Can vitamin D cure Covid-19?

A new article has just been published in the Journal of Steroid Biochemistry and Molecular Biology looking to see if an oral vitamin D supplement can be used to cure covid-19. Considering that vitamin D is cheap, widely available, and safe, it would be pretty miraculous if that turned out to be the case.

The article describes a randomized controlled trial that was carried out in Spain earlier this year. The trial was open-label (i.e. both the patients and doctors knew who was in which treatment group) and involved 76 patients, of which 50 received 25-hydroxyvitamin D (a.k.a. calcifediol, the activated form of vitamin D) plus standard treatment, while 26 patients just received standard treatment (which at this point in time appears to have consisted mainly of Hydroxychloroquine and azithromycin, two drugs which have since fallen out of favor in the medical community).

Patients needed to fulfill three criteria in order to be accepted in to the study. They had to have a nasal swab PCR test positive for covid-19 and a lung x-ray showing an image consistent with viral pneumonia, and they also had to have at least moderate severity disease according to a scale that doctors use to grade pneumonia called CURB-65.

The patients in the treatment group received an oral capsule containing 0,532 mg of 25-hydroxyvitamin D on day one, followed up by capsules containing 0,266 mg on days three and seven, and thereafter weekly until discharge or admission in to the Intensive Care Unit (ICU). This is a monstrously high dose, enough to get people pretty much instantaneously up from a state of vitamin D deficiency to normal levels in the blood stream.

The patient groups varied a bit in terms of background factors. The control group was slightly sicker to begin with, with 62% having at least one bad prognostic factor, compared with 48% in the treatment group. Obviously this could have skewed the results in favor of vitamin D, since the people in the control group were more prone to have bad outcomes from the start. The overall difference in prognostic factors was due to a higher rate of high blood pressure (58% vs 24%) and a higher rate of diabetes (19% vs 6%) in the control group. The treatment group on the other hand had a larger proportion of participants who were immune suppressed (12% vs 4%).

So, what were the results?

Among the 26 participants who did not receive vitamin D, 13 were admitted to the ICU (50%), and two died (8%). Of the 50 participants who did receive vitamin D, only one individual (2%) was admitted to the ICU, and no-one died.

On the face of it, these results are pretty damn impressive! Vitamin D supplementation resulted in a 48% absolute reduction in risk of ICU admission, and a 100% relative reduction in risk of dying! If that isn’t an effective cure for covid-19, then I don’t know what is.

If these results held up in a larger, higher quality study, that would mean that you could pretty much cure the vast majority of people with covid-19 just by giving them a bolus dose of vitamin D. That would mean that we can pretty much stop researching a vaccine and just give every patient a bolus of vitamin D when they start to develop symptoms.

Of course, that is a pretty big if, as we will now discuss.

The first problem with this study is that it was small, which means that the confidence intervals are wide. For example, although 62% in the control group had at least one bad prognostic factor, compared with only 48% in the treatment group, which to me seems like a pretty big difference, that difference was not statistically significant. How can a difference that big not be statistically significant? Because only 76 people participated in the study. Now, the difference in terms of admission to the ICU was big enough to be highly statistically significant anyway, in spite of the small sample size, but there are other problems with the study.

The second problem is that the primary end point studied was admission to the ICU. Admission to the ICU isn’t a hard outcome like, say, death. It’s a decision made by a doctor about what the most appropriate level of care for a patient is. In general, doctors will place sicker patients in the ICU, and less sick patients will end up in a regular hospital ward, so ICU admission can be a proxy for more severe disease, but that doesn’t necessarily need to be the case. Considering that there wasn’t any blinding, and that the treating doctors knew exactly who was getting what treatment, it would be perfectly possible for the doctors to preferentially put people in the control group in to the ICU, just to make the results look better. Unethical? Yes definitely, but these things have happened. Can we say that happened in this study? No, but we can’t say that it didn’t happen either.

The third big problem is the lack of placebo. Apart from the fact that the doctors knew who was in which group, and might have acted differently towards different patients in ways that affected the results, the fact that the control group knew that they were the control group could also have messed up the results. Maybe the people getting vitamin D thought they would be cured from their covid-19, so they were, whereas the people who didn’t get vitamin D thought they would do badly, and so they did. One should never underestimate the power of the placebo effect to explain differences between groups.

Although there was a 100% reduction in mortality, the small size of the study means that we can’t really say anything about whether vitamin D affects mortality. It would have been enough for one person to die in the vitamin D group, and for one less person to die in the control group, for there not to have been any difference between the groups. That is giving random chance way to much influence over the results.

So, what can we conclude? Can an oral vitamin D supplement cure covid-19?

