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8 Best Immune-Boosting Supplements That Work, Say Doctors

Vitamin deficiencies can sap your body's ability to fend off viruses. Make sure you're getting enough of these nutrients from food and supplements.

While riding the crest of the COVID-19 pandemic in the middle of cold and flu season, you may be wondering which vitamin supplements to take to bolster your immune system and provide extra protection against whatever sneaks through your mask.

Before we suggest which pills to consider popping, remember what doctors say: the best immune-boosting supplement is not something that you buy over the counter and swallow with a glass of water. It's more important to follow a healthy diet rich in foods that contain immune-supporting nutrients. It's also important to get good sleep. Clinical studies have proven that extra sleep is your most powerful supplemental insurance to avoid getting sick. Research strongly suggests that sleep strengthens your immune system's ability to remember invading pathogens like viruses and mount the proper defenses against them.

Inadequate sleep is not the only arrow that can pierce holes in your body's immune defense. Stress, being out of shape, being overweight or obese, undernourishment, and nutritional deficiencies all can impair immune system responses. "Sometimes the 'healthiest' of eaters aren't eating the right foods for a proper balance and absorption of nutrients, so that's why supplements are often needed," says Nicole Avena, PhD, a research neuroscientist at Mount Sinai Medical School in New York and author of What to Eat When You're Pregnant. "You can work on filling nutritional gaps in your diet that could lead to nutrient deficiencies."

No one food or supplement can prevent illness, but good nutritional variety, including vitamins A, B6, B12, C, E, probiotics, protein, and zinc on a regular basis, may offer protection from seasonal illnesses, according to The Academy of Nutrition and Dietetics, and doctors, and nutritionists we consulted. Read on to find out which nutrients you should stock up on to bolster your immune system, and for more on healthy eating, don't miss 7 Healthiest Foods to Eat Right Now.

Learn Your A,B,Cs

man taking supplement

"The best way to get your vitamins is through your food sources," says Arielle Levitan, MD, an internal medicine physician, co-founder of Vous Vitamin and co-author with Rony Block, MD, of The Vitamin Solution: Two Doctors Clear the Confusion About Vitamins and Your Health. But your food may not be enough. "Even people who concentrate on eating enough fruits and vegetables can have trouble, because a lot of the food consumed comes from nutrient-depleted soil or have nutrient deterioration at the time of consumption," Dr. Levitan says. "Many people need to supplement their diet with vitamins. And while there is no vitamin regimen to prevent illness, including COVID-19, taking the right vitamins can definitely help boost your immune system."

All the experts contacted for this article stressed the importance of taking a personalized approach to selecting vitamins and minerals based on your needs and specific health issues and being aware of potential interactions with medications and other supplements. Consult your primary care physician to determine which supplements are safest for you.

"Remember, the FDA does not test for purity of supplements, so companies can market and label supplements as they wish," says clinician-scientist Florence Comite, MD, founder of the Center for Precision Medicine & Health in New York City, and author of Keep It Up.

While shopping for the vitamins listed below, look for products that are tested by third-party labs. "Even if testing is available, companies sometimes test these products but do not necessarily stay vigilant," says Dr. Comite. "Ideally, look for institutions that have a methodology for validity and keep on top of that methodology."

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Probiotic pill supplement

Swallowing even the best supplements won't do much good if your body doesn't absorb those beneficial nutrients. "We need to address gut inflammation first because an unhealthy gut does not allow for the proper absorption of nutrients," says Alexander Lightstone Borsand, MD, a board-certified lifestyle medicine physician in Scottsdale, Arizona. "This starts with probiotics and an anti-inflammatory diet. We need to first decrease sugars and red meat, which can cause inflammation, swelling, and 'leaky gut:' the inability to absorb the nutrients needed to enhance our immune system."

A diet that combats inflammation includes vegetables, fruits, whole grains, fatty fish, plant-based proteins, and fresh herbs. Only after healing an inflamed gut can you effectively begin to grow the healthy gut flora that studies suggest may bolster immunity, says Dr. Borsand.

"The gut is said to house the immune system, and the delicate balance of the microbiome is important to keep the immune system strong and operating efficiently," says nutritionist Lisa Richards, author of The Candida Diet. "Probiotic supplements can be an effective means of giving your immune system the extra boost it needs to get through a time of significant illness."

For example, one clinical trial recruited people age 45 and under who reported getting the common cold or flu at least four times during the previous year. The double-blind, placebo-controlled trial tested people given a probiotic yogurt drink daily containing Lactobacillus and Bifidobacterium against subjects given a placebo drink containing no probiotics. After 12 weeks, the participants who drank the probiotic yogurt experienced less than half of the upper respiratory infections that the placebo group did. In addition, the probiotics group showed significantly higher levels of immunoregulatory substances.

Vitamin C


Ascorbic acid, better known as the water-soluble vitamin C, is what's called an "essential vitamin" because our body doesn't make it. You have to get this nutrient from your food or from supplements. Vitamin C has been long touted for its immune-boosting benefits of stimulating the formation of antibodies.

"Vitamin C is the queen of all-natural immune boosters," says Carrie Lam, MD, co-founder of the Lam Clinic of Integrative Medicine in Tustin, CA. "It's a powerful antioxidant that's crucial for the health of capillaries, skin, teeth and bones and one of the most commonly recommended adrenal fatigue supplements."

