to avoid beta-carotene supplements).
Consider those results another way, though, and they underscore the importance of choosing nourishing foods—not pills—to keep the immune system functioning optimally. Indeed, for many decades now, studies have connected the dots between a well-balanced, nutrient-rich diet and a healthier immune system, as evidenced by lower risk of chronic diseases in people who eat that way.
HERE ARE A FEW BASIC PRINCIPLES TO HELP YOU better understand how the immune system works
Technically your immune system is many systems, encompassing a network of white blood cells, antibodies and other chemicals released by your body’s cells, as well as some of your organs — including a major hub of immune-regulating activity, your gastrointestinal (GI) tract. They all work together to activate, mobilize and attack foreign invaders such as viruses and pathogenic bacteria. Some parts of the immune system “learn” from pathogens you’ve been exposed to, developing antibodies to them so that they can mount a quick defense attack should exposure happen again (this is also how vaccines work).
All these systems are designed to function like a well-oiled machine, but as with any machine, problems can gum up the works. Some are out of our control; for example, the immune system may mistakenly recognize healthy cells as “foreign” and mount an attack against them, manifesting in so-called autoimmune disorders, such
as asthma, allergies, rheumatoid arthritis, celiac disease and more.
As we get older, the immune system tends to become less efficient and less able to ward off infections — one reason we’re more susceptible to illnesses and take longer to recover from them than when we were younger. We may also be exposed to environmental toxins like air and water pollution, which can suppress the activity of immune cells.
But other immune challenges are within our power to change—or at least we have powerful tools to help us manage them. One key factor is stress, which causes the body to release “fight or flight” hormones like cortisol, which can temporarily turn off some of the body’s immune responses to allow it to focus on responding to the stressor. But if the stress is chronic, it can trigger low-grade, systemic inflammation that can damage cells and further challenge the immune system. Negative mental states such as anxiety, depression and loneliness are also associated with a lowered ability to fight off diseases. Likewise, getting the needed psychological and social support can help restore it.
Being overweight or obese can suppress some immune functioning since that too is associated with chronic inflammation. Getting too little sleep can also negatively affect the immune system, since it deprives the body of the restorative processes that help keep immune cells functioning well.
Last, a poor-quality diet can impact the proper functioning of our immune system by suppressing the production and hampering the activity of some immune cells and antibodies. In this case, the prescription is easy, and delicious: a well-rounded diet that’s rich in the immune-supporting nutrients nature provides in abundance in our food supply. Using whole, unprocessed foods rather than sup- plements ensures you’re getting a full package of nutrients, in the balance nature intended.
Here’s a quick roundup of a few key nutrients that science suggests can help the immune system flourish
1. Vitamin C
Vitamin C probably has the longest history of exploration as an immune-boosting nutrient, thanks to work in the 1970s by biochemist Linus Pauling that suggested high doses might shorten the course of the common cold. Even though the megadose theory hasn’t quite stood up to scientific scrutiny, it’s clear that vitamin C, a nutrient our bodies can’t produce and thus must be obtained in food, plays a major role in our immune system. A powerful antioxidant, it helps quench free radicals—highly reactive compounds that can damage cells and lower their defenses against infections. It can also help regenerate other antioxidant nutrients, further helping quell inflammatory pro- cesses. Foods rich in vitamin C include citrus fruits, peppers, kiwi fruit and cruciferous vegetables like broccoli and cabbage.
2. Vitamin D
Vitamin D also promotes anti-inflammatory activity, and it’s involved in the production of antibodies. Preliminary studies suggest vitamin D might also help protect against some autoimmune diseases, since low levels are associated with a higher risk of multiple sclerosis, diabetes and other auto- immune-related disorders. Our bodies produce vitamin D when we expose our skin to sunlight, but it’s tough to get enough that way if you use sunscreen (as many of us do) or live in a northern climate, especially in the winter. It’s also challenging to get enough of the vitamin from foods alone, so in this rare case, you’ll likely need supplements. You’ll find some D in fatty fish, liver and egg yolks and in fortified foods, including dairy products and plant-based dairy foods, cereals and juices.
3. Vitamin A
Vitamin A (retinol) and plant-based provitamin A compounds called carotenoids have a strong anti-oxidant activity that keeps the immune system functioning smoothly (see vitamin C, above); both help support the growth and activity of immune cells. Adequate vitamin A also helps maintain a healthy skin barrier—a key part of your immune defenses. While animal products like liver, fish oils and egg yolks are good sources of vitamin A, it’s a good idea to focus more on carotenoid-rich fruits and vegetables, which your body can convert as needed to vitamin A with no risk of getting too much. Good sources are leafy green vegetables and orange and red fruits and vegetables, such as peppers, tomatoes and cantaloupe.
4. Probiotic and Prebiotic
Probiotic and prebiotic foods also have anti-inflammatory actions, and they fortify the immune defenses of the microbiome—the complex system of microorganisms that populate our GI tract. Probiotic foods contain beneficial bacteria that help strengthen the lining of the GI tract while producing compounds that protect it from pathogenic organisms. Also important are prebiotic foods, rich in the stuff those beneficial organisms feed on: fiber and compounds called oligosaccharides. The probiotic bacteria in the GI tract break down those prebiotic products, turning them into fatty acids that help boost the activity of some immune cells. Probiotic bacteria are found in fermented foods, such as yogurt, kefir, kombucha, kimchi, miso and sauerkraut; prebiotic-rich foods include fiber-rich fruits, vegetables and beans—particularly onions, leeks, asparagus and bananas.
To state the (by now) obvious, it’s clear that a well-nourished body is a strong defense against disease. It’s also true that the factors that keep us happier, healthier and more energetic, such as being active regularly, maintaining a healthy weight, getting enough sleep, managing stress and staying socially engaged, can also help foster good immune health.
In fact, “immune support” has always been largely within our reach—and much depends on what we choose to put on our plates. Read on to discover how satisfying those choices can be.