Published on October 9, 2020

How vitamin D helps to protect against SARS-CoV-2 infection and improve outcomes in those with active COVID-19

Vitamin D is used by every cell of the body, influences the expression of thousands of genes, and is involved in regulating over 80 biological pathways – importantly, vitamin D is a potent regulator of immune function. However, it may still be surprising how much one vitamin can influence the body’s response to a COVID-19 infection. Vitamin D deficiency has now been shown to increase susceptibility to COVID-19 and increase the risk that if you do have COVID-19, it will be severe enough to require hospitalization in the ICU and lead to death. Conversely, published studies have also shown reduced risk of severe symptoms and death due to COVID-19 with higher vitamin D levels (over 30 ng/mL). In fact, an analysis of over 190,000 Americans found that having a vitamin D level of at least 50 ng/ml resulted in a 53% lower positivity rate for SARS-CoV-2 infection than those with levels less than 20 ng/ml! The first-published randomized controlled trial on vitamin D and COVID-19 found that adding vitamin D to the standard treatment nearly eliminated ICU admissions and did eliminate deaths!

In Part 1 we reviewed how vitamin D acts to protect against COVID-19. Today we will describe how vitamin D influences the immune system in ways that are beneficial, such as preventing the hyper-inflammatory response characteristic of severe COVID-19 infection.

Vitamin D Regulates the Immune Response

Vitamin D plays a crucial role in regulating immune system activity – both innate and adaptive responses. As described in Part 1, vitamin D increases the innate immune response and may help reduce entry of SARS-CoV-2 into cells in the lung and reinforce the physical barriers, or junctions, between cells, which in turn may help prevent the spread of the virus between cells. Vitamin D also stimulates expansion of phagocytes (monocytes and macrophages) increasing their ability to fight off the virus by numbers. In addition, vitamin D directly stimulates phagocytes and lung cells to produce anti-viral proteins, cathelicidin and defensins, that kill the virus. However, an appropriate adaptive immune response is a vital part of the body’s defense against SARS-CoV-2. Vitamin D is a potent regulator of adaptive immunity, including both cell-mediated (T cell) and humoral (B cell) immunity. Vitamin D is needed by these white blood cells to help them recognize, bind to, and destroy SARS-CoV-2.

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What Causes A Severe SARS-CoV-2 Infection?

Once SARS-CoV-2 has been successful at replicating itself and spreading to surrounding cells, mild to moderate symptoms progress (e.g. sore throat, cough, fever and muscle aches) as part of a normal immune response to the virus. CD4+ and CD8+ T cell responses including secreted inflammatory cytokines are central to the successful elimination of COVID-19, as happens in most people.

However, in some people the immune response goes awry at this point and generates a hyper-inflammatory state referred to as the “cytokine storm” as depicted in the diagram below. The cytokine storm is the leading theory that explains why some people have a severe reaction to coronaviruses while others only experience mild symptoms. Moderate levels of inflammation are associated with mild-moderate symptoms of COVID-19, whereas the cytokine storm generates a hyper-inflammatory state associated with severe COVID-19 symptoms.

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The cytokine storm results from a sudden acute increase in circulating levels of different pro-inflammatory cytokines including IL-6, IL-1, TNF- a, and interferon produced mostly by T cells. These inflammatory cytokines, in addition to the ongoing replication and spread of the virus, trigger more immune cell involvement and tissue damage that leads to acute respiratory distress, multiple organ failure and possibly death. By dampening the cytokine storm, we can reduce the severity of symptoms and the risk of death.

Vitamin D Helps Control the Cytokine Storm and Reduce Symptom Severity

Vitamin D acts in many ways to regulate the adaptive immune response. Vitamin D stimulates CD4+ T cell proliferation and cytokine production, and antibody activity (B cells). Vitamin D acts to regulate T cell response through initiating dendritic cell tolerance. These dendritic cells in turn stimulate the increased production of T regulatory (Treg) cells and their production of anti-inflammatory interleukin (IL)-10, switching the response from being Th1-driven and pro-inflammatory to a Th2-driven anti-inflammatory response.

Vitamin D acts to suppress the production of inflammatory cytokines (such as IL-1, IL-6 and IFN which are predominant in the cytokine storm characteristic of severe COVID-19). Vitamin D also has an effect on the actions of B-cells and inhibits the production of antibodies. Overall, the immunomodulatory actions of vitamin D play a very important role in preventing the activation of an inappropriate hyper-inflammatory immune response.

Because the virus also binds ACE-2 receptors it interrupts the renin-angiotensin system, responsible for regulating blood volume, a pathway that is also regulated by vitamin D. Ensuring sufficient vitamin D may improve response to the virus in the lungs and lessen the impact of SARS-CoV-2 infection on reduced levels of surfactant (a liquid secretion that allows the lungs to open and fill with air) which may then reduce the impact of SARS-CoV-2 infection on the ability to breathe.

Thus, vitamin D is important to help regulate the immune response to a SARS-CoV-2 infection. Ensuring optimal levels of vitamin D is a safe and easy way to help support your immune response.

Do you know your vitamin D level?

Could a nutrient deficiency be putting a damper on your immune response? Find out by testing your vitamin D, omega-3s, magnesium and other essential elements (including selenium), as well as your inflammation levels, with the new Immune Boost home test kit offered by GrassrootsHealth. 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.

Enroll now with the Full Immune Boost Panel (which includes tests for vitamin D, Omega-3 Index, magnesium, zinc, selenium, copper, and hsCRP), and get 10% off when you use coupon code BoostTen at checkout.

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 – Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you’re interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!

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!