Supplements, Immunity, and COVID-19: The Facts To Know

The ongoing battle against COVID-19 has brought on stress and many unknowns. While we have learned lots of information about this virus since the start of the pandemic, there are still some uncertainties. Currently, the best line of defense against COVID-19 is to get vaccinated once eligible, and to use other prevention strategies such as wearing a mask and social distancing. But is there anything else we can do to help boost our immune systems to keep from getting COVID, or to lessen the severity of our symptoms?

Many places on the internet and social media are talking about supplements and COVID-19. What’s true? What isn’t? We know that certain supplements have immunity-boosting properties, and while they may not be able to prevent COVID-19, they may be able to give our immune systems a little extra support during the pandemic. Here, we will walk you through the research-backed facts we know about certain vitamins, minerals, the immune system, and how it all relates to COVID-19 so far.

  1. Vitamin C
    • How It Works~ Vitamin C supports certain cell functions in our body that help to boost our immunity. One example of this is that vitamin C builds up in phagocytes. Phagocytes are cells that consume foreign particles that could harm our health (you can think of these cells as little vacuum cleaners). The buildup of vitamin C in these cells helps to strengthen the cells’ ability to destroy microbes. This is just one of the many ways vitamin C acts to support our immunity. In a 2017 article on how vitamin C impacts immunity, Anitra C. Carr and Silvia Maggini note that “supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections.” While we do not have any research that vitamin C supplementation can prevent the sars-cov-19 respiratory virus, we can still upgrade our immune systems with a little extra vitamin C. If you’re already sick with COVID or another kind of bug, your body may need some extra vitamin C due to increased metabolic needs and inflammation.
    • Am I Getting Enough?~ The recommended amount of vitamin C for adults is 75-90mg each day. Not getting enough vitamin C may weaken your immune system and make you more likely to contract infection. Can we get too much? Well, yes; too much vitamin C might not cause significant problems, but you could experience unpleasant symptoms such as nausea, abdominal pain, or diarrhea.
    • Where Do I Find Vitamin C?~ Lucky for us, there are plenty of foods we can get vitamin C from. The majority of these are within the fruit and vegetable groups. Oranges, grapefruit, kiwi, and strawberries are some fruits that offer lots of vitamin C. Bell peppers, broccoli, Brussel sprouts, tomatoes, and other vegetables are great sources of vitamin C as well.
    • What About COVID-19?~ There isn’t enough research yet to support or deny vitamin C supplementation for COVID-19 prevention or treatment. Researchers recommend investigating the effect of vitamin C supplementation on COVID-19 treatment though, as it has proven to be helpful for our immune system in many other ways.
  2. Vitamin D
    • How It Works~ Vitamin D is largely known for its contributions to our bone health, but we’ve been learning that it plays important roles in our immunity, too. In her article on vitamin D and immune health, Cynthia Aranow, MD, teaches us that the immune cells in our bodies carry vitamin D receptors, which may allow vitamin D to influence and regulate our bodies’ immune responses. Some other ways vitamin D helps our immunity is by lowering the rates at which viruses replicate in our bodies, and by reducing inflammation.
    • Am I Getting Enough?~ The recommended amount of vitamin D for adults is 15-20 mcg each day. Some signs of vitamin D deficiency can include bone tingling, pain, and fatigue, and it’s correlated with increased risk of infection. Vitamin D also helps with the absorption of calcium, so if we take in too much vitamin D (also known as toxicity), we will experience a buildup of calcium in our blood. This can result in nausea, vomiting, weakness, and frequent urination.
    • Where Do I Find Vitamin D?~ Some of the greatest sources of vitamin D include fatty fish like cod, trout, and salmon. Fortified cereals and milks (dairy or plant-based) are also good sources of vitamin D. And don’t forget to get some sunshine so that your body can make its own vitamin D!
    • What About COVID-19?~ Like with vitamin C, there isn’t enough research yet to support or deny vitamin D supplementation for COVID-19 prevention or treatment. Researchers are actively looking into this though, since past research suggests that vitamin D supplementation may help prevent respiratory tract infections.
  3. Magnesium
    • How It Works~ Magnesium helps our immune system by improving our white blood cells’ ability to find and destroy microbes. Its antithrombic and bronchodilation effects have led to the suggestion that magnesium supplementation may be able to help in the treatment of respiratory disorders. Magnesium also activates vitamin D in the body, which we know has its own important roles in supporting our immune system.
    • Am I Getting Enough?~ The recommendation for adult women is about 30-320 mg/day, and 400-420 mg/day for men. Symptoms of magnesium deficiency include nausea, vomiting, weakness and fatigue, poor appetite, and other symptoms. Toxicity symptoms can also include nausea and vomiting, as well as diarrhea, muscle weakness, depression, abnormal heartbeat, and other symptoms.
    • Where Do I Find Magnesium?~ We can get magnesium naturally from foods like nuts and seeds, nut butter, dark leafy greens, beans and legumes, whole grains and fortified cereals, fish, poultry, and beef. This gives us a good amount of variety to meet magnesium needs!
