Role of Vitamin D and COVID-19 – what we know

In March 2021, the world marked one year of the pandemic.  Like an ocean wave, the COVID-19 virus has been relentlessly attacking nation after nation without respite.  Soon, scientists rolled up their sleeves and fast-tracked their research to study the virus genome.  Today we now know more about the virus and ways to tackle it. The number of treatment options increased, and the death rates have reduced considerably.  This paper examines briefly the role of Vitamin D and COVID-19 and the latest we know about it.  

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Significantly the number of available drugs for the management of the COVID-19 symptoms have increased over the months.  Along with the vaccines’ availability, there are several vitamins and minerals, assisting in reducing the viral attack’s intensity. However, the role of vitamin D and COVID 19 is a subject with its fair share of promoters and naysayers.   A  search of Vitamin D and COVID-19 will throw up several pages vouching for the importance of Vitamin D in managing the infection rate of COVID-19.

COVID-19 second wave

When the second wave of the pandemic raged across Europe and America, panicked governments quickly announced lockdowns of varying intensity. It was a tough decision for the governments to take.  Especially, considering the colossal economic loss that the countries suffered during the first phase of lockdown.  It was a case of damned if you do and damned if you don’t.

Though the cases are increasing, the number of deaths is considerably less than the first wave of the virus. According to a study conducted by the British Medical Journal and published on 21 October 2020 (, covid-19 deaths (in England) were now more than doubling fortnightly (a rate of 2.2). However, the “rate of increase . . . is currently lower and slower than in March 2020, when it was initially 10-fold”.

The study was conducted when the second wave started. But the recent case and fatality figures from the European Centre for Disease Prevention and Control (ECDC) show that while recorded Covid-19 cases are spiking in the United Kingdom, France, Spain, Germany and other European countries, deaths are not rising at the same rate (

Vitamin D deficiency and COVID 19

As per the records, the virus attack is most intense during the winter when the sunshine is at its minimum.  This is when the vitamin D levels are the lowest among the people living in the northern hemisphere. Vitamin D deficiency seems to be having a direct correlation to the high infection of COVID-19 patients.

In a study published in Nutrients 2020, researchers studied the role of Vitamin D supplementation and how it could potentially reduce the risk of influenza and COVID-19 infections and death. The recommendation was to take 10,000 IU/d of Vitamin D3 for a few weeks to rapidly raise the concentration and then taper it down to 5000 IU/d.  This would help in reducing the risk of infection of people at risk. The goal is to raise the concentration of Vitamin D above 40-60 ng/mL.

Backed by a growing body of research, vitamin D supplementation is now an acceptable therapeutic agent for COVID-19 patients.  The sale of Vitamin D supplementation has grown, and according to Nielsen data of December 2020, the sales increased by 41.5% year over year.   Not everyone agrees with these research findings.  According to some experts, the available evidence is insufficient to conclusively prove that Vitamin D prevents or reduces the COVID 19 disease.

What is a Vitamin?

Our body requires certain chemical compounds, albeit in tiny doses, for proper functioning. Moreover, these chemical compounds are not only necessary, but a deficiency of them will cause illness. Known as vitamins, we find most of them in the foods we eat.

The term vitamin means “vital amine”.   American biochemist Casimir Funk coined the term ‘vitamin’ in 1912 in the book “The Vitamines”.   He was researching the cause of the disease beriberi when he discovered that people on a diet of brown rice were less vulnerable to the illness beriberi.  Subsequently, he isolated the substance in brown rice, and since it contained an amine, he called it “Vitamine”.  The substance he identified was niacin or Vitamin B6. 

The discovery of other vitamins followed this. The deficiency of the vitamins caused specific illnesses, and the treatment of these illnesses was by taking supplements or the foods that contain the vitamins.  In developing countries, lack of vitamins has become a major public health problem, and governments often focus on providing food fortified with vitamins through the public distribution system.

Types of Vitamins

There are two types of vitamins – water-soluble and fat-soluble.  Water-soluble vitamins.

Our bodies quickly absorb water-soluble vitamins.  Since they are water-soluble, the body is not able to store them for future use.  Because of this, our bodies replenish the vitamins, either through food or by supplements.  The vitamin B group and vitamin C are examples of water-soluble vitamins.

Our adipose tissues store these fat-soluble vitamins. Since they are stored, there is no need to replenish them often. Vitamins A, D, E and K are examples of fat-soluble vitamins.

Is Vitamin D a hormone?

Vitamin D refers to many compounds. The kidneys make  1,25 hydroxyvitamin D or calcitriol. This is technically a hormone circulating in our blood.  The majority of vitamin D in our blood is not a hormone. Vitamin D is a prohormone.  Exposing the skin to the sun helps create vitamin D. The molecular structure of vitamin D is like the steroid hormones cortisol, estradiol, etc. 

Vitamin D behaves more like a vitamin, which is an essential nutrient. We require vitamins only in small quantities. In comparison, we require proteins, carbs or fats in large quantities for normal body function.  Vitamins play an important role in enzyme function and regulation. Being fat-soluble, it can pass through membranes and reach the cellular portion of the cell’s nucleus. It can influence cell behaviour.

Therefore vitamin D behaves more like a vitamin than a hormone.  Sunshine is a major source of vitamin D.  Spending at least 20 minutes a day in the sun give around 10,000 IU of vitamin D.  Spending time in the sun also helps in the production of melatonin which is an essential chemical for sleep.

Types  of Vitamin D

Vitamin D is a group of chemical compounds. The two major forms are vitamin D2 or ergocalciferol and vitamin D3 or cholecalciferol. The other forms are D1 or a mixture of molecular compounds of ergocalciferol with lumeisterol.  D4 or 22 dihydroergocalciferol and vitamin D5 or sitocalciferol. Vitamin D2 and D3 are the two major forms that are extensively studied and well absorbed in the small intestines.

