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Vitamin D and COVID-19

Written by
Dr. Divya Banu M
and medically reviewed by Dr. Nasir

Published on Dec 26, 2020 and last reviewed on Sep 08, 2022   -  6 min read


Did you know COVID-19 patients with vitamin D deficiency are twice as likely to have severe complications, including death? Read the article to learn more.

Vitamin D and COVID-19


COVID-19, the known pandemic, has been affecting many lives with its upcoming new variants. Even when most people are fully vaccinated worldwide and now getting booster doses. The common symptoms of COVID-19 are cough, headache, cold, respiratory distress, etc. COVID-19 can be transmitted via cough droplets, aerosols from the mouth, sneezing, etc. This infection also leads to major pathologies like pneumonia, myocarditis, cytokine storms, etc. The preventive measures include getting fully vaccinated, getting booster dose if eligible, and all these have the mechanism of inflammation. The most common tests that are being carried out are rapid antigen tests and RT-PCR., wearing masks, frequent hand sanitization, maintaining personal hygiene, social distancing, quarantine when required, and having a well-balanced diet filled with nutrients and hydration.

The world is still experiencing the ill effects of COVID-19 pandemic and its impacts. At the pandemic’s beginning, people needed to quarantine and change their lifestyle habits like diet modifications, exercise, and work from home. All these modifications are associated with less time spent outside thus less sun exposure and reduced production of vitamin D in body. The National Institute of Allergy and Infectious Diseases' director earlier mentioned that these immune-boosting products were not scientifically proven. Although such a statement was made, vitamin D, known as the sunshine vitamin, is a multifunctional hormone that regulates the adaptive and innate immune responses of the body. Before, the National Institute of Health (NIH) did put forward that there is not sufficient evidence to prove the effectiveness of vitamin D in preventing COVID-19 as the research was going on about this topic.

Vitamin D is a fat-soluble nutrient that is available in 2 forms: D3-Cholecalciferol and D2-Calciferol. The major sources are fatty fish, fish liver, egg yolk, liver oil, sunlight, etc. The daily recommended doses are 400 IU of cholecalciferol (In countries with good sunlight like India, RDA is 200 IU per day). Active form (Calcitriol) promotes bone resorption and mineralization and intestinal calcium and phosphorus absorption.

Preterm babies not exposed to sunlight and babies of mothers with severe deficiency and fat malabsorption are prone to develop deficiency. In preterm babies, the deficiency manifests as early as eight weeks of age, leading to rickets. In adults, it is called osteomalacia. Low levels of Vitamin D have been shown to enhance inflammation and thus, may increase the risk of pneumonia and upper respiratory tract infections due to the virus. Also, low vitamin D levels can lead to thrombotic events. The treatment is six lakhs IU of Vitamin D oral or IM. Hypervitaminosis may lead to GI (gastrointestinal) upset, hypotonia, polyuria, polydipsia, hypercalcemia, hypercalciuria, and metastatic calcification.

How Is Vitamin D Deficiency Connected To COVID-19?

Various studies are being done to assess the benefits of vitamin D in preventing COVID-19.

In May 2021, the National Center for Biotechnology Information has stated in a study that there is an association between Vitamin D deficiency and the severity of COVID-19 illness. Reduction in the RT-PCR positivity, levels of D-dimer, CRP, and the number of affected lung segments were seen in people with an increased level of vitamin D. A study conducted by Northwestern University in the U.S. showed that COVID-19 patients who had severe vitamin D deficiency are twice as likely to have severe complications, including death.

Some studies have shown that vitamin D can reduce the risk of developing respiratory tract infections, excluding COVID-19. Some controversial research has also shown that vitamin D deficiency may increase the risk of developing coronavirus infection and also the severity of COVID-19. Also, a group of researchers in Italy have found an increased risk of mortality in COVID-19 patients who were given vitamin D supplementation.

Some other nutrients are also being tested for association with COVID-19 and include zinc, vitamin C, etc.

Vitamin D And Heart Health In COVID-19:

There are various sequelae of COVID-19 when spoken about the cardiovascular or heart system like a heart attack or myocardial infarction, acute cor pulmonale, cardiogenic shock, etc. Some studies show that vitamin D may prevent atherosclerosis, a major culprit in various cardiac pathologies. There is no direct evidence about the benefits of vitamin D in COVID-19 related heart diseases, and previous studies promise possibilities of the same.

Vitamin D And Lungs In COVID-19:

Various pulmonary functions and infections are being seen in this pandemic era. Martineau et al. have mentioned the effects of vitamin D supplements in preventing acute respiratory infections.

Vitamin D and the Nervous System:

Vitamin D restrains the depletion of neural perception in COVID‑19 patients by provoking the expression of neurotrophins. Few people affected by COVID-19 have neurological symptoms like loss of taste and smell and headaches. Some studies show ARS-CoV-2's presence in the brain's neurons and may prove that the coronavirus targets the nervous system through the olfactory bulb. SARS-CoV-2 can undermine nerve cells, especially neurons in the nervous system leading to neurological symptoms in COVID-19.