Vitamin C plays an important role in the creation of white blood cells that help fight infection and disease. It has been shown to accelerate wound healing and reduce the risk of heart disease. While getting vitamin C in your diet is critical for preventing immune system deficiencies, there's not much clinical evidence that this immune booster nutrient can prevent colds or flu. Instead, studies of the effects of regular vitamin C supplementation have shown a modest 8% reduction in the duration of the illness in adults and a 14% reduction in children. Vitamin C also appeared to reduce the severity of symptoms.

"Vitamin C is generally safe to take as a supplement long-term even at relatively high doses so it's a great addition to most supplement regimens as a means to defend against illnesses that could exacerbate symptoms," says Trista Best, RD, a nutritionist and environmental health specialist at Balance One Supplements in Delaware.

Vitamin D

Pill bottle

Vitamin D is often called "the sunshine vitamin" because our bodies naturally produce it when we expose our skin to the sun. Is it any wonder then that an uptick in seasonal colds and flu coincides with wintertime when there's little opportunity to bask in natural sunlight and many people have very low levels of vitamin D in their bodies? A 2017 meta-analysis published in the British Medical Journal showed that taking vitamin D supplements daily could help prevent colds and flu, especially in those people who were deficient in vitamin D. A separate more recent study found that vitamin D supplementation can decrease viral respiratory infection by 70% in people who are vitamin D deficient.
"Vitamin D is important to the function of the immune system and vitamin D supplements have previously been shown to lower the risk of viral respiratory tract infections," said David Meltzer, MD, chief of hospital medicine at the University of Chicago Medicine and lead author of a recent study on vitamin D published in JAMA Network Open. "Our statistical analysis suggests this may be true for the COVID-19 infection."

Before you rush to stock up on vitamin D, however, a precaution: "Vitamin D has lately surged in popularity and there is some evidence that people are over-consuming it," warns Dr. Jessica Nouhavandi, PharmD, and co-founder of Honeybee Health, an online pharmacy in Los Angeles, in a blog post. "For most people, the recommended dose of vitamin D daily is 600 to 800 international units (IU)." A recent national survey pointed to an 18% increase in the number of people taking 1,000 IU or more daily.

Related: 5 Signs of Vitamin D Deficiency You Should Never Ignore

Vitamins B12 and B9


Studies suggest that getting adequate amounts of vitamins B12 (cobalamin) and B9 (folic acid) based on individual needs is critical for immune system strength. "If there's one place in the body that is the control center of immune response, it would be the pituitary gland, and this gland has the highest concentration of B12 in the body," says nutritional psychiatrist Sheldon Zablow, MD, author of Your Vitamins are Obsolete. "So, a deficiency of B12 will adversely affect the body's ability to heal and grow with a balanced immune response." Dr. Zablow points out that B vitamin deficiencies, including inadequate folate, can trigger the immune system to overreact, causing chronic inflammation, "the source of nine out of the 10 leading causes of illness and death," he says. Zablow recommends high-quality B12 and folate supplements because "current multivitamins contain B vitamins that are poorly made, poorly absorbed, and poorly metabolized," he says. We're fans of wellmade by Thrive Market's Methyl B-12: these vegan supplements are made with high-quality, ethically sourced ingredients, and are produced by following strict, FDA-regulated standards for quality and safety. Thrive Market also always thoroughly tests their supplements for potency and purity.

Elderberry Extract and Zinc


Elderberry extract, honey, ginger, garlic, echinacea, and about a dozen other plants and herbs have been used as folk remedies for colds and flu for centuries. While they may not turbocharge your immune system, some studies show they offer relief and even speed recovery from these seasonal maladies. Zinc lozenges (but not zinc supplements in pill form) may help reduces symptoms of the common cold if taken with 23 hours of the start of symptoms, according to the National Institutes of Health. But more study is needed to determine the most effective dose and for how long treatment should last. "There are many supplements that are suggested to support the immune system but few are studied to the degree that vitamin C, D, elderberry extract, probiotics and even echinacea have in some cases," says Jason Mitchell, ND, co-founder of "I would consider these to be the essential five immune-supporting items."


multivitamin supplement

If simplifying your life is your New Year's resolution, start by taking a multivitamin; it's a lot easier than trying to keep track of a handful of vitamin supplements to swallow every day. "Ideally one should take a personalized daily multivitamin which may contain doses of vitamin D, C, E and certain B vitamins that all help support ideal health on a year-round basis," says Dr. Levitan. She stresses that the exact makeup of the multi and the proper dosage will vary from person to person based on their diet, lifestyle, health concerns, gender, and age. "At times of particular concern, such as when ill or feeling stressed or run down, extra vitamin D, vitamin C, and zinc can be useful," she says. But, again, check with your physician before starting a new regimen of vitamin supplements. Otherwise, you could experience any of the 9 Dangers of Taking a Multivitamin Every Day, Say Experts.

Jeff Csatari
Jeff Csatari, a contributing writer for Eat This, Not That!, is responsible for editing Galvanized Media books and magazines and for advising journalism students through the Zinczenko New Media Center at Moravian University in Bethlehem, PA. Read more about Jeff