Whether from exposure to the sun or as a food supplement, Vitamin D is biologically inert and cannot be used by the body unless it is converted to a different chemical.  Hence, the liver converts the active form of vitamin D to calcifediol. The kidney now takes over and coverts calcifediol to calcitriol, the biologically active form of vitamin D.  It is the calcitriol that circulates in the blood regulating the concentration of calcium and phosphate and assisting the skeletal system.

Uses of Vitamin D

Whether vitamin D is a hormone or a vitamin, there is no controversy on the importance of the vitamin to the well being of ourselves.  It plays an important role in maintaining skeletal calcium balance by promoting calcium absorption in the intestines. A deficiency can lead to lower bone mineral density and cause osteoporosis.  Elderly, especially women, are prone to osteoporosis, causing hip fractures.  Taking vitamin D with calcium regularly prevents osteoporosis.

This vitamin’s receptors are located within our cardiovascular system, lungs, pancreas, skeletal muscle, skin and reproductive organs.  It also influences the immune system.  The white blood cells, our main line of defence, expresses vitamin d receptors. It is said that low vitamin D may be associated with adverse outcomes in certain cancers

In another study in Germany, researchers found that the use of Vitamin D supplements reduced cancer deaths and a substantial reduction in the health care expenses in adults over 50.

Our muscular and nervous system need Vitamin D.  It is an important element in the neural transmission between the brain and the body.   Besides, it also reduces inflammation and improves cell growth, neuromuscular and immune response and improves healing in cardiovascular disease. 

Role of Vitamin D and COVID-19

The role of vitamin D and COVID-19 has its fair share of promoters and naysayers.

There is mounting research that clearly establishes the correlation between the role of deficiency in vitamin D and the potential increase in the risk of severe respiratory infections.  The British Medical Journal published a report in February 2017. A report published in the British Medical Journal in February 2017 carried the results of a study of 25 eligible randomized trials of 11,321 participants aged 0 to 95 years.  As per the study, vitamin D supplementation reduced the risk of respiratory tract infection among all the participants.

Significantly the fact that vitamin D reduces the severity of acute respiratory distress syndromes became important with the declaration of the pandemic and COVID-19 treatments. Several studies showed a significant association between vitamin D deficiency and an increase in the severity of the disease in COVID-19 patients.

At the same time, the US National Insitute of Health found insufficient evidence about the role of vitamin D in either prevention or treatment of COVID-19. The UK National Insitute for Health and Care and Excellence made similar recommendations.  Both advocate the use of vitamin D for traditional and established reasons like bone and muscle health. 

Possible correlation of Vitamin D and COVID-19

It is a known fact that the COVID-19 did not affect most of the developing nations.  There were many speculations that the death toll in countries in Africa would be huge, considering the poor health infrastructure and the lack of health equity amongst the people. 

Most of the countries in Africa, except for South Africa, were relatively less affected that the European countries and America. Moreover, it is a well-known fact that sunlight is abundant in Africa.  Given that most of the population in Africa are involved in outdoor work, they are exposed to sunlight for long hours.  Therefore this automatically increases the chances of their skins, absorbing the rays and manufacturing vitamin D. Surely, this could be an important reason for the low infection rate in Africa?   Consequently, this might explain that the virus did not cause the “anticipated” death toll in Africa.

In Europe and the Americas, the winters are harsh, and sunlight’s availability is far lesser.  Ecologically, the settlers’ skin in these regions lost its darkness, mainly enabling them to absorb Vitamin D from the sunlight. The lighter the skin, the better absorption of this important vitamin.

In Africa, dark skin was useful because the body adjusted itself to the long hours of sunlight. Without the dark skin, the bodies would have suffered ultraviolet radiation due to constant sunlight exposure. The dark skin helped to adjust the absorption of vitamin D in an optimum way.   

Higher death toll in America

How would then someone explain the increased number of deaths of African Americans in the US?  Again if we examine the ecology, we have the answer.  As discussed in the earlier paragraph, sunlight availability in these countries is limited, especially during the winter.  The sun shines only for a small period of the year, and the bodies adapted to absorb the sun rays.  When the sun shines, the people with fairer skin can ‘grab the opportunity and absorb as much sunlight as possible.  African Americans could not use this opportunity because their skin absorbs vitamin D at a much slower rate.

Nature is yet to come to terms with the advent of the different races into unfamiliar geographies.


Moreover,  it is advisable to increase the availability of this vitamin in the body naturally.    About  20-30-minute exposure to the sun is said to be sufficient to give an adequate dose of this vitamin for the day. Please remember that this exposure has to be directly in the sun, preferably between 10 am and 4 pm.  Whereas, sunlight reflected through glass does not provide this benefit.  Alternatively, people who are not able to get this from the sunlight for whatever reason should ensure that they consume lots of fatty fish like tuna, mackerel, salmon, or mushroom, beef liver, etc.

The last option is taking supplements.  Please consult your doctor if you are eligible to take the supplement and the dosage that you should be taking.

Here is an excellent resource on the details of Vitamin D for your further reading

Please remember that Vitamin D does not prevent COVID-19 infection. It is not a substitute for the hygiene protocols laid down the health experts and Governments. The studies show that Vitamin D has proven that it can reduce the effect of the COVID-19 attack.


As a person interested in health and preventing/curing illnesses, I have done extensive readings on the subject matter of health and nutrition.  I am not a medical doctor or a qualified nutritionist to give advise or suggest medications.  The information given is only for your general awareness, and please consult your doctors for any treatment or advise.  Please do not tell me that you were blind enough to follow me and indulge in the wrong medication!


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