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Not enough data to know if Vitamin D should be used to treat or prevent COVID-19

by Cédric Ayisa - December 25, 2020   938 Views   6 min
Not enough data to know if Vitamin D should be used to treat or prevent COVID-19


There is not enough evidence to warrant using Vitamin D as prevention or treatment of COVID-19


Accurate as a whole (with reservations)

An article published by the University of Alberta in September 2020 claimed that there is not enough evidence to warrant using Vitamin D to treat COVID-19 patients. At the end of December 2020, we find this claim to still be accurate. However, we have reservations because the body of knowledge on this topic keeps expanding and some studies point towards a significant association, even if not a causation, between levels of Vitamin D and COVID-19 admissions and complications. 


Why we are fact-checking this claim

Since the beginning of the pandemic, we have seen many claims that Vitamin D is helpful in the prevention and treatment of COVID-19 – whether published in traditional media or circulating freely on social media. With the start of winter in the Northern Hemisphere, the conversation about whether Vitamin D treats and prevents COVID-19 is once again in full swing. It is also fuelled by several contradictory new studies and publications that are not based on clinical trials, and by the start of a new clinical trial that will only yield results several months from now. 


Why there are still not enough data to recommend Vitamin D as a treatment or prevention against COVID-19

Several studies and some recommendations stemming from these studies have been released (published or still in preprint) since the start of the pandemic, which is not surprising. However, the studies do not all agree that Vitamin D is helpful to prevent or treat COVID-19 – also not surprising. Participant samples have been generally small. And they are not studies based on randomised clinical trials, but rather, associations seen when analysing data from COVID-19 patients admitted to hospital. 

A larger study conducted of published sources and printed in the Journal Health Security on 14 December found an association between the prevalence of vitamin D deficiency, the risk of being infected with COVID-19, severity of the disease, and risk of dying from it in 46 countries. But association does not imply causation. An association can show a relationship between elements, but this does not mean that one causes the other: association does not imply causation, an assertion reiterated in the article from the University of Alberta. 

For instance, people with dark skin, who are obese, who are elderly or who are institutionalized are more likely to be vitamin D deficient and have other conditions such as hypertension and cardiovascular diseases. Several of these groups have also shown increased susceptibility to COVID-19. But the deficiency in Vitamin D has not been proven to cause the disease in these populations. 

meta analysis released in the UK’s Royal Society publishing on 1 December 2020 concludes that “evidence linking vitamin D deficiency with COVID-19 severity is circumstantial but considerable” and  recommends that “people admitted to hospital with COVID-19 should have their vitamin D status checked and/or supplemented and consideration should be given to testing high-dose calcifediol in the RECOVERY trial”. 

The most recent guidance on the use of Vitamin D for COVID-19 is the result of a review of all available evidence to date and was released on 17 December also in the UK, by the National Institute for Health and Care Excellence, UK (NICE), and is very explicit: “Do not offer a vitamin D supplement to people solely to prevent COVID-19, except as part of a clinical trial.”

At the moment, all eyes are on the clinical study that started in October 2020, funded by Bart’s Charity and conducted by Queen Mary University of London, in the United Kingdom. Results will not be available for several months, and while it will be tempting to generalise them to populations across the world, the participants of the study are all based in the UK. 

This is an important note because of the possible difference between the behaviour of Vitamin D in people living in countries where they may experience different exposure to sunlight. This is illustrated by the conclusions drawn from a double-blind, randomized, placebo-controlled trial involving 240 hospitalized patients with severe COVID-19 in Brazil from June to October 2020 (released in preprint), which showed that the administration of Vitamin D “did not reduce hospital length of stay or any other relevant outcomes vs placebo”.

As of 23 December 2020, Heath Canada reports two trials studying the effects of Vitamin D on COVID-19 in Canada, one in treating patients and the other in preventing COVID-19 among some health workers. 

All agree that further studies should be conducted. Consequently, all these reasons lead us to confirm the claim by the University of Alberta, that there is not enough evidence to warrant using Vitamin D as prevention or treatment of COVID-19 at this time. 


Why the conversation about Vitamin D is still going strong 

There are scientific, psychological, and financial reasons that keep the Vitamin D conversation going. During an emergency, preventative measures and treatments that have the potential to mitigate the effects of a disease should be discussed and studied appropriately. However, they should only be adopted when enough consistent and robust evidence has been accumulated. In the absence of these conditions, some treatments may be authorized for studies only, or for compassionate use and emergency use. 

In the case of Vitamin D, the main reasons for believing it has the potential to prevent or treat COVID-19 is because Vitamin boosts innate immunity in the lining of the lungs and may downregulate harmful inflammation. More studies are needed to find out, in controlled settings, whether administering Vitamin D to COVID-19 patients decreases the severity of the illness or the mortality rate. 

In addition to scientific reasons, the conversation about Vitamin D is still at the forefront because of psychological reasons. Since the beginning of the pandemic, we have consistently seen that when in doubt and under stress, many people believe information that is aligned with their beliefs rather than factual information – something called confirmation bias. There are many more psychological reasons why misinformation can be believed and spread, which you can find here. Even in the absence of evidence, some people would rather take the route of “it can’t hurt” – even if in the case of Vitamin D, it can hurt to self-prescribe larger quantities of Vitamin D. 

According to the article published by the University of Alberta, whose initial claim we find to be accurate, it’s always important to look at why some potential treatments are touted, as the Vitamin D market has become a multi-billion dollar market.


Why and when should we take Vitamin D?

Most experts and studies agree on one thing: the main role of vitamin D, in its hormonal form calcitriol, is to promote intestine, bone, and kidney health. Humans of all ages need to receive adequate intakes of calcium and vitamin D to maintain bone and joint health. Until our late twenties, this is used to build bone mass and after, it is used to maintain or prevent bone deterioration. 

Vitamin D in its hormonal form will interact with the VDR receptor found in activated T-cells. It can inhibit T helper cell proliferation and B cell immunoglobulin production. It assures that your T-cells are not over activated in an immune response. But its role in the immune system is still not well described. Finding an association of vitamin D and its effect on the immune system will require more research. So far, no evidence shows that vitamin D could have an effect in the prevention of COVID-19. More research is needed to determine the potential role that vitamin D and vitamin D deficiency may play in the prevention and treatment of COVID-19.

If you think that you have a vitamin D deficiency, consult your doctor to find out if a supplement may be appropriate for you and how you can take it. 

Our goal is to provide you with fact checks that are as accurate as and up-to-date as possible. If you think we've made an error or missed crucial information, please CONTACT US.


University of Alberta

There is not enough evidence to warrant using Vitamin D as prevention or treatment of COVID-19


Accurate as a whole (with reservations)

 December 25, 2020


Learn more about our fact-checking methodology HERE.

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