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Vitamin D and COVID-19

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Vitamin D and COVID-19

6 min read


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

Medically reviewed by

Dr. Mohammed Abdul Nasir

Published At December 26, 2020
Reviewed AtFebruary 27, 2024


COVID-19, the known pandemic, has been affecting many lives with its upcoming new variants. 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., and all these have the mechanism of inflammation. The most common tests that are being carried out are rapid antigen tests and RT-PCR. The preventive measures include getting fully vaccinated, getting a booster dose if eligible, 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 the 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 working from home. All these modifications are associated with less time spent outside, thus less sun exposure and reduced production of vitamin D in the body. The director of the National Institute of Allergy and Infectious Diseases mentioned that the 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 body’s adaptive and innate immune responses. Before, the National Institute of Health (NIH) put forward that there was not sufficient evidence to prove the effectiveness of vitamin D in preventing COVID-19 as research was going on about this topic.

Vitamin D is a fat-soluble nutrient 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, the RDA is 200 IU per day). The active form, Calcitriol, promotes bone resorption, bone 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 (intramuscular). 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 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 found an increased mortality risk in COVID-19 patients who were given vitamin D supplementation. Some other nutrients are also being tested for association with COVID-19 including 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 seen in this pandemic era. Martineau et al. has 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 SARS-CoV'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 using neuroprotective effects. Scientists believe vitamin D improves anosmia-like symptoms and restrains 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 systemic production is responsible for 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. Since 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 low 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?

Some questions should be addressed before concluding. They are as follows:

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

2. Did supplementation with vitamin D increases 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 a geographical area with adequate sunlight.

Hence, even though it is controversial, the consumption of Vitamin D has shown benefits to 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 by 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 report 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 cold symptoms.

Vitamin D supplementation and COVID-19 Vaccine Response:

Individuals with compromised immunity have decreased vaccine response, and vitamin D can further worsen the condition. However, vitamin D can potentially strengthen immune responses and modulate them. Hence, a study was conducted in the United States to assess the impact of vitamin D supplementation on the COVID-19 vaccine response. The study was a randomized clinical trial where one group received vitamin D supplements, and the other group was not provided with any supplements. Blood tests were taken at three intervals with 28 days gap, and the antibody and vitamin levels were measured with immunological fluorescence. It was understood that coronavirus requires vaccination for its prevention because of its faster transmission rate. Studies have concluded that the nutritional value of individuals influences their immune systems. Also, during the initial days of COVID-19, the exact treatment was not identified. Patients were administered vitamin D, B, and C supplements because the common condition noticed was vitamin deficiencies. Thus, there is a pathogenetic relationship between COVID-19 and vitamin D.


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 the 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.

To know more about this topic, consult a physician or specialist online.

Frequently Asked Questions


Is It Possible to Combine Zinc and Vitamin D for Intake?

Both vitamin D and zinc are essential for good health. For instance, vitamin D regulates physiological functions like blood pressure and cell proliferation, while zinc protects the reproductive system. Although zinc and vitamin D do not directly interact, they are connected in several ways because they have complementary effects on many bodily functions. Therefore, incorporating both nutrients into the diet will benefit the individuals.


How Does One Strengthen Their Immune System After Recovering From COVID?

- Always maintain a balanced diet.
- Have a good sleep pattern.
- Drink lots of water.
- Regular exercise.
- Practicing breathing exercises and meditation.
- Staying away from alcohol, smoking, and other bad habits.
- Having supplements such as vitamin C, zinc, and vitamin D.
- Adding turmeric, ginger, and garlic to the diet.


What Distinguishes Vitamin D From Vitamin D3?

The fundamental distinction between vitamin D and D3 is that vitamin D is a fat-soluble vitamin that controls the body's calcium and phosphorus levels. In contrast, vitamin D3 is the natural version of vitamin D generated by the body from sunshine.


Which Fruits Are Healthy for COVID?

- Gooseberries and grapes (amla, even dried or pickled).
- Oranges.
- Red bell pepper (antioxidants + vitamin C). 
- Tangerines. 
- Lemons. 
- Brussels sprouts, cauliflower, and broccoli. 
- Capsicums. 
- Strawberries, cantaloupe, papaya, and similar fruits.


Which Symptoms Indicate a Vitamin D Deficiency?

The symptoms of vitamin D deficiency include the following:
- Frequent diseases or infections. 
- Fractures of bone and joint pain. 
- Depression. 
- Wounds heal slowly. 
- Immune disorder.
In children:
- Irritability or lethargy. 
- Fractures or bone discomfort. 
- Dental abnormalities and developmental delays.


What Effects Does COVID-19 Have on Lungs?

COVID-19 has the potential to result in lung problems such as pneumonia and, in the most severe cases, acute respiratory distress syndrome (ARDS). Another potential COVID-19 consequence, sepsis, can permanently injure the lungs and other organs.


What Effect Do High Vitamin D Dosages Have?

A buildup of calcium in the blood (hypercalcemia) can result in nausea, vomiting, weakness, and frequent urination. This is the main reason for vitamin D poisoning. In addition, calcium stones may occur in the kidneys, and bone discomfort may result from vitamin D intoxication.


How Does Vitamin D Control Immunological Function?

Immune system cells are subject to a variety of vitamin D-related actions. It prevents B cell differentiation, immunoglobulin secretion, and B cell proliferation. The health of the bones, muscles, and nerves depends on vitamin D. The immune system is assisted by vitamin D in its defense against viruses and bacteria.


How Can One Tell Whether They Have COVID in Their Lungs?

The following are typical signs of COVID-19 respiratory infections in the airways and lungs.
- Shortness of breath.
- Chest tightness.
- Wheezing when one exhales. 
- Strong cough that produces mucus.


How Quickly Does Vitamin D Start to Work?

If one consistently takes supplements and has a vitamin D deficiency, they can see improvements in four to six weeks. Nevertheless, that period may change based on vitamin D levels at the outset. For example, after a few weeks, it is anticipated that taking 1,000 IU of vitamin D3 per day will increase blood levels by ten nanograms per milliliter.


What Time of Day Is Ideal for Taking Vitamin D?

As part of their morning ritual, many people prefer to take their dietary supplement pills first thing in the morning. In this manner, it is simple to remember and can be taken before breakfast or as soon as one gets out of bed. Because of this, taking a vitamin D pill is an excellent idea, but one should also have a nutritious breakfast before doing so.


Which Illnesses Does Vitamin D Guard Against?

Cardiovascular diseases, diabetes, malignancies, autoimmune disorders, infectious diseases, and other conditions are all strongly linked to vitamin D. With the biological actions of vitamin D, it is now widely regarded as a hormone rather than one of the traditional dietary vitamins, according to many specialists.
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Dr. Mohammed Abdul Nasir
Dr. Mohammed Abdul Nasir

Pain Medicine


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