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  • Writer's pictureDr. Lara

Vitamin D and COVID-19: The Science Simplified

For the last couple of years, the popularity of Vitamin D supplementation has risen as several research studies began showing strong associations between vitamin D deficiency and disease, including chronic heart failure, respiratory conditions, diabetes, hypertension, and colorectal cancer.

As the world was plagued with the SARS-COV-2 viral pandemic in 2020, the scientific community began an arduous quest to learn about the virus, its consequences and to find any evidence that could help minimize its spread, mortality rate, or at least, its symptoms. It was then noticed that individuals with severe symptoms and in need of hospitalization did not only share similarities in age and ethnicity, but also exhibited low levels of Vitamin D.

Is there a plausible explanation or is it purely coincidental?

While further research is needed (as with basically anything), there is strong evidence to suggest scientists may be on to something. However, science can get complicated and let’s be honest, we’ve had enough of that in the past year. So, let’s simplify!

Summary of Current Data

Before delving into the details of the mechanism of action of vitamin D, here’s a summary of the current scientific data as it relates to the virus:

  1. Decreased vitamin D is associated with increased mortality in hospitalized COVID-19 patients

  2. Decreased vitamin D is associated with increased ventilation requirements in COVID-19 patients

  3. Decrease vitamin D is associated with increased COVID-positive PCRs

  4. Decreased vitamin D is associated with increased CRP, fibrinogen, and D-dimer levels in COVID- 19 patients

  5. Decreased vitamin D is associated with decreased COVID-19 clearance from the body

  6. Decreased vitamin D associated with elderly, obesity, African Americans, Hispanics

  7. Decreased vitamin D is associated with increased risk of CHF, CAD, DM, and HTP

  8. Vitamin D has been shown to be effective against viral respiratory tract infections

As you may have noticed, these associations stem from “decreased Vitamin D”, meaning that individuals with insufficient or deficient levels when at the onset of contracting COVID-19 showed more exacerbated symptoms throughout. Why does this matter?

Because vitamin D supplementation in patients with deficiency/insufficiency after contracting the virus has not shown to help. Thus, taking vitamin D after getting COVID is unlikely to make much of a difference. It matters beforehand and it matters if you’re deficient. Prevention is key!

How can Vitamin D help lessen COVID-19 symptoms?

Vitamin D is a fat-soluble vitamin primarily involved in bone health. It helps to sequester calcium and deposit in the bones. But vitamin D also works as a hormone. In terms of immunity, it is transported to and activated by immune cells, such as macrophages. There, it makes two important protein peptides: B-defensins and Cathelicidins.


B-defensins, as you can deduce by their name, act as one of our defense mechanisms. Their job is to find viruses, such as SARS-COV-2 – also rhinovirus, influenza, RSV – and punch holes in their structure, thus destroying the virus.


Cathelicidins can act similarly to B-defensins and much more. They can not only cleave (phagocytosis) the viral peptides, they also basically tell your immune system where the virus is (chemotaxis) and increase your vascularity so macrophages can get there faster to fight it!

And that’s not all. These guys promote the transformation of naïve T-cells (think of an immune system cell that doesn’t know its function yet) into anti-inflammatory cells.

Now, imagine that you didn’t have enough circulating vitamin D in your bloodstream. What do you think would happen?

Hint: I’m sure you’ve heard this term circulating around, too. It is the cytokine storm!

When the naïve T-cell are not activated by Vitamin D to become an antigen to fight the virus, it goes on to release several cytokines in our bodies to indicate something is terribly wrong! Basically, this process results in a storm of cytokines that lead to a systemic state of inflammation targeting several organs, including the lungs, heart, liver, and kidneys. Aren’t these the organs commonly affected by COVID-19?

Not so coincidentally, these are also the common organs affected by vitamin D deficiency and/or insufficiency. Here's a short, overly simplified summary of how the cytokine storm and low vitamin D levels can do to organs:

Heart: leads to heart failure or already present heart failure; myocardial infarction (MI)

Lungs: induces acute respiratory distress syndrome (ARDS)

Kidneys: induces severe acute kidney injury (AKI)

Liver: triggers production of acute-phase reactive proteins (CRP, fibrinogen, ferritin) that further enhance the body’s inflammatory response

Arteries: the increased CRP leads to inflammation of blood vessels by the release of reactive oxidative species (ROS), increasing atherosclerotic plaques. This raises the risk of thrombosis (possible link to the high coagulability of COVID-19) and worsens symptoms congestive heart failure (CHF), hypertension, diabetes, and coronary artery disease (CAD)

How Can I Ensure I Have Enough Vitamin D?

The only way to truly confirm your vitamin D levels is to get a blood test.

However, doctors do not often order it unless you have a pertaining medical history or fall into one of the populations at risk for deficiency/insufficiency.

Low levels of vitamin D fall under 30 nmol/L.

The goal is to be around 60 nmol/L.

You could order at home tests on your own, which will cost you an average of $99 or through a qualified health practitioner. However, you may want to skip the costly test and invest in a quality vitamin D3 supplement regardless. Did you know 42% of Americans are deficient in this vitamin? And even if your levels are normal, supplementation is highly unlikely to lead to any side effects or toxicity, with its benefits (in addition to those aforementioned) outweighing the risks.

In addition to getting 15 minutes of direct sunlight daily, you may want to incorporate vitamin D-rich foods in your diet, such as:

- Mushrooms (D2)

- Egg yolk (D2)

- Liver (D2)

- Salmon (D2)

- Shrimp (D2)

- Sardines (D2)

- Fortified milk (D3)


There are several strong associations between low Vitamin D and COVID-19. Understanding them may help us be better equipped to fight the virus and hopefully decrease incidences and disparities in symptom severity and mortality rate. Although it will not stop the spread of the virus, vitamin D3 supplementation is likely to be a safe and relatively cheap method of preventing severe symptoms and decreasing mortality, especially for those at higher risk.

If you would like to learn more about vitamin D and whether supplementation is right for you, please contact me at and I’ll be glad to chat.

*It is important to consult with a qualified health practitioner to ensure the safety and adequate dosage before beginning any supplementation.

**The information in this article is meant to be purely educational and does not intend to treat or replace any treatment prescribed by physicians.


1. Feuer, Will. “CDC Quietly Adjusted Covid Death Data, Shows Higher Relative Toll on Black, Hispanic People.” CNBC, CNBC, 4 Dec. 2020,

2. Check out the Ninja Nerd! I based most of this content on his wonderful biochemistry lecture on COVID-19 and Vitamin D. It's a little over one hour long, but worth it if you're into that kind of stuff!

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