• Dr. Ashley Stapleton ND

What Does Vitamin D Have to do With COVID-19?

Vitamin D, the sunshine vitamin, is the only nutrient we absorb through our skin. As mammals, we count on the sun to get the bulk of our vitamin D. It's absorbed from by short wavelength rays changing the 7-dehydrocholesterol in the skin to bioavailable vitamin D. There are some food sources, but actually, very few foods contain vitamin D. The ones that do, include: cod liver oil and other fish oils, egg yolk, fortified whole milk, and spinach. That is why supplementation, especially in the winter, is so important. During the winter in Canada, we have short, cold days, very long, dark nights and we are not able to acquire vitamin D through sunlight exposure. These rays are not strong enough for that conversion process to take place, that is why most Canadians have low serum vitamin D in the winter.

Why do we need vitamin D? It has many jobs to perform in the body. One of its main functions is to enhance calcium absorption (that is why it is fortified in milk), and it is critically important to bone health. However, the most relevant right now, is its role in immunity. Vitamin D deficiency is one of the factors that make us so susceptible to infection, specifically in the winter months.

There are some studies and clinical trials that show vitamin D supplementation reduces the risk of influenza. There is also evidence that vitamin D may reduce the risk of COVID-19.

  • The outbreak is occured in the winter, this is typically a time when serum vitamin D concentrations are the lowest.

  • There are fewer cases in the Southern Hemisphere, when it was near the end of Summer.

  • There is evidence vitamin D deficiency contributes to acute respiratory distress syndrome.

  • Advanced age and chronic disease comorbidity have a higher likelihood of fatal prognosis and both are associated with lower vitamin D concentration. This is due to less time spent in the sun and lower concentrations of 7-dehydrocholesterol in the skin as a person ages.

Vitamin D has several mechanisms that contribute to improved immunity: (1) physical barrier, (2) innate immunity and (3) adaptive immunity.

1. Vitamin D supports the integrity the junctions that prevent the transmission of fluid or other molecules, allow for effective communication between cells and structurally support those cells. A functioning physical barrier is our first line of defence against any disease.

2. Cathelicidins and defensins are small protein building blocks that are a part of our innate immune function. They directly attack microbes leading to infection. In some cases of severe COVID-19 the innate immune system can create what has been labelled, a "cytokine storm". This is a last ditch effort of the immune system to throw everything it's got at the virus, resulting in out-of-control inflammation in the lining of the lungs. Vitamin D "helps" the immune system to reduce concentrations of those pro-inflammatory cytokines, that may lead to pneumonia, as well as increasing concentrations of the anti-inflammatory cytokines.

3. Vitamin D also works through our adaptive immune system, which is responsible for "memory" of a bacteria or virus. This is the mechanism that allows us to acquire lifelong immunity to some diseases. Through this pathway, Vitamin D suppresses the wrong type of inflammation and supports anti-inflammatory cytokines.

To ensure your immune system is functioning at the highest level, it is important to make sure you are not deficient in vitamin D. If you live in Canada in the winter, spend most of your time indoors, and always wear sunscreen/cover up outside then there is a very good chance you are deficient in vitamin D. This is especially true if you have darker skin, as the higher melanin in the skin shields the UV light that is necessary to convert vitamin D. If you are not currently supplementing, consider taking 10,000 IU/day of vitamin D3 for 2-3 weeks to rapidly increase vitamin D concentrations, in order to reduce the risk of infection and complication from COVID-19. Follow this initial high dose with 5000 IU/day until summer time. Randomized controlled trials and large population studies are still needed to evaluate these recommendations.

Please be sure to check with your healthcare provider if supplementing in large doses, as overdosing can cause arteriosclerosis and premature symptoms of senility. Vitamin D is just one part in a balanced diet and one factor in supporting your immune system. Book a tele-consultation today to get into a more detailed plan on how to support your health.

Grant, W.B.; Lahore, H.; McDonnell, S.L.; Baggerly, C.A.; French, C.B.; Aliano, J.L.; Bhattoa, H.P. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths.Nutrients2020,12, 988.

Mawson, and Anthony R. “Role of Fat-Soluble Vitamins A and D in the Pathogenesis of Influenza: A New Perspective.”ISRN Infectious Diseases, Hindawi, 19 July 2012,

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