COVID-19 – Vitamin D and Immunity

Dhanalakshmi MSc,Mphil, Founder, Care Through Nutrition

Nowadays we see lot of articles and studies related to vitamin D and Immunity. But any article without evidence is not worth. Here in this article I will be giving few research evidences on how vitamin D is related to immunity. In these evidences we could see people with low vitamin D have low immunity. They are susceptible to various bacterial and viral infections. We get abandon vitamin D from sun rather than from food. Also one more fact is that, more darker the skin, the more slower you produce vitamin D.


To say it in a simple way how Vitamin D is produced in our body, look at the following flowchart ,

This explains that the UV rays from the sunlight is absorbed by the skin and the dermis layer produces inactive form of vitamin D (cholecalciferol) which then goes to the liver and kidneys to produce active Vitamin D (1,25-dihydroxyvitamin D3). This active form then circulates into blood to perform its various functions like calcium absorbtion etc.

One other important function of Vitamin D is to improve immunity. For this we need to know what happens when the lungs get infected by a pathogen.

When the lung cells deduct an antigen, the immune cells respond to that by producing pro-inflammatory cytokins, which produces more fluids inside the alveoli. This fluid accumulation inside the lungs caused difficulty in gases exchange and hence make breathing difficult. This condition is called ARDS (Acute Respiratory Distress Syndrome). This happens with all lung infections including pneumonia, influenza, covid etc.,


More than a century ago (1849), a British physician C.J.B. Williams disribed the use of cod liver oil in treatment of tuberculosis, as cod liver oil contains rice amount of vitamin D. He showed that among his tuberculosis patients, 206 out of 234 showed a marked improvement after treatment with cod liver oil.

Another study “Evidence that vitamin D supplementation could reduce risk of Influenza and COVID-19 infections and deaths” says that vitamin D can induce cathelicidin and defensins that can lower viral replication thereby reducing pro-inflammatory cytokins production, there by reduce inflammation. It also says that the COVID-19 outbreak occurred during winter, a time of low sunlight, hence people having low vitamin D levels. Also they say mortality rate in COVID increases with age and with chronic disease comorbidity, both of which is associated with vitamin D deficiency.


If we see in India above 70% of the population are vitamin D deficit. Vitamin D is widely got from sunlight. In food, it is present in animal source like fish, cod liver oil and very little amount in milk. In India, very rarely the milk is fortified with vitamin D. For vegetarians, its difficult to get vitamin D from food source. It would be great if the Government takes steps to fortify some of our staple foods like wheat, milk, curd, ghee ect with vitamin D.


Different studies show different recommended doses. The RDA valve for vitamin D is 600 IU for younger adults and 800 IU for older adults above 70 years.

Normal serum vitamin D levels less than 20 ng/ml is considered deficit. 50-70 ng/ml is considered optimal.

So check your vitamin D levels and consult a physician for the correct dose if you are vitamin D deficit.

NOTE: Self medication is dangerous. Consult a physician before taking vitamin D supplementation.

Published by Care Through Nutrition

Hai I am a diet consultant interested in giving people the awareness about healthy eating habits and also keen to tell the public not to forget the traditional food habits which are healthy when compared to now.

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