Vitamin D stimulates nerve growth factor, neurotrophin-3, glial neurotrophic factor, and Schwann cells. Vitamin D has been reported to promote the outflow and disparity of oligodendrocyte progenitors and reinforce the remyelination of neurons to improve neurotransmission. There are current medical trials of vitamin D to preclude and cure neurological diseases by making use of neuroprotective effects. Scientists believe that vitamin D improves anosmia-like symptoms and restrain neurological complications in COVID-19.

Vitamin D Act as an Immunosuppressant in COVID‑19:

Localized synthesis of Calcitriol is progressively acknowledged compared to systemic production as it is in charge of vitamin D's immune effects in respiratory diseases. At the commencement of inaccurate inflammation, vitamin D suppresses T1 and T17 cell expansion and their abnormal cytokine release. At the resolving stage of inflammation, the distinctness of T2 cells mediated by vitamin D and the release of their cytokines are essential to prevent organ damage.

Another important mechanism is the overexpression of pro-inflammatory cytokines, where vitamin D utilizes its immunotherapeutic effects in pulmonary infection. Vitamin D treatment structurally can decrease mRNA expression and interferon-stimulated genes in respiratory syncytial virus (RSV). Vitamin D reduces the manifestation of interleukin 6 through the p38 mitogen-activated protein kinases signaling pathway. Interleukin 6 plays a pivotal role in the cytokine storm. In patients infected with SARS-CoV-2 pneumonia, interleukin-6 correlates with significant negative outcomes and lowers the natural killer cell numbers. Anti-interleukin 6 treatment is in a clinical trial for severe respiratory failure in COVID-19. There are sustained clinical trials of vitamin D prophylaxis and autoimmune disease management by utilizing its strong immune-suppressing function. Considering that vitamin D is a robust immune-suppressing supplement, it suppresses the unusual immune response and cytokine storm in COVID-19.

Prevalence of Vitamin D Deficiency:

It is believed that 50 % of the population has skimpy vitamin D status. Encapsulation of vitamin D decreases the skin's ability with age. Hyperpigmentation of the skin reduces the performance of UV-B to induce the encapsulation of vitamin D. It is noted that people who live far away from the equator have diminished vitamin D levels. The vitamin D standard is less with darker-skinned people. The ascendancy of vitamin D insufficiency is utmost in:

  • Older adults (61 %).

  • Overweight individuals (35 %).

  • Hospitalized patients (50 % to 60 %).

  • Severe hyperpigmentation in the skin (40 %).

Should You Take Vitamin D Supplements

There are some questions that should be addressed before coming to a conclusion. They are as follows:

1. Do all the COVID-19 hospitalized patients have less vitamin D levels?

2. Did supplementation with vitamin D increase the levels of chemical mediators of inflammation like Tregs?

If satisfactory answers are available for these questions based on scientific studies, it can confidently be justified to use vitamin D supplementation in COVID-19 patients or to prevent COVID-19. Also, since this vitamin is a sunshine vitamin, the prevalence of COVID-19 or its severity should be reduced in people in such a geographical area where there is adequate sunlight.

Hence, even though it is a controversial topic, the consumption of Vitamin D has shown benefits with innate and adaptive immunity. Also, it has been found in a recent study that vitamin D supplementation has reduced the risk of hospitalization in patients affected with COVID-19. As it is difficult to get enough vitamin D from food sources alone, it is advisable to consume supplements. Still, it is always advisable to consult your physician before consuming the same.

Taking more than the recommended dose can prove to be toxic. Hence, it should be taken under the strict supervision of a physician. Some studies have reported that the effect of vitamin D supplementation in preventing acute respiratory distress syndrome or respiratory tract infections was much better when it was taken in low doses for a long time rather than increased amounts taken for a short period. Along with vitamin D, Zinc can also be consumed in case of having cold symptoms.


The number of COVID-19 cases diagnosed and recovered continues to rise with each new SARS-CoV-2 variant, although slowing in summer and fall due to beneficial effects of sunlight. Vitamins and minerals have always been a good source for increasing immunity in the body. The functions of vitamin D in bone and calcium metabolism are well-known; however, this pandemic has reinforced its immunomodulatory effects. Vitamin D is related to the severity and mortality of COVID-19 cases, a high prevalence of vitamin D deficiency was seen in patients with COVID-19 with acute respiratory failure. Although research is still being done on the benefits of vitamin D in COVID-19, there are some positive possibilities depending on some studies done. Anything taken without a physician's guidance in such a situation can prove toxic.Therefore, making a medical consultation is mandatory before consuming the same. Online medical platforms have made this consultation process easy.

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Last reviewed at:
08 Sep 2022  -  6 min read




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