A Mayo Clinic Doctor’s Advice: Supplements to Stay Healthy During a Crisis


Supplements for immune system support

Research on the health benefits of dietary supplements is constantly progressing. Here's a roundup of dietary supplements that, according to the latest research, can help support your immune system.


If there was a super mineral, then zinc would be a contender. It's essential to your body's growth and development, wound healing, protein synthesis, and gene expression. If that's not enough, zinc helps regulate immune function, exhibits antioxidant activity, and helps support a balanced inflammatory response in your body.1 

Your immune system needs zinc to function properly. In fact, it seems that every immunological event is influenced by zinc, making the immune system especially susceptible to changes in zinc levels.

A deficiency of zinc can depress the body's immune responses. A zinc deficiency reduces your ability to eliminate pathogens, mount a response against threats, and produce antibodies.*2,3 One study in the elderly found that even a marginal zinc deficiency in this population adversely impacted immune function.4

Numerous studies illustrate how zinc benefits many health conditions.5,6 And there's evidence to support why individuals take a zinc lozenge or syrup when they feel a cold coming on.5-7 However, be very cautious of using intranasal zinc – it’s linked to a loss of the sense of smell, in some cases long-term or permanently.7 

Zinc is considered an essential nutrient, meaning your body can't produce or store it. Good sources of zinc include red meat, poultry, beans, nuts, certain types of seafood (crab, oysters, and lobster), whole grains, and dairy products. Oysters are by far the best source of zinc – with 32 milligrams in six medium-sized oysters. Don’t like oysters? You can always try a zinc supplement.

Vitamin D

Although best known for its role in maintaining healthy bones, recent research indicates that vitamin D plays an important role in supporting cardiovascular health and the health of the immune system.

Vitamin D enhances the function of immune cells, including T-cells and macrophages, which protect your body against invading pathogens.8 In a 2017 review of 25 clinical studies on vitamin D, a consortium of reviewers analyzed data collected from 11,000 adults. Reviewers found that daily or weekly supplementation of vitamin D2 or vitamin D3 reduced the risk of acquiring a respiratory tract health issue by about 12 percent. Supplementation was even more beneficial for individuals who were vitamin D deficient – reducing their risk by about 42 percent.9

Multiple studies have shown that a vitamin D deficiency can harm immune function and increase the risk of developing illnesses.10 It's estimated that approximately 40 percent of adults in the United States are deficient in vitamin D.11 

Vitamin D is a fat-soluble vitamin that is not found naturally in many foods, but is added to some foods like milk and cereal. It is found naturally in fatty fish such as salmon, mackerel, and sardines. Called the “sunshine vitamin,” your body also manufactures vitamin D when your skin is exposed to sunlight.

The sun’s ultraviolet B (UVB) rays interact with a protein called 7-DHC in the skin, converting it to vitamin D3. Vitamin D then goes through steps in the liver and kidneys for its final activation. Individuals who do not have access to sunshine, such as those living in northern latitudes, people who work at night and sleep during the day, darker-skinned individuals, or elderly shut-ins are particularly susceptible to low vitamin D levels. As you might imagine, vitamin D levels tend to be lowest at the end of winter.

Vitamin C

Although perhaps best known for its antioxidant properties, vitamin C (ascorbic acid) also supports your immune function.

Vitamin C accumulates in several types of cells in your immune system. These cells need vitamin C to perform their tasks.12 What's more, vitamin C levels in plasma and white blood cells rapidly decline during infections and when your body is stressed.13  

Additional research shows that being deficient in vitamin C results in a reduced resistance against certain pathogens, while a higher supply enhances several immune system functions.12  

Vitamin C is a water-soluble vitamin mainly found in fruits and vegetables. Unlike many animals, the human body can’t manufacture ascorbic acid, so your body’s vitamin C must be acquired from the food you eat or through supplements.


Curcumin, the primary active ingredient in turmeric, is a potent antioxidant.* There have been multiple studies on the relationship between curcumin, normal inflammatory responses, and the body's immune functions.14,15 

A recent review of research studying curcumin's effects on human health suggests that curcumin helps support a balanced inflammatory response throughout the body.

Studies show that curcumin blocks a biological process, called transcription factor NF-κB, that regulates a large array of genes involved in immune and inflammatory responses.* Any agent that beneficially impacts this regulatory process has the potential to provide support for individuals with several health conditions.*15 

The study also concluded that curcumin improves markers of oxidative stress.15 Oxidative stress is an imbalance of too many free radicals in relation to antioxidants in the body, which can lead to cell and tissue damage, including the lungs. In addition to loading up your curry or tikka masala with turmeric, you can also consider a curcumin supplement.


