Published on February 3, 2021

Education on nutritional strategies to help improve immunity are lacking from the news and public health measures taken to end the COVID-19 pandemic

The news these days has been filled with talk about lock-downs, hygiene, social distancing, business and school closures, vaccinations and other measures being implemented to help stop or slow the spread of COVID-19. What is missing, however, are ways we can ensure or boost the integrity of our immune systems, to help shield us from infection if we are exposed and additionally improve our immune response if we are infected to minimize the risk of severe outcomes. Nutritional strategies are especially important, as both the innate and adaptive immune responses rely on certain nutrients in order to function properly – of note, vitamins D, A, C and minerals such as selenium and zinc. These approaches are particularly important because of the alarmingly high rates of insufficiency of these nutrients in the American population.

Nutrient Deficiencies Compromise Immune Function and Increase Infection Risk

From supporting the cells and tissues that create the physical barriers of the innate immune system (such as our mucous membranes) to having key roles in immune cell function and the regulation of inflammation, certain specific immune-relevant nutrients are so essential that a deficiency can have a negative impact and inhibit the body’s response to infection. Examples of several nutrients important to immune function are included in the infographic below.

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Many studies have linked nutrient deficiencies to an increased susceptibility to disease and worse disease outcomes, specifically those related to COVID-19. A new review by Uwe Grober and Michael Holick discusses several of these immune-relevant nutrients that “may help to increase the physiological resilience against COVID-19.” In other words, these nutrients play key roles in the body’s response to viral respiratory tract infections, including COVID-19, and may help protect against severe disease symptoms and outcomes.

Vitamin D

Much has been discussed about vitamin D and how it is involved in the immune response, along with evidence connecting higher vitamin D levels and intake with lower risk of COVID-19 infection, severe symptoms, and death. A summary of posts on vitamin D and COVID-19 can be found here.

Specific anti-SARS-CoV-2 properties of vitamin D include:

  • Supports the innate and acquired immune system
  • Increases the synthesis of antimicrobial and antiviral peptides (AMPs) that help lower the infectivity of respiratory viruses
  • Down regulates ACE-2 that SARS-CoV-2 binds to during the infection phase
  • Regulates the balance of T-cells
  • Increases lymphocytes, which are essential to the adaptive immune response
  • Has anti-inflammatory effects and helps prevent the cytokine storm
  • Increases the expression of antioxidant defenses
  • Increases the biodiversity of the gut microbiome, which has been shown to have protective effects against inflammation and respiratory tract infections
  • Produces vaso-protective effects (improves blood vessel integrity and function)

A panel of vitamin D researchers and scientists recommend a vitamin D level of 40-60 ng/ml (100-150 nmol/L) and over 200 doctors and scientists have openly advocated for vitamin D levels of 40-60 ng/ml to help fight COVID-19. Supplementation to reach these levels can vary greatly between individuals due to several factors, therefore testing is essential in order to calculate the appropriate supplement amount.

Vitamin A (Retinol)

Vitamin A is such an important nutrient to immune function that it has earned the name “the anti-infective vitamin.” Like vitamin D, vitamin A is a fat soluble vitamin that is converted within the body into a hormone-like molecule called retinoic acid (RA). Both work closely to influence immune cell function, especially within the adaptive immune response.

Specific anti-SARS-CoV-2 properties of vitamin A include:

  • Supports the innate and acquired immune system
  • Regulates T-cells
  • Increases lymphocytopoiesis, or the generation of new lymphocytes (T cells and B cells), that are essential to adaptive immunity
  • Has anti-oxidant and anti-inflammatory effects
  • Regulates surfactant protein gene expression, which may then reduce the impact of SARS-CoV-2 infection on the ability to breathe
  • Plays a crucial role in the formation of epithelial cells and improves the integrity of epithelial tissues (those of the respiratory, gastrointestinal and urogenital tracts)

An estimated 75% of adults in the United States do not meet the recommended intakes for vitamin A. The authors suggest 2,000 to 4,000 IU of vitamin A (as retinol) per day for all elderly, adults and adolescents in order to help prevent viral respiratory tract infections.

Vitamin C

Vitamin C is a popular immune-boosting nutrient that has been used for decades to help fight infections such as the flu and the common cold. One of the major roles of vitamin C is as an antioxidant, protecting cells of the immune system from damage due to oxidative stress that results from the response to infection.

Specific anti-SARS-CoV-2 properties of vitamin C include:

  • Supports the innate and acquired immune system
  • Has antiviral, antibacterial, antimicrobial and immunomodulatory properties
  • Decreases damage due to reactive oxygen species (ROS), necessary products of the immune response that fight infection, within the endothelium and alveolar membranes
  • Decreases the cytokine storm
  • Improves treatment to Acute Respiratory Distress Syndrome (ARDS)
  • Decreases the risk of multi-organ dysfunction
  • Increases immune cells such as lymphocytes, T-, B- and natural killer cells
  • Has anti-oxidant and anti-inflammatory effects
  • Enhances the integrity of epithelial tissues, especially within the alveolar system

For prevention, the authors suggest 1,000 to 3,000 mg of vitamin C per day, in divided doses, along with a quercetin supplement.


