Vitamin D And Covid 19: What Do The Studies Say?

The Covid-19 viral infection quickly spread throughout the world, affecting millions of people. 

Even after a year of fighting against the virus, many people are still being infected. 

Over one million Covid-19 tests are performed every day in the United States.  And more than four million deaths have also been associated with the virus. 

Due to the impact of Covid, researchers are constantly looking at methods that may help to reduce the severity and incidence of the viral infection. 

Vitamin D and covid have become a topic of interest. An optimal vitamin D level has been linked to enhanced immune function, which may be useful when fighting against coronavirus. 

We take a closer look at the role that vitamin D may play in a Covid 19 infection. 

Vitamin D And Human Health

Vitamin D is a nutrient that is in certain foods. The body is also capable of producing this fat-soluble vitamin when the skin is exposed to the sun. The vitamin plays multiple roles in the human body. 

Several studies have been published to confirm the health benefits associated with a healthy vitamin D level in the body. In one study, researchers show that vitamin D may assist in reducing the risk of cardiovascular disease.

There are also studies that show the impact vitamin D has on the brain and mental health. When supplements containing vitamin D were given to a group of participants, researchers found a significant improvement in symptoms associated with depression

Vitamin D also plays a role in the well-being of both muscle tissue and bones. The vitamin is involved in the absorption of calcium, which is an essential mineral for bone development and maintenance. 

Additionally, it is also important to note the role that vitamin D plays in the immune system. The vitamin affects several cells that are part of the immune system. 

The vitamin is involved in both the adaptive and the innate responses of the immune system. 

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What’s The Connection Between Vitamin D And Covid?

Since vitamin D plays a role in both types of immune systems that exist in the body, many researchers have found an interest in determining a potential connection between the vitamin and Covid 19 infection

It is currently known that vitamin D is important for maintaining a strong immune system. Additionally, some studies also show vitamin D has the potential to exert anti-inflammatory effects. 

Research surrounding the potential antiviral properties of vitamin D is currently considered limited, however. A Covid 19 infection is caused by a type of virus known as the SARS-CoV-2. 

Research on this particular matter is somewhat limited. But it is important to note that some studies have suggested a positive association between vitamin D and other viral infections. 

In one study, researchers show that vitamin D could be a potential preventative option for influenza, a type of viral infection. The study also suggests that vitamin D may hold promising effects when used in a therapeutic treatment program for patients with influenza. 

What Do The Studies Say?

There are a few studies that have looked specifically at vitamin D and covid to better understand whether or not the use of vitamin D could help as both a preventative and a therapeutic agent in a covid 19 infection. 

One study showed a positive relationship between using a vitamin D supplement and the covid 19 virus. 

Researchers explain that there are multiple mechanisms by which vitamin D could reduce the severity of a covid 19 infection while also potentially reducing the risk of being infected. 

In particular, the study explains that vitamin D could help increase defensins and cathelicidins in the immune system. This may help to reduce the rate of replication in a current infection. 

Furthermore, vitamin D may help to reduce the release of cytokines that causes inflammatory responses during an active infection. This particular mechanism may be useful in reducing the severity of symptoms caused by the virus. 

In another study, researchers focused on determining the impact of vitamin D on the prognosis of a covid 19 infection. The researchers focused on previously published studies to better understand the effects that vitamin D may have. 

The researchers concluded that the vitamin D level status of a patient might be helpful when estimating three specific factors:

  • Risk of developing a covid 19 infection

  • Severity of the infection

  • Risk of death due to an infection from the virus

Researchers suggest that maintaining optimal vitamin D levels should be a critical factor in reducing the infection’s spread. Additionally, it is also advised that maintaining a normal level of the vitamin could contribute to a higher chance of survival. This, therefore, leads to a more positive prognosis. 


It is important to note that current evidence is mixed. Not all studies on vitamin D and covid provide positive results. This brings us to a study that was published in the PLOS MEDICINE journal. 

Researchers reviewed current evidence on the effects of vitamin D on the severity and susceptibility of covid 19. Researchers explain that several previous publications note an increased defense against the virus when vitamin D levels increase in the body. 

This was a two-sample study that focused on trials that included many participants, which would yield more accurate evidence. After analyzing reports and studies, the researchers concluded that there is currently no conclusive evidence. 

The researchers explain that the use of vitamin D supplements may not have the effects that some publications have previously reported, particularly based on genetic evidence. No conclusive evidence was found to suggest that increasing vitamin D levels through supplementation would reduce the risk that the general population would have for a covid 19 infection. 

Additionally, the researchers also note that the evidence does not show a reduction in covid 19 severity when vitamin D supplementation is provided to an infected patient. 

These findings make it difficult to determine the overall efficacy of vitamin D when aiming to improve the outcomes of patients infected with the virus. Researchers currently suggest that other therapeutic methods that may yield more effective results as preventative measures and treatment options for the covid 19 pandemic should be given priority. 

This, however, does not mean vitamin D should be overlooked. A deficiency of the nutrient can still result in serious adverse effects in the body while also weakening the immune system’s responses. 

RELATED: Some Vitamins Could Help Against COVID-19, Study Finds.


Current research on vitamin D and covid offer mixed results. In some studies, researchers found that a normal vitamin D level may assist in reducing the severity of a Covid 19 infection. Other studies, however, do not show any positive relation. 

It is still important to avoid a vitamin D deficiency. This can result in a weakened immune system, as well as several other adverse health effects. 

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  2. Aranow C. Vitamin D and the immune system. J Investig Med. 2011.
  3. [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006.
  4. Mousa A, Misso M, Teede H, Scragg R, de Courten B. Effect of vitamin D supplementation on inflammation: protocol for a systematic review. BMJ Open. 2016;6(4):e010804. Published 2016 Apr 5.
  5. Gruber-Bzura BM. Vitamin D and Influenza-Prevention or Therapy?. Int J Mol Sci. 2018;19(8):2419. Published 2018 Aug 16.
  6. Grant WB, Lahore H, McDonnell SL, Baggerly CA, French CB, Aliano JL, Bhattoa HP. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020 Apr.
  7. Yisak H, Ewunetei A, Kefale B, et al. Effects of Vitamin D on COVID-19 Infection and Prognosis: A Systematic Review. Risk Manag Healthc Policy. 2021;14:31-38. Published 2021 Jan 7.

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