Astragalus refers to a genus of plants that has a long history in Traditional Chinese Medicine. And for good reason. 

Astragalus has plenty going for it in the realm of nutrition. It is a rich source of polysaccharides and flavonoids. Polysaccharides are vital to the body in that some help store the energy we get from food, while others help with cell structure. Flavonoids are powerful antioxidants with immune system benefits. In addition, Astragalus contains multiple trace minerals and amino acids.16 

One research study suggests that taking an oral Astragalus extract supports the immune system by increasing the activity level and number of immune cells.16 In most preparations, the root of the Astragalus plant is used to create a tea, liquid extract, or powder in a capsule.17 


Quercetin is an antioxidant flavonoid found in foods such as onions, berries, teas, and red wine. It is also found in several herbs, including American elderberry. 

The benefits of quercetin likely stem from its strong antioxidant activity.18 Research suggests that quercetin helps support a balanced inflammatory response in the respiratory tract, prevents damage caused by oxidative stress from illness, and helps prevent the release of histamine from a certain type of white blood cell called a mast cell.18  

Be smart about supplementation: Talk to your health-care professional first

Remember, all supplements – including all products labeled as "natural" – can have medication-like effects. Anything potent enough to produce a positive effect is also potent enough to carry risk. So before you take a new dietary supplement, talk to your health-care professional first. This is especially important if you take medications, have a chronic health problem, or are pregnant or breast-feeding. Brent Bauer, M.D.



An important note: No dietary supplement can diagnose, treat, cure or prevent any disease, including COVID-19. With the ongoing COVID-19 pandemic, it is especially important to understand that no dietary supplement, no diet, and no lifestyle modifications – other than the recommended social distancing and hygiene practices – can prevent you from being infected with the COVID-19 virus. No current research supports the use of any dietary supplement to protect you from being infected with the COVID-19 virus.


  1. Jarosz M, Olber M, Wyszogrodzka G, et al. Antioxidant . . . effects of zinc. Zinc-dependent NF-κB signaling. Inflammopharmacology 2017;25(1):11-24.
  2. Gammoh N, Rink L. Zinc . . . . Nutrients 2017 Jun 17;9(6). pii: E624..
  3. Hojyo S, Fukada T. Roles of zinc signaling in the immune system. J Immunol Res 2016;2016:6762343. 
  4. Haase H, Rink L. The immune system and the impact of zinc during aging. Immun Ageing 2009;6:9.
  5. Prasad A. Zinc: role in immunity [and] oxidative stress . . . . Curr Opin Clin Nutr Metab Care 2009;12(6):646-652.
  6. Zinc fact sheet. National Institutes of Health office of Dietary Supplements. https://ods.od.nih.gov/factsheets/zinc-consumer [Accessed April 1, 2020].
  7. Flu and colds: In depth. National Institutes of Health National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/flu-and-colds-in-depth [Accessed April 1, 2020].
  8. Rosa M, Malaguarnera M, Nicoletti F, Malaguarnera L. Vitamin D3: a helpful immune-modulator. Immunology2011;134(2):123-139.
  9. Martineau A, Joliffe D, Hooper R, et al. Vitamin D supplementation . . . : systematic review and meta-analysis of individual participant data. BMJ2017;356;i6583.
  10. Rondanelli A, Miccono A, Lamburgnini A, et al. . . . [T]he pivotal role of vitamin D, vitamin C, zinc, and Echinacea in three main immune interactive clusters (physical barriers, innate and adaptive immunity). Evid Based Complement Alternat Med 2018;2018:5813095. 
  11. Parva N, Tadepall S, Singh P, et al. Prevalence of vitamin D deficiency and associated risk factors in the U.S. population. Cureus2018 Jun;10(6):e2741. 
  12. Strohle A, Hahn A. Vitamin C and immune function. Med Monatsschr Pharm 2009;32(2):49-54.
  13.  Wintergerst E, Magini S, Hornig D. Immune-enhancing role of vitamin C and zinc effect on clinical conditions. Ann Nutr Metab 2006;50(2):85-94.
  14. Flu and colds: In depth. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/flu-and-colds-in-depth [Accessed March 31, 2020]
  15. Hewlings S, Kalman D. Curcumin: A review of its effects on human health. Foods 2017;6(10):92.
  16. Roxas M, Jurenka J. Colds and influenza: A review of diagnosis and conventional, botanical, and nutritional considerations. Altern Med Rev 2007;12(1):25-48.
  17. Astragalus. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/astragalus [Accessed March 31, 2020]
  18. Quercetin. Natural Medicines Database. https://naturalmedicines.therapeuticresearch.com/ [Accessed March 31, 2020]

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