    • What About COVID-19?~ There’s still research being done to determine if magnesium supplementation can help prevent or treat COVID-19, but experts in the cardiology field – James DiNicolantonio, PharmD, and James O’Keefe, MD – recently wrote a paper together that suggests the supplementation of magnesium and vitamin D together may be helpful for anyone battling the coronavirus. Their article can be found here.
  4. Zinc
    • How It Works~ Zinc is a key player in a number of functions supporting immunity. Thymus and bone marrow are the sites of immune cell maturation in the body, but these organs can’t function without zinc. Zinc supports frontline cells in our body by making them more resistant to infection, and thus keeping harmful bacteria and viruses out. It helps to make sure that our white blood cells detecting and consuming these pathogens are working their best. Zinc is also a necessary component for our sense of taste and smell.
    • Am I Getting Enough?~ The recommendation for adult women is about 8 mg/day, and 11 mg/day for men. Signs of zinc deficiency can include diarrhea, taste changes, and hair loss. Zinc deficiency also impairs the production of lymphocytes (white blood cells that play active roles in the immune system), and increases risk of viral infection and respiratory disease. While deficiency is more common than toxicity, it is possible to experience nausea, vomiting, upper abdominal pain, and fatigue with excessive intake of zinc.
    • Where Do I Find Zinc?~ The food sources richest in zinc include shellfish (specifically oysters, crab, and lobster), and beef. Beans, nuts, pork, poultry, dairy, whole grains and fortified cereals are other good sources, too.
    • What About COVID-19?~ Researchers believe that adequate zinc consumption could possibly reduce the risk of contracting the coronavirus, or reduce its severity; however, there isn’t enough research to support zinc supplementation for COVID-19 prevention or treatment still.
  5. Omega-3’s
    • How It Works~ Omega-3’s have been studied for their effects on our immune cells. One of the effects outlined in an article by Saray Gutiérrez, Sara L Svahn, and Maria E Johansson is that the mediators made by omega-3 fatty acids increase phagocytosis (the consumption of microbes and debris in the body by cells) in certain white blood cells. These mediators also help to regulate the immune cells in our bodies. This happens when the omega-3 mediators compete with omega-6 mediators, which promote inflammation and vasoconstriction more than omega-3’s do. When our concentrations of omega-3’s are greater than those of omega-6’s, less inflammation is promoted in the body.
    • Am I Getting Enough?~ An adequate daily intake of omega-3’s for adults is outlined as 1.1 g/day for women, and 1.6 g/day for men. If you’re experiencing dry, scaly skin, or dermatitis, check with your doctor to see if you are experiencing deficiency of either omega-3 or omega-6 fatty acids. It’s considered safe to take up to 5,000 mg/day of omega-3’s, but if you notice any unwanted side effects, you should decrease your intake. If you take fish oil as an omega-3 supplement, you can experience some signs of toxicity if you take too much. Symptoms include high blood sugar, increased risk of bleeding, diarrhea, insomnia, or stroke. Additionally, fish oil supplements that contain vitamin A may contribute to a vitamin A toxicity, too.
    • Where Do I Find Omega-3’s?~ As mentioned above, fish oil is a popular omega-3 supplement. But what foods offer us omega-3’s? Our primary sources include fatty fish (like salmon, herring, and mackerel), nuts and seeds (flaxseed, chia seeds, walnuts), and canola oil.
    • What About COVID-19?~ There isn’t any research yet to support or deny omega-3 supplementation for COVID-19 prevention or treatment.
  6. Probiotics
    • How It Works~ You may have heard about the many benefits of probiotics on our gut health, but did you know that probiotics can help support our immune system, too? Some of the potential functions of probiotics include strengthening the gut barrier, supporting phagocytosis by white blood cells, and suppressing viruses’ ability to replicate in the body. Researchers are still unclear though on how exactly these processes work.
    • Am I Getting Enough?~ Unlike vitamins and minerals, probiotics aren’t a nutrient required by the body to function – they are bacteria! Because of this, there aren’t any specific recommendations for if the average healthy person should or should not take a probiotic supplement. If you have any questions about the use of probiotics and if it would benefit you, talk with your primary doctor or registered dietitian.
    • Where Do I Find Probiotics?~ Probiotics are live microorganisms that can be consumed to promote gut health (side note- these are different from prebiotics, which is essentially food for the probiotics you consume). We can get probiotics naturally from yogurts, certain cheeses, and fermented foods kombucha, kimchi, pickles, sauerkraut, and miso.
    • What About COVID-19?~ While the research is still insufficient to recommend the prevention or treatment of COVID-19 with probiotic supplementation, there are some promising studies. Prior to the coronavirus pandemic, studies were done to look at the ability of probiotics to help prevent and treat respiratory tract infections. The results showed benefits of probiotics in some outcomes, but not all. Based on the previous studies done, researchers think that probiotic supplementation could be a helpful facilitating therapy for COVID-19 treatment. In a study in Italy, probiotic supplementation showed significant reduction of certain COVID-19 symptoms compared to others not provided with the supplementation (the placebo group). The supplemented group also showed reduced risk of being transferred to the ICU, and experiencing respiratory failure and/or mortality. More studies are expected to be done so that we can learn more!

