Can vitamin D help prevent or treat COVID-19?

Crisitan Halati
November 25, 2020

In early October 2020, researchers from the Queen Mary University of London began a new clinical trial that aims to investigate whether supplementing with vitamin D can help prevent or treat COVID-19.

Named CORONAVIT, the trial is part of the larger COVIDENCE UK study that aims to investigate a wider range of COVID-19 risk factors.  

The CORONAVIT trial has been launched as a result of increasing evidence that a vitamin D deficiency may represent a significant risk factor for the disease. As such, the researchers will investigate whether correcting a vitamin D deficiency via supplementation can reduce the risk or severity of COVID-19.  

In this blog post, we will provide an overview of vitamin D’s role in health, explore the preliminary evidence that vitamin D deficiency is a risk factor for COVID-19, and discuss whether supplementation is a viable strategy for protection against it.

What is vitamin D?

Vitamin D is known as “the sunshine vitamin” because it is produced in the skin under exposure to sunlight. However, it can also be obtained from a variety of foods. Vitamin D has a wide range of roles in the human body, keeping bones, teeth and muscles healthy.  

It also supports the function of the brain, and is heavily involved in regulating the immune system, with vitamin D deficiency being a known risk factor for acute respiratory infections. These are infections that interfere with breathing, and include the common cold, pneumonia, and also COVID-19.

Is there a link between vitamin D deficiency and increased risks of COVID-19?

Preliminary research does indeed point towards such an association.  

Initial studies performed in this area observed that the death rates and geographical spread of COVID-19 across the world mirror areas with higher rates of vitamin D deficiencies in the population. Interestingly, researchers observed a 4.4% increase in mortality from COVID-19 for each 1 degree latitude north of the 28th parallel north. This association remained even when taking age into account.  

Scientists are investigating whether vitamin D deficiency is a risk factor for COVID-19

Furthermore, researchers also observed that the groups of people with the highest risk of serious COVID-19 and the groups of people that have a higher risk of vitamin D deficiency essentially overlap. These include:  

Additionally, as previously aforementioned, vitamin D plays a crucial role in regulating the immune system, and deficiencies impair the immune system. This is a known risk factor for acute respiratory infections and leaves people more susceptible to an array of infections, including COVID-19.  

Should I supplement with vitamin D to help prevent or treat COVID-19?

It must be noted that the research outlined above is preliminary and indirect but does provide a strong reason for further studies in this area.  

Alternative explanations exist, and for the first example given, it is also known that ultraviolet light also has effects on immunity that are vitamin D-independent. Furthermore, the overlap between the high COVID-19 risk groups and the high vitamin D deficiency groups can simply be explained by the fact that healthier people tend to lead healthier lifestyles, have better diets and spend more time outside- therefore having higher levels of vitamin D.  

This is noted by the NHS, which states that not enough evidence is yet available to support taking vitamin D to prevent or treat coronavirus.  

However, the NHS does recommend that all adults in the UK supplement with vitamin D between the months of October and March, when there is not enough strong sunlight for the body to make adequate levels of vitamin D.  

How much vitamin D should I take?

The NHS vitamin D recommendations are as follows:  

Vitamin D supplements can be found at most pharmacies and larger supermarkets in the form of tablets and drops. You may also see the dosage on the bottle written as “UI”. This stands for International Units, and 400 UI is equivalent to 10 micrograms of vitamin D.  

Vitamin D supplements are an easy way to achieve the daily intake recommended by the NHS

Vitamin D can also be obtained from food sources, though these are not likely to be sufficient to achieve the recommended NHS daily intake. These foods include:

For reference, 1 large egg contains roughly 43.5 IUs (1 microgam) of vitamin D, while 100 g of salmon contains 5.3 IUs (0.13 micrograms) of vitamin D, and 100 grams of steak contains 6 IUs (0.14 micrograms) of vitamin D.  

Overdoses of vitamin D are not likely, however the NHS recommends that adults and children aged 11-17 do not take more than 100 micrograms (4000 IU) per day. Similarly, children aged 1-10 should not take more than 50 micrograms (2000 IU) per day, and infants under 12 month old should not take more than 25 micrograms (1000 IU) a day.  

More information on vitamin D can be found here.  

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405052/
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7361294/
  3. https://www.qmul.ac.uk/media/news/2020/smd/clinical-trial-to-investigate-whether-vitamin-d-protects-against-covid-19.html
  4. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/



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