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Does Vitamin D Supplementation Improve Immunity to Covid-19?

Edited by: Luxshimi Nageswaran


The information provided in this article is not medical advice. Please speak to a healthcare professional if you are concerned about your vitamin D levels and/or before consuming any dietary supplements or natural health products.

What is Vitamin D?

You may have heard that consuming milk is a good source of vitamin D, but what really is vitamin D? Vitamin D is a prohormone that can be synthesized by the body in the presence of sunlight or UV radiation (1). This occurs due to a vitamin D precursor within the skin that gets converted to previtamin D in the presence of sunlight, which is further converted to vitamin D3 (2). Vitamin D is activated from its D3 form via hydroxylation reactions in the liver and kidneys, which allows it to support bone growth and enhance or suppress the activity of genes that regulate cell growth of cells, such as immune and nervous cells (2).

Sources of Vitamin D

Examples of sources of vitamin D include oily fish like salmon, egg yolks and fortified dairy products (2). It is to be noted that the body can make vitamin D with little sun exposure, which is where outdoor physical activity may play a role in the amount of vitamin D made by the body. Those who are not outdoors often, which is a circumstance many have found themselves in due to the COVID-19 pandemic, or live in areas with little sunshine may need 2 cups of fortified milk/day for sufficient vitamin D intake (2).

Safe sunlight exposure to boost vitamin D levels is recommended in countries within northern latitudes, such as Canada. Exposing skin to sun 2-3 times per week for 5-10 minutes is enough to maintain vitamin D synthesis for white skinned individuals, whereas darker skinned individuals (i.e., skin type 5) may require about 25 minutes of sun exposure (2,3).

The Big Study Explained

The Journal of Medical Virology recently published an article called “Vitamin D deficiency is associated with COVID-19 positivity and severity of the disease”, looking at the relationship between vitamin D levels and patient responses to COVID- 19 (4).


The study was conducted in Tokat, Turkey, and consisted of 2600 COVID-19 positive (tested via PCR tests) patients over the age of 18. The patients (n=227) that were considered in this study had their vitamin D levels measured within a 6-month period prior to testing positive for COVID-19, as identified via their medical histories. Based on their vitamin D levels, patients were divided into four groups: Group 1 (patients with vitamin D levels less than 10 ng/ml), Group 2 (patients with vitamin D levels between 10 and 20 ng/ml), Group 3 (patients with vitamin D levels between 20 and 30 ng/ml) and Group 4 (patients with a vitamin D levels higher than 30 ng/ml).


Over 94% of the 227 COVID-19 positive patients had vitamin D levels below 30ng/ml and only about 6% of patients had vitamin D between 30 and 40 ng/ml. In comparison, 260 patients who were admitted to Tokat State Hospital for other reasons beyond COVID-19 and had their vitamin D levels examined were identified. Results found that about 93% of non-COVID-19 patients had vitamin D levels below 30ng/ ml.

Also, hospital stays for COVID-19 positive patients in Group 4 were shorter in comparison to patients from Groups 1, 2 and 3. Moreover, lung segments were the least affected in COVID-19 positive patients in Group 4 who had vitamin D levels greater than 30ng/ ml.


The study indicates that adequate vitamin D intake resulted in lower incidences of COVID-19 positivity, rendering a strong relationship between vitamin D deficiency and greater COVID-19 positivity rates. Findings from this study suggest that severe vitamin D deficiency was about 30% higher among COVID-19-positive patients in comparison to the public. Therefore, adequate vitamin D levels alongside lifestyle modifications such as physical activity are important factors to improving the body’s immune response to pathogens, and potentially COVID-19. Although more research is required to determine if vitamin D can defend against COVID-19, it is important to maintain a healthy lifestyle that involves physical activity and healthy eating, as this overall has a positive impact on the immune system (6).

Our Conclusions

The strong relationship between higher vitamin D levels (>30ng/ ml) and decreased COVID-19 rates requires further study through randomized studies to definitively determine if vitamin D levels affect the risk of COVID-19.

Overall, to prevent vitamin D deficiency, supplementation with vitamin D according to government guidelines is recommended, alongside consuming a balanced diet (6). With respect to the circumstances of COVID-19, it is even more pivotal to engage in short and safe sunlight exposure daily from March to September during the afternoon when appropriate. Forms of sun exposure can be taking a walk/run outside during your lunch time, doing an outdoor workout (while maintaining social distancing guidelines), or going on a bike ride —which is something we advocate for at Enayble Health.


  • Adequate Vitamin D intake alongside good nutrition and physical activity are crucial to maintaining a strong immune system

  • Those at risk of poor vitamin D status, such as those living in the northern hemisphere (i.e., Canada, northern parts of the United States), may need vitamin D supplementation according to government guidelines during the winter months or when confined indoors for long periods of time (i.e., isolation due to COVID-19)

  • There is a strong relationship between an increased vitamin D intake of >30ng/ ml and a decreased risk of COVID-19, but more research needs to be acquired

  • Getting outdoors for a walk or any other form of physical activity daily for 10-25 minutes when sun exposure is the strongest, such as during lunch time, can aid in maintaining the body’s vitamin D levels


  1. Anthony W Norman. From vitamin D to hormone D: fundamentals of the vitamin D endocrine system essential for good health. The American Journal of Clinical Nutrition. 2008;88(2): 491-499.

  2. Whitney E, Rolfes SR, Hammond G, Piché LA. Understanding Nutrition, Second Canadian Edition. Toronto (ON): Nelson Education Ltd; 2016. 736p

  3. Webb AR, Kazantzidis A, Kift RC, Farrar MD, Wilkinson J, Rhodes LE. Colour counts: sunlight and skin type as drivers of vitamin D deficiency at UK latitudes. Nutrients. 2018;10:457–3.

  4. Demir, M, Demir, F, Aygun, H. Vitamin D deficiency is associated with COVID-19 positivity and severity of the disease. J Med Virol. 202; 93(5):2992– 99.

  5. Lanham-New SA, Webb AR, Cashman KD, Buttriss JL, Fallowfield JL, Masud T, Hewison M et al. Vitamin D and SARS-CoV-2 virus/COVID-19 disease. BMJ Nutrition, Prevention & Health 2020;0.


  7. Walking Photo:

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