A role for vitamin D supplementation in the prevention of upper respiratory tract infections?

Christine Ma, Faculty of Medicine, University of New South Wales, Sydney, Australia

Upper Respiratory Tract Infections (URTIs) are a leading cause of sickness and loss of productivity amongst adults and school-aged children [1]. Vitamin D has been shown to play a role in a variety of respiratory diseases, including asthma, COPD, malignancy and infectious diseases – although the mechanism for these is largely unclear [2]. Retrospective and observational studies have pointed toward an inverse relationship between serum levels and the incidence of URTIs, however large prospective trials have shown conflicting evidence for the efficacy of Vitamin D in preventing these infections [2, 3].

A randomised, double-blind, placebo-controlled trial in Christchurch, New Zealand investigated the effects of high-dose Vitamin D supplementation on the frequency of URTIs across a healthy adult population. There were a total of 322 participants, the treatment group was given a loading dose of oral Vitamin D and 18 100000IU monthly doses. Participants were asked to report episodes of URTIs and a nasopharyngeal swab was collected for confirmation. The primary outcome was the number of reported URTI episodes with secondary outcomes encompassing their severity and impact on productivity.

The study found no statistically significant differences amongst the two groups in primary or secondary end-points, with similar numbers of URTIs as well as similar impacts as assessed by questionnaires. This is in line with previous studies in adults. The study’s main strengths lay in its large sample size, and high dose of Vitamin D. However it studied a relatively healthy population within one area, whom all had adequate levels of serum Vitamin D [4]. Further directions for research include investigation of this therapy in the paediatric population – where previous studies have shown a 50% reduction in URTIs with Vitamin D supplementation – or in populations with Vitamin D deficiency, where an effect may be more readily observed.

References: 

1. Huestn WJ, Casey BR. Respiratory Problems. CURRENT Diagnosis & Treatment in Family Medicine, 3 ed. New York: McGraw Hill; 2011.
2. Herr C, Greulich T, Koczulla RA, Meyer S, Zakharkina T, Branscheidt M, Eschmann R, Bals R. The Role of Vitamin D in Pulmonary Disease: COPD, asthma, infection, and cancer: Review. Respiratory Research 2011; 12(31) doi:10.1186/1465-9921-12-31
3. Laaksi I, Ruohola JP, Tuohimaa P, Mattila V, Auvinen A, Ylikomi T, Pihlajamaki H. An association of serum vitamin D concentrations <40nmol/L with acute respiratory tract infection in young Finnish men. American Journal of Clinical Nutrition. 2007; 86(3): 714-717. http://ajcn.nutrition.org/content/86/3/714.full
4. Murdoch DR, Slow S, Chambers ST, Jennings LC, Stewart AW, Priest PC, Florkowski CM, Livesey JH, Camargo CA, Scragg R. Effect of Vitamin D Supplementation on Upper Respiratory Tract Infections in Healthy Adults. JAMA. 2012; 308(13):1333-1339 doi:10.1001/jama.2012.12505

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