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Vitamin D and COVID-19

In this series of articles, medical students from across the country will discuss a range of topics from medical ethics to the NHS to public health to medical conditions to clinical governance.


Around 1 in 5 adults in the UK are more vulnerable to COVID-19. Why?

In Davao Del Sur, Philippines, giving Vitamin D supplements to COVID-19 patients increased the chance of them showing mild symptoms instead of extreme ones by around 20 times. A study in Illinois concluded that Vitamin D deficient people were twice as likely to test positive for COVID-19. A study in Boston University concluded that people with sufficient vitamin D levels in the United States had as much as a 54% reduced risk of getting infected with COVID-19. These studies point to the fact that Vitamin D supplementation could hold promise as a preventive agent for COVID-19.

What is Vitamin D?

Vitamin D or Calciferol is an important vitamin that we can produce in our own body. The vitamin can be synthesized in our skin when sunlight (or any light source containing UV-B rays in the range 290-310nm wavelength) strikes our skin. It is possible to synthesize a sufficient amount of Vitamin D if we spend enough time outdoors or in the sun. However, with an increasingly developed world and a mostly 'indoor' lifestyle, more often than not we find ourselves deficient in Vitamin D. Since Vitamin D is needed for calcium and phosphorus reabsorption, it is necessary for strong bones, teeth and development. A deficiency, therefore, results in symptoms including fatigue, bone fragility, teeth weakening and skeletal deformities. However, Vitamin D does more than just make our bones strong.

Vitamin D strengthens our innate immune system which reduces COVID-19 incidence and transmission by extension. Our innate immune system is made up of certain 'fighter cells' - macrophages, monocytes and dendritic cells to name a few. All of these cells have Vitamin D receptors on them, where Vitamin D works to enhance or increase the efficiency of these cells in killing any germs - not just SARS-CoV-2 (the virus that causes COVID-19).

How does Vitamin D help us fight COVID-19?

When talking about COVID-19 specifically, the virus attaches itself to the ACE-2 receptor which is specifically found on the cells of our respiratory and gastrointestinal tracts. That's why COVID-19 results in symptoms involving those systems. ACE-2 receptors work together with ACE receptors. ACE causes the constriction (narrowing) of our capillaries while ACE-2 does the opposite. Together, they work to balance our blood pressure. SARS-CoV-2, and in fact all coronaviruses, attack our ACE-2 receptors which eventually results in pulmonary vasoconstriction which reduces lung function and capacity. In experiments conducted on rats, doses of Vitamin D resulted in an increase in the number of ACE-2 receptors.

Apart from this, severe cases of COVID-19 often involve our 'fighter cells' to attack our body cells - known as the 'cytokine storm'. Our immune system goes into overdrive and excessive or uncontrolled levels of cytokines are released. This then activates more immune cells, resulting in hyper-inflammation which can seriously harm or even kill the patient. Vitamin D increases the production of anti-inflammatory cytokines such as Interleukin 4 and down regulates inflammatory cytokines such as Interleukin 2.

How affordable is this treatment?

Vitamin D deficiency is extremely common - over 50% of Americans and around 20% of British adults - making large amounts of the population more vulnerable to COVID-19. However, this high demand for Vitamin D supplements and Vitamin D fortified products has resulted in manufacturers devising cheaper and more efficient ways to produce their goods. For less than £1, Vitamin D supplements can be an affordable, widespread and accessible treatment for COVID-19 - effectively preventing its spread.


  • Vitamin D is produced in our body, but can also be obtained from supplements and Vitamin D fortified products such as milk.

  • Vitamin D strengthens our immune system.

  • COVID-19 attacks ACE-2 receptors and Vitamin D is known to increase the number of ACE-2 receptors in mice.

  • Vitamin D prevents cytokine storms by increasing the production of anti-inflammatory cytokines.

Further Reading


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