COVID-19 and Vitamin D

This is a translation of the article originally published in forskersonen.no in Norwegian on 7 November 2020.

A review of research published before the pandemic has shown that the level of vitamin D affects how susceptible we are to infectious diseases of the upper respiratory tract.

Vitamin D can affect our immune system by stimulating it during infections from viruses and bacteria. In order to be well equipped against infectious diseases, including COVID-19, I think we should make sure we get enough of this vitamin. Several research groups are now studying the connections between vitamin D levels and how susceptible we are to being infected with COVID-19, and how severe the symptoms we get from the virus are.

We still do not have a complete overview of how the vitamin affects us, but several findings so far indicate that there is a connection. Rose Anne Kenny is leading a major study in Ireland where they are studying mortality from COVID-19 infection in regard to vitamin D levels. In an interview with The Lancet Diabetes & Endocrinology, she is suggesting that all public health services should recommend the population to take vitamin D supplements during the pandemic.

Adrian Martineau, the doctor and researcher behind a large study on how diet affects covid-19 infection, also believes that ensuring that people do not have a vitamin D deficiency is safe, inexpensive and can have a preventive effect.

We do not get enough through our diet.

Vitamin D is a fat-soluble vitamin that occurs naturally in some types of food and is added to some products. However, our diet is generally not sufficient to maintain good vitamin D levels. Cod liver oil is an important source for us who live in Norway. In addition, the vitamin is also produced in our body when the skin is exposed to the sun. However, during the winter season in Norway, the sun is too weak to ensure vitamin D production in our skin.

Global surveys conducted in 44 countries show that almost 40 percent of the population has lower amount of vitamin D than the recommended. As many as 7 percent had levels that are categorized as critically low. The levels vary with regard to age groups, ethnicity, from country to country, continent to continent, in addition to the season, but give a clear indication that vitamin D deficiency is a global challenge for public health.

Vulnerable groups should avoid vitamin D deficiency

Vitamin D deficiency is more prevalent in people with dark skin, compared to people with light skin. Melanin in the skin protects against UV light by absorbing the rays, but as a consequence vitamin D production is reduced. It is a known issue that people with high melanin levels who live in the northern hemisphere often have too low levels of vitamin D.

Although there of course are other important factors that come into play, this may be a contributing explanation for why the course of the disease from COVID-19 infection has proven to be more serious for this group of people. Also the elderly often have a deficiency in vitamin D. Although there are several reasons why the elderly are more vulnerable to COVID-19 infection, I think there is reason to believe that this group can also be better equipped against disease by avoiding low levels of vitamin D.

In Norway, the recommendation is that everyone under the age of 75 should take 10 micrograms of vitamin D every day. The oldest part of the population, aged 75 and older, should absorb twice as much. If you follow these guidelines, I think it can help us to be better prepared for respiratory diseases.