Do higher vitamin D levels prevent severe COVID-19 infections?

Does your blood level of vitamin D affect your risk of a severe case of COVID-19? If so, what should you do? And if raising vitamin D levels reduces the risk of COVID-19, why haven’t public health policymakers talked more about it?

I can answer the first two questions, but to answer the third question, you’ll need to understand that those policymakers are motivated by something other than public health.

The Public Library of Science (PLoS) just published another study, reinforcing the importance of vitamin D in relation to COVID-19.

The authors concluded, “Among hospitalized COVID-19 patients, pre-infection deficiency of vitamin D was associated with increased disease severity and mortality.”

Does this mean that low vitamin D levels cause severe COVID-19 infections? No. Does the study show that raising vitamin D levels protects you from COVID-19? Not necessarily, but based on other research, such an assumption would be a pretty safe bet.

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The majority of people on the planet have vitamin D levels well-below optimal, but those with deficient levels of vitamin D are at a much greater risk of numerous health problems. The table blow shows some of them.

Health Problems Associated with Low Vitamin D Levels
Flu and respiratory infectionsInsulin resistance and diabetes
Heart diseaseOsteoporosis and bone fractures
Lower IQs of babiesAtopic dermatitis
CancerDecreased adrenal hormones
Decreased strengthIncreased body fat
Low birth weight of newbornsMultiple sclerosis
PsoriasisRheumatoid arthritis
SchizophreniaType I diabetes

As it relates to infections, low vitamin D levels have been consistently associated with higher risks of flu and respiratory infections. Again, we’re talking about association, not causation.

However, raising vitamin D levels through supplementation reduces the risk of the flu and respiratory infections, as well. Clinical research shows that vitamin D supplementation supports immune function.

I wrote the following in a previous blog post:

In one study, supplementing with 2000 IU of cholecalciferol has been shown to lessen the occurrence of cold and flu symptoms.

In another study published in 2010, children in Japan took 1200 IU of cholecalciferol or a placebo from December 2008 through March 2009. At the end of the study, 18.6% of the placebo group and 10.8% of the vitamin D group got the flu.

That’s a 42% reduction, using an amount that still isn’t enough to reach optimal levels in most people.

Interestingly, the CDC found that flu shot was only effective in 23% of people who got it based on 2014 data.

Vitamin D: Deficiency Symptoms And Benefits Of Supplementation

Vitamin D and COVID-19

Multiple studies now show that low vitamin D levels are associated with more severe COVID-19 infections. To remain objective, though, you have to keep in mind that low-vitamin D levels are associated with other factors that are associated with a greater risk of COVID-19 infections.

Aging, obesity, poor nutrition, and a lack of outdoor activity raise the risk of COVID-19 infection by themselves, while also increasing the likelihood that an individual is deficient in vitamin D.

A study published in JAMA in September of 2020 (yes, a year and a half ago) showed that low vitamin D levels were associated with a 77% increased risk of a COVID-19 infection.

Prior to that, a July 2020 study of 14,000 people showed “low plasma 25(OH)D levels appear to be an independent risk factor for COVID-19 infection and hospitalization.”

A November 2020 study determined the following:

Vitamin D level is markedly low in severe COVID-19 patients. Inflammatory response is high in vitamin D deficient COVID-19 patients. This all translates into increased mortality in vitamin D deficient COVID-19 patients. As per the flexible approach in the current COVID-19 pandemic authors recommend mass administration of vitamin D supplements to population at risk for COVID-19.

Jain A, et al.

Early research on COVID-19 and vitamin D was handicapped by a consistent flaw. Patients had their vitamin D levels tested while they were infected with COVID-19. Without knowing what their levels had been in the past, researchers couldn’t confidently say that low vitamin D levels led to worse COVID-19 outcomes, or that COVID-19 infections led to low vitamin D levels.

That’s where the most resent study comes in.

Dror AA, et al. put together a study that included patients’ vitamin D levels prior to COVID-19 infection. Then, they looked at how the virus affected people at varying levels upon infection. Not surprisingly, those with prior vitamin D deficiency were far more likely to get a severe case of COVID-19 and to die.

