Vitamin D and respiratory tract infections
||This article needs more medical references for verification or relies too heavily on primary sources. (October 2012)|
A link between vitamin D and respiratory tract infections has been hypothesised. According to the hypothesis, vitamin D deficiency may predispose to infection. Evidence supporting the hypothesis derives from some scientific studies and the observation that outbreaks of respiratory infections occur predominantly during months associated with lower exposure to the sun. Evidence against the hypothesis has also been reported. The Institute of Medicine concluded in a 2011 report that the existing data were "not consistently supportive of a causal role" for the vitamin in reducing the risk of infection.
Ultraviolet radiation and vitamin D
An inverse association between exposure to the sun and upper respiratory tract infections was first proposed in 1926 by Smiley, who theorized that seasonality of infection was caused by “disordered vitamine metabolism in the human...directly due to a lack of solar radiation during the dark months of winter.”1 Studies of Dutch2 and Russian3 subjects have also indicated a correlation of ultraviolet light exposure and relative absence of infection. However, the seasonality of infections such as influenza may also be explicable by other factors. For example, low absolute humidity favours the survival of the influenza virus.4A review by authors from the University of Maryland School of Pharmacy suggested that while low-dose vitamin D supplementation was unlikely to be harmful, "sensible sun exposure" was "an inexpensive and enjoyable way" to ensure healthy levels of vitamin D.5
Evidence both for and against an association of vitamin D and respiratory infections has been reported. Early studies of vitamin D and mice came to different conclusions, with one group reporting a link and the other no link between deficiency and infection.5 More recent studies of humans have also had divergent results. A study published in the Archives of Internal Medicine found that people with the lowest blood vitamin D levels reported having significantly more recent colds or cases of the flu chronic respiratory disorders, especially those who had pre-existing respiratory ailments.67 A report in the American Journal of Clinical Nutrition reported that children who took vitamin D3 supplements daily in winter were 42% less likely to get infected with seasonal flu than those who were given a placebo.89 Mongolian schoolchildren who drank vitamin D fortified milk during winter reported having fewer colds than those who received non-fortified milk.10 Another study found no effect of vitamin D supplementation on the incidence or severity of upper respiratory tract infections.11 Authors of one of the positive studies also stressed that their results would need to be confirmed in clinical trials before vitamin D could be recommended to prevent infections.6
The Institute of Medicine released a comprehensive, peer-reviewed report on calcium and vitamin D in 2011. The conclusion of the report was that the existing studies did not provide strong or consistent evidence for a link between vitamin D deficiency and respiratory tract infections. The authors stated that data from randomised controlled trials would be needed, showing a dose response to vitamin D supplementation, before recommendations could be considered.12
Vitamin D supplementation
Proponents of the vitamin D hypothesis have recommended dietary supplements of (5,000 International Units (IU)/day for adults and 1,000 IU/day for every 25 pounds of body weight in children) and suggested that larger doses (2,000 IU/kg/day for 3–4 days) could be used to treat influenza.1314 It has been noted that large doses of vitamin D can lead to hypercalcemia and that "single megadoses" of vitamin D, while not especially harmful, may be associated with an increased risk of bone fractures.5 The authors of this review suggested that supplementation should be offered only to those with verified deficiencies or to promote muscular and skeletal health in elderly patients.5
- Termorshuizen F, Wijga A, Gerritsen J, Neijens HJ, van Loveren H (October 2004). "Exposure to solar ultraviolet radiation and respiratory tract symptoms in 1-year-old children". Photodermatol Photoimmunol Photomed 20 (5): 270–1. doi:10.1111/j.1600-0781.2004.00110.x. PMID 15379879.
- Shaman J, Kohn M (March 2009). "Absolute humidity modulates influenza survival, transmission, and seasonality". Proc. Natl. Acad. Sci. U.S.A. 106 (9): 3243–8. doi:10.1073/pnas.0806852106. PMC 2651255. PMID 19204283.
- Ginde AA, Mansbach JM, Camargo CA (February 2009). "Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey". Arch. Intern. Med. 169 (4): 384–90. doi:10.1001/archinternmed.2008.560. PMID 19237723.
- food consumer newsite http://www.foodconsumer.org/newsite/2/other_diseases/vitamin_d_as_effective_as_vaccine_in_preventing_flu_1403100231.html
- Camargo et al. (August 2012). "Randomized Trial of Vitamin D Supplementation and Risk of Acute Respiratory Tract Infection in Mongolia.". Pediatrics. PMID 22908115.
- DIETARY REFERENCE INTAKES FOR CALCIUM AND VITAMIN D Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board. A. Catharine Ross, Christine L. Taylor, Ann L. Yaktine, and Heather B. Del Valle, Editors. Institute of Medicine of the National Academies, 2011.
- Cannell JJ, Zasloff M, Garland CF, Scragg R, Giovannucci E (2008). "On the epidemiology of influenza". Virol. J. 5: 29. doi:10.1186/1743-422X-5-29. PMC 2279112. PMID 18298852.
See also VitaminDWiki
- Vitamin D and Respiratory Tract Infections – meta-analysis with charts June 2013
- Pneumonia 2.6X more likely if low vitamin D – April 2013
- Respiratory infections reduced by 63 percent with 4000 IU vitamin D daily - RCT Dec 2012
- Vitamin D reduces respiratory tract infections by 40 percent– meta-analysis Dec 2012