The results of this study are promising. In fact, they are very promising, and they are in line with earlier evidence that people who are vitamin D deficient get protection from respiratory infections if they take a daily vitamin D supplement.

However, this study reminds me a little too much of the first published trial of hydroxychloroquine as a treatment for covid-19. That trial also had significant flaws, and also showed significant benefit, but the results were not borne out by the bigger, higher quality trials that followed. This trial urgently needs to be followed up by bigger, higher quality double-blind randomized controlled trials that can corroborate the results.

In spite of my reservations, I do think it is reasonable for everyone to take a daily vitamin D supplement based on the results of this study. Vitamin D is after all safe, cheap, and widely available, so the potential benefits far outweigh the potential harms. Personally, I take 3,000 IU (75 ug) of vitamin D per day. If the results of supplementation are only half as good as they appear in this study, that would still be pretty incredible. Right now, vitamin D has a stronger evidence base when it comes to protecting against covid-19 than face masks do.

You might also be interested in my article about whether vitamin D protects against depression or my interview with Sky News about covid-19.

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Author: Sebastian Rushworth, M.D.

I am a practicing physician in Stockholm, Sweden. I studied medicine at Karolinska Institutet (home of the Nobel prize in medicine). My main interests are evidence based medicine, medical ethics, and medical history. Every day I get asked questions by my patients about health, diet, exercise, supplements, and medications. The purpose of this blog is to try to understand what the science says and to translate the science in to a format that non-scientists can understand.

20 thoughts on “Can vitamin D cure Covid-19?”

  1. If it works the question is why does vitamin D work? This study does not indicate vitamin D is a cure for COVID-19. Rather it indicates it has the ability to reduce mortality. The question is why? People die from the marked immune dysfunction induced by the virus known as cytokine storm. This is an autoimmune type reaction that is what a CAT5 hurricane is to a thunderstorm. The question is there a known mechanism to account for this? Possibly. Vitamin D is a hormone, not a vitamin. it is induced by sunlight. Sunlight affects immune function through several mechanisms. The fist is that vitamin D alters the inflammation response from TH17/TH1 (the hallmark of an autoimmune response) to a TH2 dominant response; it changes the M1 pro-inflammatory macrophage to the M2 anti-inflammatory macrophage. It keeps the dendritic reticulum cell in an immature, immuno-tolerant state. Sunlight activates cytotoxic T cell. Sunlight resists the circadian rhythm for optimal immune response. People who are vitamin D deficient are often sunlight deficient so it is difficult to know if it is vitamin D only or vitamin D plus sunlight. People who are sunlight deficient often are obese, lack exercise, have hyperglycemia and/or overt diabetes type 2.

    Since death is due to cytokine storm, the ability of vitamin to shift the immune response from autoimmunity to tolerance but just be enough to be clinically useful and shift the outcome.

  2. Thanks for this interesting and promising article. I actually take D3 plus K2 as it appears that D3 in higher doses washes Calcium out of the bones, but K2 fixes Calcium. Can you confirm this? Thanks again.

  3. Boy oh!! Actually it’s HCQ + ZINC
    (hydroxychloroquine + ZINC).

    HCQ opens up the zinc channels so that the zinc can enter the endoplasmic reticulum of the cells and stop the virus structures assembly – henceforth no more viral proliferation = RECOVERY

  4. Sebastian, we here in New Zealand, have to find a way out of the prison we have created for ourselves. We can’t wait for a vaccine. We will go broke waiting and our streets will end up being patrolled by Brownshirts.

    I note with interest what you say about drugs like HCQ. Can you comment on the use of these drugs for expediting the moving of zinc into cells etc?

    1. Hi,
      I’m not sure where the idea that hydroxychloroquine needs to be combined with zinc comes from. There are a few trials looking at the combination listed as ongoing at clinicaltrials.gov, but as far as I am aware there are as yet no published studies that look at the combination.

  5. Here is Alaska, most of us take vitamin D-3, as we have our periods of lack of sunlight. And–we have the best virus numbers in the US. Yes–we are isolated (we invented social distancing!), but I’m wondering if it is a coincidence?…

  6. As far as I’m aware from previous studies into vitamin D status and respiratory disease, the key is to have a good level in order to prevent infection or keep symptoms mild – rather than using it as a treatment. Admittedly it seems from the past few months of Covid that those with a D deficiency are more likely to have more severe illness and that therefore there can’t be any harm in raising their levels of vitamin D to an optimal point when symptoms have already appeared.

