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NMU 163 – Low Vitamin D Blood Levels Linked to More Severe Covid-19 Infections

Nutrition / Natural Medicine Update No 163 (May 14, 2020)

with Dr. James Meschino


Topic: Low Vitamin D Blood Levels Linked to More Severe Covid-19 Infections

Source: MedRxiv (April 2020) and the Irish Medical Journal (May 2020)


In recent Lifestyle Medicine Updates I have cited studies showing that for most respiratory tract infections, having low blood levels of vitamin D often leads to more severe and life-threatening outcomes, compared to those with more optimal blood vitamin D levels (above 80 nmol/L or 32 ng/ml). The first indication that the same holds true for the Covid-19 virus emerged in an April 2020 publication. Led by Northwestern University, the research team conducted a statistical analysis of data from hospitals and clinics across China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the United Kingdom (UK) and the United States. The researchers noted that patients from countries with high COVID-19 mortality rates, such as Italy, Spain, and the UK, had lower levels of vitamin D compared to patients in countries that were not as severely affected. Lead researcher Vadim Backman and his team chose to examine vitamin D levels after noticing unexplained differences in COVID-19 mortality rates from country to country. Some people hypothesized that differences in healthcare quality, age distributions in population, testing rates, or different strains of the coronavirus might be responsible. But Backman remained skeptical, stating, “None of these factors appears to play a significant role.” “The healthcare system in northern Italy is one of the best in the world. Differences in mortality exist even if one looks across the same age group. And, while the restrictions on testing do indeed vary, the disparities in mortality still exist even when we looked at countries or populations for which similar testing rates apply. “Instead, we saw a significant correlation with vitamin D deficiency,” he said.

How Might Vitamin D Deficiency Increase the Severity of Covid-19 Infection?

It’s really pretty simple. Vitamin D is required for the innate immune system to kill viruses, bacteria, and fungi on contact. These immune cells rely on vitamin D to make certain anti-septic chemicals that blow-up these pathogens before an infection can get started or get a lot of traction. However, if an infection does get started the body’s adaptive immune system starts to get involved, forming specific antibodies that can also destroy the virus. However, sometimes the adaptive immune system overreacts and starts oversecreting chemicals called cytokines, leading to a cytokine storm with accompanying organ failure, which is often the cause of death in these cases. In other words, the immune system’s cytokine storm is largely responsible for the life-threatening aspects of the virus, not the virus itself. So, it’s how the body’s immune system responds to the virus that appears to be a critical factor. As it turns out low vitamin D levels, not only decrease the ability of the innate immune system to synthesize chemical they need to destroy the virus on contact, but it also allows the adaptive immune system to overreact creating a cytokine storm. On the other hand, more optimal vitamin D levels are known to boost the function of the innate immune system to kill the virus on contact and to also tamp down the adaptive immune systems response, allowing it to generate necessary antibodies to fight the infection, but without producing a cytokine storm that leads to life-threatening outcomes. This may also explain why children are largely spared the life-threatening aspects of the virus, as they do not yet have a fully developed adaptive immune system, and thus, are less prone to a cytokine storm. Vitamin D cannot prevent you from contracting the virus, but it appears that you may be able to help your body respond to the presence of the virus in a way that makes it less life-threatening and debilitating. Of note is the fact that low vitamin D levels were also associated with poorer outcomes during the SARS epidemic (2003), which was also a coronavirus.

So, Who Is Most Prone to Low Blood Vitamin D Levels?

First, it is important to point out that older subjects, especially those over 80 years old, are in a high-risk category for vitamin D deficiency in many developed countries. I think it is also noteworthy to point out that darker-skinned individuals, who live in regions within developed countries that are above or below the 40th-degree latitude tend to have lower vitamin D blood levels. For most of us living in these regions, our blood vitamin D levels drop between October and May, as the wavelengths from the sun required to make vitamin D in our skin does not reach the earth during the winter months. However, the situation appears to be worse for darker-skinned individuals who often have lower vitamin D blood levels year-round. This is due to higher amounts of melanin pigment in the skin, which acts as a shield preventing UV-light from generating vitamin D synthesis in the skin of these individuals.

Overweight individuals, such as many type 2 diabetics, are also known to have low blood vitamin D levels. This is because vitamin D is a fat-soluble vitamin, and thus it gets stored in fat tissue. The more fat you have on your body, the more vitamin D you store in your fat cells, and thus, lower amounts circulate through the bloodstream. Overweight subjects also tend to secrete more inflammatory cytokines from their fat cells, known as adipokines, which also lower circulating vitamin D blood levels. As you know these sub-groups of people (as well as those other with other chronic inflammatory conditions, such as autoimmune disease patients) tend to have lower vitamin D levels and have been shown to be susceptible to more severe and more life-threatening coronavirus infections outcomes. Low blood levels of vitamin D may be one explanation as to why this is the case. We still have much more to learn about this virus and other coronaviruses, but in the meantime, it may wise to get your blood vitamin D level assessed by your doctor. If your blood vitamin D level is under 80nmol/L (32ng/ml), I suggest you discuss with your physician a prudent strategy to get it into the more ideal or optimal range.

The authors of a study published in the May 2020 issue of the Irish Medical Journal state the following,” the authors propose that, whereas optimizing vitamin D levels will certainly benefit bone and muscle health, the data suggests that it is also likely to reduce serious COVID-19 complications. This may be because vitamin D is important in the regulation and suppression of the inflammatory cytokine response, which causes the severe consequences of COVID-19 and ‘acute respiratory distress syndrome’ associated with ventilation and death”.

I have included the references for this information in the text below.


1. Ali Daneshkhah, Vasundhara Agrawal, Adam Eshein, Hariharan Subramanian, Hemant Kumar Roy, Vadim Backman. The Possible Role of Vitamin D in Suppressing Cytokine Storm and Associated Mortality in COVID-19 Patients. medRxiv, Posted April 30, 2020

2. Cytokine Storm and Covid-19 – The Lancet (April 27, 2020):

3. Quotes from the Lead Researcher Vadim Backman:

4. Laird E, Rhodes J, Kenny RA. Vitamin D and inflammation: Potential implications for the severity of Covid-19. Irish Medical Journal. 113;5:81 2020.



Eat Smart, Live Well, Look Great,

Dr. Meschino

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