by Nina Macaraig

COVID-19 and Vitamin D



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Probably the worst part of the current pandemic is the uncertainty and the lack of scientific knowledge verified by long-term research studies. In the face of the unprecedented Corona Virus Disease 2019 (in short, COVID-19), scientists and healthcare providers are learning as they go—or rather, race to come up with a cure and vaccine. What appears to be fact today may be proven invalid tomorrow. There's never been a better time to stick with what we know and support the body's immune system with a vitamin D supplement. 

There are a few things we all can do to keep ourselves healthy and safe and feeling somewhat in control. There are no miracle cures. Instead, good old-fashioned common sense—if you can, please stay at home to reduce risk of exposure—as well as the currently available scientific data suggest a road map for the rocky path ahead of us.[1]

One of the most crucial things you yourself can do in these uncertain times is to ensure that you get the proper nutrition to stay healthy and boost your immune system with vitamin D, so that it can cope with a potential infection in the appropriate manner.

Respiratory Infections and Vitamin D

One micronutrient, to which you should pay attention regardless of the current pandemic, has in fact piqued scientists’ interest for its potential to help combat acute respiratory infections, including influenza and the common cold—vitamin D. For example, a 2019 analysis (based on eight previous studies with a total of 21,000 participants) demonstrated that people with low Vitamin D levels are 64 percent more likely to contract pneumonia.[2]

An earlier analysis, dated 2015, was conducted by a consortium of 25 researchers at 21 institutions worldwide who collected and pooled these data about 11,000 study participants; it showed that study participants who already had a healthy baseline of vitamin D levels, but also took supplements reduced the risk of catching an acute respiratory infection by 10 percent. However, study participants who were vitamin-D-deficient managed to reduce this risk thanks to supplements by a whopping 50 percent.[3]

How does vitamin D accomplish such a feat?

Vitamin D boosts the levels of anti-microbial peptides and proteins (AMPs).[4] AMPs occur naturally in your body, for example, in the mucus produced by your nose and lungs. They serve as a first line of defense against anything that causes disease. They help to kill bacteria, fungi, viruses and even cancer cells. In effect, AMPs are your immune system’s own antibiotic medicine.

Acute Respiratory Distress Syndrome and Vitamin D

One aspect of COVID-19 most dangerous to otherwise perfectly healthy individuals consists of an over-reaction of the immune system. This over-reaction is known as “cytokine storm.”

In such a case, the body releases immune molecules called cytokines to fight infection and inflammation, but in such massive amounts that they cause a cascade of molecular and cellular reactions which damage organ tissue. When these cytokine-provoked reactions damage the lungs, Acute Respiratory Distress Syndrome (ARDS) occurs.[5]

But the distress does not remain limited to the lungs. As the heart, kidney and liver try to cope with the fallout in the form of an excessive workload and excess cellular waste from the lungs, they are also damaged. The resulting multi-organ failure is catastrophic and frequently leads to death. Vitamin D, however, helps to regulate the “on/off switch” of the immune system’s response, thus potentially protecting against this dangerous over-reaction.[6]

Vitamin D Deficiency and COVID-19

In April 2020, a group of Irish researchers published a preliminary report on the correlation between vitamin D deficiency and COVID-19 in older adults (aged 55+) in Ireland.[7] The table below incorporates some of the findings from the Irish Longitudinal Study on Ageing (TILDA) in summary form.



More likely to be

vitamin D deficient

More susceptible to COVID-19 with severe symptoms

Healthy adults (18-55)


(still, about 40% of US population, especially in northern states with fewer sunlight hours, are deficient)


Homebound people, especially older adults (55+)


due to lack of sunlight

and/or adequate food intake


People with chronic respiratory disease (e.g., asthma, emphysema)


yes, due to already existing damage to lung tissue



yes, due to already existing damage to lung tissue and suppressed immune system

People who are obese (BMI larger than 40)


usually due to lack of sunlight and/or appropriate vitamin intake


People with high blood pressure


(more research needed)


People who are immuno-compromised (e.g., cancer patients, patients with auto-immune diseases)


yes, due to weakened immune system


A researcher contributing to the study has stated: “…older adults have high levels of vitamin D deficiency which could have a significant negative impact on their immune response to infection. There is an even larger risk now of deficiency with those cocooning or confined indoors.”[8] The principal investigator of this study, Prof. Rose Anne Kenny of Trinity College, Dublin, Ireland, recommends: “Though we do not know specifically of the role of vitamin D in COVID infections, given its wider implications for improving immune responses […], those cocooning and other at-risk cohorts should ensure they have an adequate intake of vitamin D.”[9]

We at Health by Principle are very much aware that the scientific knowledge around COVID-19 continues to develop and change at a rapid speed, and so do the recommendations for reducing risks and taking preventive measures. Yet, we are also convinced that ensuring an appropriate intake of vitamin D[10]—whether through sunshine, food and/or supplements as approved by your healthcare provider—can only do good. Stay safe, be healthy!





[1] As for access to reliable, evidence-based scientific knowledge, we recommend that you consult the relevant pages on the websites of the Center for Disease Control and of the World Health Organization, as these institutions keep abreast of all research and update their information frequently.

[2] Y.F. Zhou, B.A. Luo, et al. “The association between Vitamin D deficiency and community-acquired pneumonia: A meta-analysis of observational studies,” Medicine 98, 2019, e1725.

[3] Adrian Martineau, David Jolliffe, et al. “Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data,” The British Medical Journal, 2017; i6583

[4] For more detail on AMPs, see Ling-Juan Zhang and Richard Gallo, “Primer: Antimicrobial Peptides,” Current Biology 26/1, 2016,

[5] Z. Xu, L. Shi, et al., “Pathological Findings of COVID-19 associated with acute respiratory distress syndrome,” The Lancet: Respiratory Medicine 2020. For a very clear, medical explanation of Acute Respiratory Distress Syndrome, see the lecture by Roger Seheult, MD, “How Coronavirus Kills: Acute Respiratory Distress Syndrome (ARDS) & COVID-19 Treatment,”

[6] Natascha Fitch, Allan B. Becker, and Kent T. Hay Glass, “Vitamin D [1,25(OH)2D3] Differentially Regulates Human Innate Cytokine Responses to Bacterial versus Viral Pattern Recognition Receptor Stimuli,” The Journal of Immunology, 2016, 196 (7): 2965-2972; doi:10.4049/jimmunol.1500460

[7] ; for a brief summary, see Catherine O’Mahoney, “Vitamin D could help fight off COVID-19,”

[8] Catherine O’Mahoney, “Vitamin D could help fight off COVID-19,”

[9] Catherine O’Mahoney, “Vitamin D could help fight off COVID-19,”

[10] The recommended daily average amount is 600 IU for healthy adults and 800 IU for older adults. According to the Institute of Medicine, adults should cap their Vitamin D intake at 4,000 IU. Allison Aubrey, “A bit more Vitamin D might help prevent colds and flu,”



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