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Vitamin D role in alleviating the burden of COVID-19 pandemic

The COVID-19 pandemic is undeniably the most challenging global health crisis ever faced since World War II. The virus has spread to every continent (except Antarctica) and cases are on daily rise. Countries worldwide are extensively working to mitigate and halt the infection spread through broad testing, quarantining citizens, carrying out contact tracing and enforcing precaution policies strictly.

Currently, there is no treatment or vaccine that can lessen the number of cases or related mortality. Therefore, prophylactic measures such as staying safe and enhancing the defensive mechanisms of our immunity systems are only what we can rely on to fight this catastrophic viral infection. Scientists have been highlighting that COVID-19 morbidity and mortality are correlated with vitamin D deficiency. During the Spanish flu (1918-1920), scientists have also suggested potential association between vitamin D and the case-fatality rate in that pandemic.

COVID-19 pattern across different European countries

Despite the high performance healthcare systems in Italy and Spain, they reported high mortality rate (28.3% and 34.6% respectively) compared to other European countries. Upon analyzing these two populations specifically to illustrate patterns, it was found that the reported average of 25-hydroxyvitamin D concentration (biologically active form of vitamin D in blood) is as low as 19.9 ng/mL in Italy and 22.5 ng/mL in Spain. Also France, a country that is notable to have the most severe vitamin D deficiency cases, reported one of the highest COVID-19 mortality rates. On the other hand, Scandinavian countries that own the lowest rates of vitamin D deficiencies, did not report high COVID-19 morbidity and/or mortality. Nordic nations are not sunny as France, Italy and Spain; yet, this drove them to consciously rely and highly consume vitamin D supplementation to avoid being deficient.

Factors that alter 25-hydroxyvitamin D concentration

There are number of factors that negatively affect 25-hydroxyvitamin D concentration. Age is one of them; where 25-hydroxyvitamin D is inversely related to age. This might explain why the elderly are more susceptible to COVID-19 severe morbidity and mortality. Another reciprocal factor is the intake of some medications such as antibiotics, antihypertensives, antineoplastics, anti-inflammatory agents, endocrine drugs, antiepileptics and antiretrovirals. The use of such medications also increases with age; hereby, another explanation why aged population has been the most vulnerable as such. Moreover, individuals who have chronic conditions (such as chronic obstructive pulmonary diseases, pneumonia and hypertension) exhibit low levels of 25-hydroxyvitamin D compared to healthy ones. Furthermore, seasonally level of vitamin D decreases in winter due to less exposure to the sun.

Vitamin D mechanisms in alleviating the severity of COVID-19

Vitamin D plays a major role in improving the clinical outcomes of COVID-19 patients. Generally, viral infections trigger cytokine storm (where body attacks its own cells rather than just fighting the virus), which can only be fought back by innate and adaptive immunity. Unlike ibuprofen which suppresses the innate immunity and consequently worsen the COVID-19 treatment; vitamin D boosts the innate immunity, in order to decrease the viral load. Moreover, vitamin D acts as a moderator of adaptive immunity and inhibits inflammatory processes. Thus, it effectively influences both innate and adaptive immunity. As vitamin D effectively suppresses the cytokine storm triggered by COVID-19 viral infection; chances of having severe COVID-19 cases are decreased and related complications are bypassed.

Additionally, it is revealed that Vitamin D has a vital role in regulating c-reactive protein level, which consequently reduces the risk of infections and cardiovascular diseases. A study showed that severe deficiency of vitamin D is associated with 1.4 higher risk of high c-reactive protein production; which subsequently rises the risk to have COVID-19 severe cases. Nevertheless, supplying with vitamin D may obstruct damage to the body, hence decreasing the frequent production of c-reactive protein. The study calculated the risk of severe COVID-19 cases to be potentially reduced by 15.6% if vitamin D is indeficient.

On another note, Vitamin D spares vitamin C usage by enhancing the expression of antioxidation-related genes; thus, supporting an antimicrobial function. Many reviews suggest that vitamin D decreases the risk of developing influenza and microbial infections (including gram positive and gram-negative bacteria, enveloped and non-enveloped viruses and fungi) as well as related mortality. A dose of 4000 IU/d Vitamin D supplement is capable of reducing the risk of viral infections. Another study showed that a dose of 2000 IU/d was effective in reducing the risk of upper respiratory conditions in postmenopausal women. A high dose as 500,000 IU/d in ventilated intensive care patients was effective in reducing hospitalization length, increasing hemoglobin concentration, improving blood ability to carry oxygen and enhancing iron metabolism.

“Prevention is the daughter of intelligence” Walter Raleigh

In a nutshell, Vitamin D proved to be plausible as prophylaxis contributing to reduced severity of COVID-19 illness. This is even more crucial in the times of “lockdown”, where exposure to sunlight is almost close null. Vitamin D supplementation can be considered an accessible affordable primary prevention regimen in such a time of an ambiguous pandemic. Individuals should seek raising their 25-hydroxyvitamin D concentration to 30ng/mL and above through vitamin D supplementation. Fortified basic food with vitamin D (such as dairy and flour products) can add up few ng/mL. It is also highly recommended to provide healthcare workers and patients in hospitals with vitamin D during the COVID-19 pandemic, as it halts hospital-acquired infections and COVID-19 spread. Other micronutrients that support the immune system includes magnesium, zinc and vitamin C.


Daneshkhah, A., Eshein, A, Subramanian, H, Roy, H. & Backman, V. (2020). The role of vitamin D in
suppressing cytokine storm in covid-19 patients and associated mortality. Medrxiv

Grant, W., Lahore, H., McDonnell, S., Baggerly, C., French, C., Aliano, J. & Bhattoa, H. (2020).
Evidence that vitamin D supplementation could reduce risk of influenza and covid-19 infections and death, Nutrients, 12, 988