The verdict from the National Institutes of Health (NIH) Office of Dietary Supplements is that “data are insufficient to support recommendations for or against the use of any vitamin, mineral, herb, or other botanical, fatty acid, or other dietary supplement ingredient to prevent or treat COVID-19.” While research is exciting and may look promising so far, it is not enough to guarantee the prevention or treatment of this virus. Continue to follow your local guidelines and recommendations from the CDC and your healthcare providers to make the best choices for your own health.

Want to know if dietary supplements would benefit you? Schedule an appointment with one of our registered dietitians for personalized recommendations that meet your needs. Tips:

  • Check that it’s right for you. Some supplements can interact with medications, so you may want to talk with your doctor or registered dietitian before starting a new supplement. If you are taking other supplements already, you’ll also want to check to make sure you aren’t putting yourself at risk of toxicity.
  • Look for USP verification. Supplements are not regulated by the FDA the same way that medications are. To ensure that the supplement you’re choosing contains exactly what its container says (and no contaminants), choose a supplement with a USP Verified seal on the bottle. To learn more about USP verification, read here.
  • Data is insufficient. Remember that the is currently no cure for COVID-19. Researchers are working and supplements are not guaranteed to prevent or treat COVID-19.


Anderson’s Nutrition, LLC does not endorse or make any recommendations for the use of or against supplementation, and is not connected to any of the sources referenced in this article.

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