    However, what is equally interesting, or more so as a treatment for Covid, is how vitamin C is utilised by the body during a viral (or even bacterial) infection – but nobody wants to talk about that! It would appear that looking at those animals that produce their own vitamin C, unlike humans, they make huge amounts under normal circumstances (compared to our RDA) and even greater amounts when combating an infection. Makes sense to me.

  7. The combination of Hydroxychloroquine + zinc + azithromycin is something several doctors in the US have been using. Zinc is added to the mix as it has the effect of preventing viral replication the cells and the HCQ helps ‘push’ the zinc into the cells. It means that the strength of HCQ can be far lower, so that the adverse effects that were shown in the ‘false’ trial that halted its use in Covid are minimised. Also, as I understand it, HCQ doesn’t need to be taken constantly, at least when used as a preventative as it has a long half-life.

  8. Dear Dr. Rushworth,
    It is now 18th September as I write. We are consistently bombarded with stories that the “cases” are increasing all over Europe.
    It would be nice to hear from you again on what is happening in your hospital as regards true cases and deaths.
    Here in the UK we desperately need to get greater awareness of the Swedish experience.
    Best Wishes.

  9. Hej Sebastian,

    did you noticed the articles of Lorenz Borsche ?

    https://borsche.de/page/vitamind_sars?preferredlang=en
    https://borsche.de/page/vitamind_telepolis?preferredlang=en

    They were published in April/May 2020 and are very interesting.

    I personally supplement D3+K2+magnesia and zinc (7’000 i.U. Vitamin D3 in combination with Vitamin K2 mk7 alltrans).
    This is free of risks as long as one combines the D3 with K2 (and the co-factors magnesia and zinc).

    From the article about K2:
    “Attention heart and thrombosis patients: Old blood thinners (vitamin K antagonists for venous thrombosis, pulmonary embolism, atrial fibrillation, heart valve replacement and cardiomyopathies) e.g. phenprocoumon (Marcumar, falinthrome, phenpro) or warfarin (Coumadin) must be adjusted in consultation with the doctor when taking K2 under control of the Quick- but better INR values in the dosage, please read here beforehand. Modern anti-coagulants like Eliquis, … are not affected (main trade names in italics).”

    Especially old people have a lack of Vitamin D and more especially in a retirement home. This would also explain the high lethality.

    Feel free to contact Lorenz Borsche about this …

    Kind regards
    Carsten Budde

  10. Thank you for your comments about Vitamin D. Vitamin D deficiency is the real pandemic.

    Regarding HCQ, Dr. Zelenko stated that Randomized Control Trials of therapeutic regimens during a Pandemic are Immoral. You don’t test a new treatment protocol when the outcome for the placebo group is likely death. That would be like doing a double-blind RCT for parachutes: one group gets the parachute, the other gets a placebo parachute. If a therapeutic protocol is safe and thought to be beneficial, then all sick patients should have the choice to receive it.

    Many retrospective studies of using HCQ against COVID-19 missed the mark badly, either by administering toxic doses or evaluating only extremely sick patients, or both. HCQ + Zinc has been reported by practicing clinicians to be very effective when used early at the onset of symptoms. It prevents hospitalizations and ICU visits. Very hard to quantify something that didn’t happen. I will trust their field experiences and anecdotal evidence over petri-dish Phds sponsored by Big Pharma.

    Keep up the good work. New subscriber here.

  11. Hi, I would totally agree with the above, and I would urge you to do a whole article on HCQ+zinc. The so-called trials were set up by big pharma to fail. They had to discredit HCQ at all costs – it is too cheap, too effective and too safe. It must go! The only toxic thing about HCQ is its effect on big pharma profits. In the trials they deliberately used very ill, very sick, very elderly patients already in ICU, and gave them toxic doses of HCQ without zinc. And then they sat back and waited for the inevitable heart problems and death. This is criminal. Articles were written about these bogus trials, and published by prestigious medical journals. Then they were retracted when it was discovered they were dodgy as f,l but only after the alarming headlines had already gone all over the world. Here’s a great white paper on the topic – https://americasfrontlinedoctorsummit.com/wp-content/uploads/2020/09/White-Paper-on-HCQ-2020.2.pdf
    I read through the whole thing. It had me tearing my hair out. It was as if the author, Dr Simone Gold, was trying to convince people that cows like eating grass when we can all see that this is the case. To me, the politics surrounding HCQ or any aspect of the management of Covid 19 is of no consequence. This is, or should be, a health issue only.

  12. Surely you must have heard about Dr. Zelenko? (HCQ + zinc) – There’s a full story about it at Drbeen’s youtube channel from early sep.
    He describe it as the gun (HCQ) and the bullet (zinc)…. BANG!

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