Featured Post: Vitamin D for Immune Support

Vitamin D for Immune Support

By Dr. Julie Mardian, ND

Written September 22, 2020

Over the last few months, there have been numerous studies showing a strong correlation between vitamin D levels and COVID-19 outcomes.

Vitamin D deficiency is an issue for Canadians especially as the days get shorter and we spend more time indoors. Statistics Canada reports that up to 40% of Canadians have inadequate levels of vitamin D during the winter months. With this brief article, I want to provide a current update  about the latest information linking low levels of vitamin D and health outcomes for COVID-19 patients, along with highlighting  the importance now for people to actively increase vitamin D levels with diet and supplementation for themselves and their children and family members. By improving our vitamin D levels, we can help our immune system and increase our defenses against viruses during the fall and winter months.

Since the spring of this year, there have been over 20 studies showing strong correlational evidence that having deficient or inadequate levels of vitamin D in the blood, puts you at higher risk for COVID-19 infections, complications and even death. Doctors and researchers in the U.S, Korea, Israel and Indonesia have all shown similar findings when measuring vitamin D levels in patients with COVID-19 infection - the lower a patient's vitamin D levels, the more symptoms and complications there are with COVID-19 infection. 

As recently as September 17, 2020,  Dr. Michael Holick, professor of medicine from Boston University reported that after studying the blood samples of more than 190,000 Americans, he found that those who had deficient levels of vitamin D had a 54% higher COVID-19 infection rate compared to those with adequate levels of vitamin D in the blood. Studies that show strong associations do not necessarily mean causality, but with repeated findings between this relationship, it is wise to take action. 

Vitamin D plays an important role in modulating and strengthening the immune system, it can lower viral multiplication (how fast it reproduces), it can make you less susceptible to an upper respiratory infection and it reduces concentration of pro-inflammatory cytokines (proteins). Cytokines produce inflammation that causes injury to the lining of the lungs (leading to pneumonia). One of the complications of having COVID-19 infection is something called the “cytokine storm” where large amounts of cytokines are released into the bloodstream affecting inflammation and causing tissue damage throughout the body. Having adequate levels of vitamin D have been shown to help reduce this. 

Since it is difficult for Canadians to make enough vitamin D naturally from the sun during November to May it would be helpful to have your levels measured. Levels in the blood should be above 50 nmol/L. The reference range for optimal is between 75-250 nmol/L. This is easily measured by a simple blood test. Please talk to your doctor about measuring your vitamin D levels this fall because it is so important to have a strong immune system that can better defend against viruses.

Vitamin D can be found in food sources such as egg yolk, fatty fish, portabella mushrooms and whole milk. Unfortunately,  the amounts in these foods are not enough to get our levels up to optimal numbers. Talk to your healthcare provider about supplementation, but generally during the fall and winter, children ages 6 months to 12 months should be given 800 International Units (I.U) of vitamin D per day, children ages 1 to 6 can supplement with 1000 I.U per day and children ages 7 to 13  up to 2000 I.U per day. I recommend for all adults to take a minimum of 2000 I.U- 3000 I.U during the fall and to double it during the winter (heavier adults need to supplement with more). These amounts can be adjusted accordingly to each individual situation. 

These levels are higher than the Recommended Daily Allowance (RDA) by Health Canada, but that is because the RDA is to only prevent deficiency in vitamin D, it is not for “optimal” levels - which is what we should be striving for. Again, please talk to your health care provider about your specific case, people with kidney disease need to be careful when supplementing with vitamin D. Vitamin D is easily found at health food stores, pharmacies and grocery stores in the pharmacy section and is relatively inexpensive.  Make sure you supplement with Vitamin D3 (the active form). Gel capsules, chewable or liquid is best. 

We do need to be proactive in supporting our health and defenses  this fall and during the winter months.  Vitamin D supplementation is one tool that almost everyone  has easy access to, it's inexpensive, safe to use and shown to be helpful in strengthening our immune systems. 

For more information, please visit:

covid.us.org/vitamin-d and vitamindsociety.org


  1. A little footnote on Vitamin D...
    I sometimes hear from clients that they are supplementing with Vitamin D that their blood levels are not going up. D3 is the most absorbable vitamin D but also fully synthetic, which means almost all vitamin D currently on the market is synthetic. The shop.mnm.ca online store has a number of non-synthetic brands and one of my favorites is Prosorb-D by Protocol which is made from Lanolin (sheep wool). The sheep absorbs the Vitamin D from the sun and has done all the work converting it to a useable state. Taking this Vitamin D has much more benefit than the synthetic type most commonly found in your local drug store. Click here for a link to the product.


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