The element selenium has antioxidant, anti-inflammatory, immunomodulatory, anti-carcinogenic and antiviral properties. Selenium deficiency has been linked to increased risk of cancer, cardiovascular, thyroid, neurodegenerative and infectious diseases, as well as inflammation and immunodeficiency.

Specific anti-SARS-CoV-2 properties of selenium include:

  • Increasing GSH-peroxidases to decrease damage due to oxidative stress due to reactive oxygen species (ROS) that are necessary products of the immune response
  • Increases the synthesis of anti-viral proteins
  • Decreases inflammation
  • Supports the innate and acquired immune system
  • Regulates T-cell function
  • Increases the proliferation of T-lymphocytes
  • Has pronounced vaso-protective effects (improves blood vessel integrity and function)

The authors suggest 100-200 ug of selenium per day for elderly, adult, and adolescent individuals to help prevent viral respiratory tract infections, with a suggested serum level of 130-150 ug/L.


Zinc is a nutrient known to benefit the immune system, and deficiency of zinc impairs the capacity of many different immune cells to carry out their functions. Zinc has been shown to significantly reduce the duration and severity of the common cold, and to help prevent viral respiratory tract infections. Deficiency of zinc is common in the elderly, and subclinical zinc deficiency may be responsible for higher rates of infections and degenerative pathologies that are related to age.

Specific anti-SARS-CoV-2 properties of zinc include:

  • Supports the innate and acquired immune system
  • Regulates T-cell function and increases T-cell counts
  • Inhibits ACE-2 expression which SARS-CoV-2 binds to during the infection phase
  • Inhibits RNA-dependent RNA polymerase of viruses such as SARS-CoV-2; this impairs the ability of the virus to replicate and helps to reduce the risk, duration, and severity of infection
  • Has anti-inflammatory effects and decreases the risk of cytokine storm
  • Increases antioxidant defenses
  • Enhances mucosal barrier function (such as in the airway epithelium)
  • Has pronounced vaso-protective effects (improves blood vessel integrity and function)

The authors suggest 10-20 mg of zinc per day to help reduce the risk of viral respiratory tract infections.

Other Key Nutrients worth Noting

Nutrients work synergistically with each other, and the authors of this paper felt that several other immune-relevant nutrients deserved mention. These include amino acids (such as glutathione and glutamine), antioxidants (such as vitamin E), phytochemicals (such as quercetin), omega-3 fatty acids, and iron.

Could a Nutrient Deficiency be Compromising Your Immune Response?

Could getting more of certain nutrients help to decrease your levels of inflammation and improve your immune response? Find out by testing your vitamin D, omega-3s, magnesium and other essential elements (including copper and zinc), as well as your inflammation levels, with the Immune Boost home test kit offered by GrassrootsHealth, and get 10% off when you use coupon code BoostTen at checkout. Measuring levels is the only way to know if you are supporting your immune system and whether additional changes should be made, with supplementation, dietary changes, or both.

Are You Getting Enough Vitamin D & Other Immune Boosting Nutrients?

Everyone needs vitamin D! Below is a guide for how much you might need, and who may need more. Your levels can be tested safely at home – order your home test kit today.

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By joining the GrassrootsHealth projects, you are not only contributing valuable information to our study, but you are also gaining knowledge about how you could improve your own health through measuring and tracking your nutrient status, and educating yourself on how to improve it. Do you know what your status of vitamin D, omega-3s, and other essential nutrients is? Could your levels be improved? Test now to find out!

We now have a NEW GIFTING SERVICE that allows you to quickly send ‘Gift Cards’ to friends, family and coworkers who you consider might need immediate access to testing, and to Claim the Joy of Your Health TODAY. Give the gift today!

What does the Research Say about Vitamin D & COVID-19?

It’s TIME to start saving lives! If you can help PREVENT the majority of the death, it’s time! What’s it costing you/us not to take action NOW?

There is much published research that supports a clear link between vitamin D and COVID-19 showing that higher vitamin D levels are related to:

a decreased risk of testing positive for COVID-19

increased viral SARS-CoV-2 RNA clearance

better clinical outcomes among patients with COVID-19

less severe COVID-19 disease

decreased risk of death due to COVID-19

Be sure to educate yourself on the benefits and importance of vitamin D for immune health, and take steps to ensure you and your loved ones are getting enough.

You can review all of the COVID-19 and immune health information we have shared on this page.

How Can You Use this Information for YOUR Health?

Having and maintaining healthy vitamin D and other nutrient levels can help improve your health now and for your future. Measuring is the only way to make sure you are getting enough!

STEP 1 Order your at-home blood spot test kit to measure vitamin D and other nutrients of concern to you, such as omega-3s, magnesium, essential and toxic elements (zinc, copper, selenium, lead, cadmium, mercury); include hsCRP as a marker of inflammation or HbA1c for blood sugar health

STEP 2 Answer the online questionnaire as part of the GrassrootsHealth study

STEP 3 Using our educational materials and tools (such as our dose calculators), assess your results to determine if you are in your desired target range or if actions should be taken to get there

STEP 4 After 3-6 months of implementing your changes, re-test to see if you have achieved your target level(s)

Enroll in D*action and Build Your Custom Test Kit!