Vitamin D: Vital for the Immune System

By Dr. Todd Ferguson

While observing the Stay-at-Home order for your health and safety, there are a few self-care wellness habits about which you’ll need to be extra mindful.

At the top of this list, along with hydration and hand washing, is the maintenance of an ideal level of Vitamin D. Because Vitamin D is essential for optimizing your immune system’s response to infection, especially during a pandemic, a Vitamin D deficiency may greatly increase your body’s risk of infection.

Both Vitamin D deficiency and insufficiency increase risk of infection and increase risk of worse outcomes from an infection. This means that even if you are only slightly lacking enough of the essential vitamin, your body can be greatly affected. Someone with low levels of Vitamin D is 40% more likely to experience a respiratory infection than someone with optimal Vitamin D levels (Ginde et al. 2009). In addition, both Vitamin D deficiency and insufficiency increase risk of autoimmunity (the body’s immune responses against its own healthy cells and tissues). The good news is, with proper Vitamin D levels, the Vitamin D acts as a catalyst for antimicrobial peptides that have the capacity to directly kill pathogens within the body (Korf et al. 2014).

Estimates of prevalence of deficiency ranges from 40% to 80% across all populations, increasing in prevalence among those people with darker skin pigmentation. Some common reasons include insufficient sun exposure (particularly for those who are sheltering in place without access to the outdoors), low intake of Vitamin D-rich foods, poor digestive function, and poor liver or kidney function.  We have found deficiency very common in this area.  Even those frequently outside are commonly deficient.  The production of Vitamin D resulting from sun exposure varies greatly among individuals and due to our Northern location, the intensity of the sun is only great enough to stimulate significant production in June, July, August, and some of September.  Sunscreen also can block Vitamin D production.  Vitamin D is naturally occurring in the fat of many animal and fish products along with mushrooms.

Foods rich in Vitamin D include:

  • Salmon
  • Herring and Sardines
  • Whole milk and Butter
  • Eggs
  • Mushrooms
  • Cod and Cod liver oil
  • Halibut
  • Pork (if raised outdoors)

Why should you get tested for Vitamin D deficiency?

First of all, testing is necessary in order to establish whether or not you are deficient. Because individual responses to supplementation vary significantly, testing is the only way to ensure that optimal levels of Vitamin D are restored safely and without the toxic effects of too much Vitamin D. Testing is also important to establish maintenance levels given the variety of sun intensity in the summer and winter in our area.

During this unusual and stressful time, one of the best ways to establish resiliency is to maintain your bodily health. We are here to help. Please contact us if you have questions about the importance of maintaining your vitamin levels, particularly those like Vitamin D that have a strengthening effect on your immune system.

We at Prairie Naturopathic Doctors wish you wellness. Take care.



Ginde, A.A., J.M. Mansbach, C.A. Camargo Jr. 2009. “Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey.” Archives of Internal Medicine. 169(4):384-90. DOI: 10.1001/archinternmed.2008.560.

Korf, H., B. Decallonne, C. Mathieu. 2014. “Vitamin D for infections.” Current Opinion in Endocrinology, Diabetes and Obesity. 21(6):431-6. DOI: 10.1097/MED.0000000000000108.

Lang, P.O., R. Aspinall. 2017. “Vitamin D Status and the Host Resistance to Infections: What It Is Currently (Not) Understood.” Clinical Therapeutics. 39(5):930-945. DOI: 10.1016/j.clinthera.2017.04.004. Epub 2017 Apr 28.

Martens, P.J., C. Gysemans, A. Verstuyf, A.C. Mathieu. 2020. “Vitamin D's Effect on Immune Function.” Nutrients. 12(5). pii: E1248. DOI: 10.3390/nu12051248.

Parva, N. R., S. Tadepalli, P. Singh. 2018. “Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012).” Cureus. 10(6): e2741. DOI 10.7759/cureus.2741.

May 18, 2020

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