The Role of Vitamin D in Infection

When it comes to infections, vitamin D holds an enviable place. The vitamin’s central role in immunity has been the topic of numerous scientific publications. We now know that vitamin D is an immunomodulatory hormone that increases the production of proteins used by immune cells to destroy and cripple invaders. This effect also occurs in the lungs which explains why studies show that vitamin D deficiency predisposes to respiratory infections.

Not only can vitamin D prevent infections in the first place, it also modulates the immune response to make it less likely that serious complications will develop once an infection has occurred.   Indeed, vitamin D prevents the production of immune inflammatory messengers and reduces the risk that the immune system will lose control and produce what is known as a “cytokine storm” – the uncontrolled and excessive release of inflammation producing compounds by immune cells.i

The effect of vitamin D on infections is likely profound and may explain the seasonal variability seen with the flu. In 1981, a researcher by the name of R. Edgar Hope-Simpson proposed that the seasonality of the influenza epidemic is likely caused by fluctuation in vitamin D levels associated with summer or winter sun exposure (vitamin D is produced in our skin when we are exposed to solar radiation).[i] Research shows that the influenza epidemic typically peaks two months on either side of the winter solstice, when vitamin D levels are at their lowest.  We know that vitamin D deficiency increases the risk of respiratory infections in children.[ii] International studies have also shown that vitamin D supplementation can reduce respiratory infections in school children.[iii]

Given the current pandemic, it is recommendable to have your vitamin D levels tested and your dose adjusted to obtain the maximal benefits associated with this important vitamin.[iv]


[i] Cannell et al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006 Dec; 134(6): 1129–1140.
[ii] Wayse V et al. Association of subclinical vitamin D deficiency with severe acute lower respiratory infection in Indian children under 5 y. European Journal of Clinical Nutrition. 2004;58:563–567.

[iii] Rehman PK. Sub-clinical rickets and recurrent infection. Journal of Tropical Pediatrics. 1994;40:58.

[iv] Grant WB et al. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020 Apr 2;12(4):988

Ludovic Brunel, Naturopathic Doctor

Dr. Ludovic Brunel graduated with a degree in Human Nutrition from McGill University in Montreal and pursued his studies in Naturopathic Medicine at the Canadian College of Naturopathic Medicine in Toronto.

2 Responses to “The Role of Vitamin D in Infection”

  1. What would be a good range of vitaman D3 for an adult. I take 3000 daily. Should I be upping this as winter is upon us. Also how imprortment is zinc and Vitamin C. We also supplement with this. We have on hand eldberry juice although there was some initial concerns about potential cytokine storms with elderberry juice. I have heard conflicting information this. What are your thoughts. I have a good stock of oil of oregano and other remedies and we are trying to eat health, exercise and not stress about this which is hard. My husband who is overweight, 67 years old and has some minor heart concerns along with type one diabetes, started the Keto diet and has lost weight and feel much better. Thanks Sylvia Doctor Meaghan patient.

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