In the authors’ words:

While 48.1% of vitamin D deficient (<20 ngmL) patients (pre-infection 25(OH)D level) had severe disease courses, less than 10% of patients with vitamin D levels 20 ngmL had severe courses. While the mortality of patients who had 25(OH)D vitamin D levels 20 ngmL was 5% or lower, the mortality of vitamin D deficient patients (<20 ngmL) was much higher, at 25.6%.

Dror AA, et al.

In essence, vitamin D deficiency quintupled the risk of severe COVID-19 infection and death. For those who understand how vitamin D affects the immune system, this isn’t a surprise.

Vitamin D strengthens innate immunity, so it might be expected to decrease COVID-19 infection and transmission. Vitamin D also affects metabolism of zinc, which decreases replication of coronaviruses.

Meltzer DO, et al.

Innate immunity is your body’s first line of defense against all pathogens. It includes the barriers created by your skin and mucous, as well as immune system cells that attack any pathogens that get by them. If you read my article on quercetin (Quercetin and COVID: Results of two recent studies), you’ll remember that quercetin helps shuttle zinc into cells. Vitamin D affects zinc metabolism. And zinc, then, helps reduce viral replication. If a virus can’t replicate, it cannot continue infecting you.

Follow the Money

There’s little to no money to be made in marketing vitamin D. It’s inexpensive and easily accessible. Maybe that’s why you’ve never heard President Biden mention it. Anthony Fauci might have said something about it once or twice.

Instead of recommending something with an extremely impressive safety record and compelling research to back up its preventative effects, they keep pushing vaccines, which do not stop the spread, nor keep people from getting infected. And, they carry numerous known and unknown risks.

Even more appalling is that the Biden administration plans to spend $30 million on needles and crack pipes to make drug usage “safer and more equitable.” Imagine the impact they’d have if they gave out $30 million worth of vitamin D to American citizens!

It’s sad that the people in charge of our public health won’t promote that which helps the public maintain health.

I’ll wrap this up with a quote from one more paper. This was published in May of 2020 in the British Journal of Nutrition. It sums up well the importance of vitamin D.

Although vitamin D was primarily recognised for bone metabolism, increasing evidence indicates its proper function for nearly every tissue in the body including brain, heart, lung, muscle, immune system and skin. Therefore, the treatment of vitamin D deficiency would be vital for several diseases including cardiovascular and neurological disorders, cancers, autoimmune diseases and infections as well. Likewise, a recent review recommended that in people at risk of influenza COVID-19 infection, 250 μgd of vitamin D3 for a few weeks (or a month), that is, to rapidly increase the 25(OH)D concentrations and then 125 μgd in the follow-up can be considered. The target should be to raise its value above 40–60 ngml. Additionally, the authors also suggested higher vitamin D3 doses for infected patients with COVID-19.

Kara M, et al.

I posed an important question with the title of this blog post: Do higher vitamin D levels prevent severe COVID-19 infections? The answer is obvious, even if it remains absent from the recommendations of politicians, public health policy makers, and the mainstream media.

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Dror, Amiel A., et al. “Pre-Infection 25-Hydroxyvitamin D3 Levels and Association with Severity of COVID-19 Illness.” PLOS ONE, vol. 17, no. 2, Feb. 2022, p. e0263069. PLoS Journals,

Information, National Center for Biotechnology, et al. “The Innate and Adaptive Immune Systems.” InformedHealth.Org [Internet], Institute for Quality and Efficiency in Health Care (IQWiG), 2020.,

Jain, Anshul, et al. “Analysis of Vitamin D Level among Asymptomatic and Critically Ill COVID-19 Patients and Its Correlation with Inflammatory Markers.” Scientific Reports, vol. 10, no. 1, 1, Nov. 2020, p. 20191.,

Kara, Murat, et al. “‘Scientific Strabismus’ or Two Related Pandemics: Coronavirus Disease and Vitamin D Deficiency.” British Journal of Nutrition, vol. 124, no. 7, Oct. 2020, pp. 736–41. Cambridge University Press,

Meltzer, David O., et al. “Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results.” JAMA Network Open, vol. 3, no. 9, Sept. 2020, p. e2019722. Silverchair,

Merzon, Eugene, et al. “Low Plasma 25(OH) Vitamin D Level Is Associated with Increased Risk of COVID-19 Infection: An Israeli Population-Based Study.” The FEBS Journal, vol. 287, no. 17, 2020, pp. 3693–702. Wiley Online Library,