The Connection Between Vitamin D and Immunity - Blog - Persona Nutrition

The Connection Between Vitamin D and Immunity

With the world in a global health pandemic, cold and flu season approaching, and the changing seasons, immunity is at the forefront of most of our minds. Vitamin D has been gaining popularity for its proposed benefits in terms of immune health. But does the science support the claims regarding vitamin D and immunity?


Vitamin D

To understand the role of Vitamin D within the immune system we must first understand exactly what Vitamin D is. Vitamin D is one of four fat-soluble vitamins, meaning it is absorbed and transported through the body in fat globules. Fat-soluble vitamins are stored in the body within cells and tissues. Since fat-soluble vitamins are stored in the body, there is an upper limit (UL) for them. The UL is the maximum daily amount an individual can consume without causing adverse health effects. The UL for Vitamin D is 4000 IU for adults.

Vitamin D has two forms, Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D2 is typically man-made and added to foods or supplements. While Vitamin D3 is the natural form, often referred to as the “sunshine vitamin”; we can naturally synthesize Vitamin D3 from the sunlight when it hits our skin. About 10-15 minutes of sun exposure multiple times per week is sufficient for adequate Vitamin D3 absorption. However, several factors can hinder the absorption of Vitamin D3 such as skin color, time of day, UV strength, season, geographic location, and use of sunscreen. Despite the ability to naturally obtain Vitamin D from the sunlight. Vitamin D deficiency remains quite prevalent among the world’s population, especially in the winter months and northern hemisphere.1


The role of the Immune System

Vitamin D is most widely known for its role in the formation and maintenance of normal bones and the metabolism of calcium and phosphorous. However, over 50 genes are be known to regulated by Vitamin D, most of which are unrelated to mineral metabolism.2 Emerging research shows the role and importance of Vitamin D within the immune system.

The proposed role of Vitamin D within the immune system is its ability to stimulate a greater production of T cells.3 Increased production of T cells may help to increase the production of anti-inflammatory cells and decrease the production of inflammatory cells.4 This may help the body fight against infections and foreign invaders. 3


The COVID Connection

Several studies have found a correlation between Vitamin D deficiency and testing positive for COVID–19. Given the role of Vitamin D in the immune system, it is plausible to associate a Vitamin D deficiency with a decreased immune system possibly increasing the susceptibility to illness. However, further research is needed to determine the role of Vitamin D in the prevention and treat of COVID-19.


Take home message

There is much to learn about the role of Vitamin D within the immune system. Adequate amounts of Vitamin D may help to promote a healthy immune system. The recommended amount of Vitamin D an adult should consume daily is 600 IU. Supplementing with the active form of Vitamin D3 (cholecalciferol) may help to provide you with an adequate amount of Vitamin D to help prevent nutritional deficiencies from occurring if you are at risk. Remember, Vitamin D is a fat-soluble vitamin, there is a risk for toxicity with intakes greater than 4000 IU per day.



  1. Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. [Updated 2020 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from:
  2. Omdahl JL, Morris HA, May BK. Hydroxylase enzymes of the vitamin D pathway: expression, function, and regulation. Annu Rev Nutr. 2002;22:139-66. doi: 10.1146/annurev.nutr.22.120501.150216. Epub 2002 Jan 4. PMID: 12055341.
  3. Louise Saul, Iris Mair, Alasdair Ivens, Pamela Brown, Kay Samuel, John D. M. Campbell, Daniel Y. Soong, Nadine Kamenjarin, Richard J. Mellanby. 1,25-Dihydroxyvitamin D3 Restrains CD4 T Cell Priming Ability of CD11c Dendritic Cells by Upregulating Expression of CD31. Frontiers in Immunology, 2019; 10 DOI: 3389/fimmu.2019.00600
  4. Aranow C. Vitamin D and the Immune System. Journal of Investigative Medicine 2011: 59:881-886.

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