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Strengthening Immunity with Vitamin D

Narinder Duggal, MD, FRCPC

Numerous studies have demonstrated that vitamin D strengthens our overall immunity and helps prevent bacterial and viral infections. Generally, our immune system protects us in two ways; adaptive and innate.¹ Adaptive immunity, as the name suggests, fights against infections the body has previously encountered.  Innate immunity protects us from new infections which the body has never encountered in the past. For prevention of diseases like influenza or H1N1 flu, which presents in a new mutated form every year, our innate and adaptive immune system has to be healthy and strong.

 Vitamin D not only helps enhance the functioning of the adaptive immune system but also stimulates the innate immune system through the vitamin D cellular receptors.² The stimulated cells of the immune system produce antimicrobial peptides (AMP’s), which have antiviral as well as antimicrobial properties.³  Our respiratory tract is lined with cells, which have the vitamin D receptors and once stimulated release AMPs. The seasonal winter drop in vitamin D levels due to lack of sunlight is believed to be the reason  for outbreaks of influenza and other respiratory infections in winters.⁴

“Vitamin D deficiency is directly related to respiratory infections in the winter’’ says Dr. Dowd in his book ‘The Vitamin D Cure’.⁵ The relationship between vitamin D levels and respiratory infections is also supported by AA Ginde’s analysis of data from the Third National Health and Nutrition Examination Survey (NHANES III) collected from 1988 to 1994.The analysis concluded that the subjects having less than 10 ng/ml of 25(OH) vitamin D were 40% more susceptible to respiratory infections than those with 30 ng/ml or higher. A secondary analysis of the same data confirmed that upper respiratory tract infections were reported more often by subjects with lower vitamin D levels.⁶ 

Scientific research indicates that 25(OH) vitamin D levels are inversely related to lower respiratory tract infections.  A 2007 study involving 800 military men in Finland found that subjects with serum 25(OH)Vitamin D concentrations less than 40 nmol/L  had more absent days from duty due to respiratory infections.⁷ A 2009 study found that apparently healthy newborns, with vitamin D deficiency, had an increased risk of suffering from respiratory tract infections.⁸  Medical literature is filled with similar data demonstrating Vitamin D’s role in enhancing the body’s defense to fight respiratory infections.

A natural experiment reported by Dr. J.J. Canell indicates that vitamin D can prevent influenza.⁹ Subjects for this study were long-term care behavioral health patients who were on vitamin D supplementation for several months. During an influenza outbreak, patients in other units of the same hospital were infected but none of the patients receiving vitamin D supplements in the behavioral health unit got infected. The study hypothesized the possible role of vitamin D supplementation to strengthen the immunity against influenza.

It is interesting to learn that older studies also reported the correlation between sun exposure and respiratory infections, but interpreted it differently. A 1981 Hope –Simpson article documented the relationship between the prevalence of seasonal flu and solar radiations, which was interpreted as ‘seasonal stimulus’4. Now we know that the seasonal stimulus is, in fact, related to production and storage of Vitamin D.


References:

1.    http://uhaweb.hartford.edu/BUGL/immune.htm. (Open link)
2.    Adorini L, Penna G. Control of autoimmune diseases by the vitamin D endocrine system. Nat Clin Pract Rheumatol 2008;4(8):404-12. (PUBMED Abstract)
3.    Bartley J. Vitamin D, innate immunity and upper respiratory tract infection. J Laryngol Otol:1-5. (PUBMED Abstract)
4.    Cannell JJ, Vieth R, Umhau JC, et al. Epidemic influenza and vitamin D. Epidemiol Infect 2006;134(6):1129-40. (PUBMED Abstract)
5.    http://www.thevitamindcure.com/dr-dowd/. (Open link)
6.    Ginde AA, Mansbach JM, Camargo CA, Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med 2009;169(4):384-90. (PUBMED Abstract)
7.    Laaksi I, Ruohola JP, Tuohimaa P, et al. An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men. Am J Clin Nutr 2007;86(3):714-7. (PUBMED Abstract)
8.    Karatekin G, Kaya A, Salihoglu O, et al. Association of subclinical vitamin D deficiency in newborns with acute lower respiratory infection and their mothers. Eur J Clin Nutr 2009;63(4):473-7. (PUBMED Abstract)
9.    http://www.medicalnewstoday.com/articles/51913.php. (Open link)