Vitamin D and Your Immune System

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Why Vitamin D Is Important

Vitamin D: The Key to Your Immune System

Vitamin D is an important vitamin with many benefits. It helps the body absorb dietary calcium, helps build strong bones and teeth, and helps maintain and support healthy immunity. Vitamin D deficiency has been linked to many different conditions, including heart disease, [1] high blood sugar levels,[2] occasional low mood [3] and aches and pains. [4] Vitamin D deficiency is more common in the winter, with less sun exposure, with darker skin, with advancing age, and when living at northern latitudes. [5]

Vitamin D deficiency is very common in Canadians, and it is estimated that 90% of Canadians have inadequate intake of vitamin D from dietary sources alone. [6] Even when supplements are considered along with diet, more than half of Canadians are still vitamin D deficient. [6] The great news is that vitamin D deficiency can be addressed and prevented! While the body makes vitamin D when skin is exposed to the sun, dietary and supplemental sources are also excellent choices.

Vitamin D and Immunity

Vitamin D is incredibly important for healthy immune function.  The immune system has two parts: the faster, innate immunity which we are born with, and the slower, but more specific adaptive immunity which develops over time. Both the innate immunity cells and the adaptive immunity cells have vitamin D receptors, and when there is not enough vitamin D to bind to them, function decreases and infections become more common.[7] Studies show that infection rates are higher in vitamin D deficiency. [7] Vitamin D is particularly important for respiratory health, as studies have shown that people with low vitamin D levels are much more likely to catch a cold or flu.[8]

Vitamin D and Autoimmune Response

Vitamin D may also play a role in autoimmunity, as vitamin D deficiency is common in autoimmune conditions such as multiple sclerosis and systemic lupus.[9] Vitamin D helps regulate the immune system by promoting an anti-inflammatory response over a pro inflammatory response, and may even affect gene transcription. [9] Larger, randomized controlled studies are needed to better understand the relationship between low vitamin D levels and autoimmunity.

Vitamin D Dosing

The adequate intake(AI) to maintain skeletal health is 400 IU. [6] The recommended dietary allowance for children and adults aged 1–70 years is 600 IU. [6] More vitamin D may be needed depending on personal vitamin D deficiency status as well as individual health concerns. Just as it is important to take enough vitamin D, it is also important to avoid taking too much vitamin D. The tolerable upper intake level (UL), the highest safe dose that can be taken without potential side effects, is 4000 IU (100 mcg) for adults aged 9 and up. [6] For immune support, some studies have used 1000–2000 IU per day, [10] though more may be needed depending on the degree of deficiency as determined by a vitamin D blood test and discussion with your health care provider. [13]

Learn More About Vitamin D

You can read why Vitamin D is Important here, and learn more about foods with vitamin D, the best sources of vitamin D, causes of deficiency, and how to choose the best vitamin D supplement to support immunity and overall health.

Maxine Fidler, ND

Maxine Fidler, ND

Maxine Fidler is a licensed naturopathic doctor who loves to write about natural health.

References :
  1. Swart KM, Lips P, Brouwer IA, et al. Effects of vitamin D supplementation on markers for cardiovascular disease and type 2 diabetes: an individual participant data meta-analysis of randomized controlled trials. Am J Clin Nutr. 2018; 107(6):1043-53.
  2. Mitri J, Pittas AG. Vitamin D and diabetes. Endocrinol Metab Clin North Am. 2014; 43(1):205-32.
  3. Spedding S. Vitamin D and depression: a systematic review and meta-analysis comparing studies with and without biological flaws. Nutrients. 2014; 6(4):1501-18.
  4. Gao XR, Chen YS, Deng W. The effect of vitamin D supplementation on knee osteoarthritis: A meta-analysis of randomized controlled trials. Int J Surg. 2017; 46:14-20.
  5. Roth DE, Abrams SA, Aloia J, et al. Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries. Ann N Y Acad Sci. 2018; 1430(1):44-79.
  6. Health Canada. Vitamin D and Calcium: Updated Dietary Reference Intakes - [Internet]. 2021 [cited 10 March 2021]. Available from:
  7. Aranow C. Vitamin D and the immune system. J Investig Med. 2011; 59(6):881-6.
  8. Martineau AR, Jolliffe DA, Greenberg L, et al. Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis. Health Technol Assess. 2019; 23(2):1-44.
  9. Yang CY, Leung PS, Adamopoulos IE, et al. The implication of vitamin D and autoimmunity: a comprehensive review. Clin Rev Allergy Immunol. 2013; 45(2):217-26.
  10. Marchisio P, Consonni D, Baggi E, et al. Vitamin D supplementation reduces the risk of acute otitis media in otitis-prone children. Pediatr Infect Dis J. 2013; 32(10):1055-60.
  11. Rees JR, Hendricks K, Barry EL, et al. Vitamin D3 supplementation and upper respiratory tract infections in a randomized, controlled trial. Clin Infect Dis. 2013; 57(10):1384-92.
  12. Li-Ng M, Aloia JF, Pollack S, et al. A randomized controlled trial of vitamin D3 supplementation for the prevention of symptomatic upper respiratory tract infections. Epidemiol Infect. 2009; 137(10):1396-1404.
  13. Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017; 356:i6583.


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