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Low vitamin D levels are associated with excess risk for upper respiratory tract infections (URTIs), but clinical trials of supplementation have been small and inconclusive. In a New Zealand–based study, researchers randomized 322 healthy adults (mean baseline 25-hydroxyvitamin D level, 29 ng/mL) to monthly oral vitamin D3 supplementation (200,000 IU for 2 months, followed by 100,000 IU for 16 months) or placebo. Participants reported no substantial previous vitamin D use.
Ninety-one percent of participants were followed for 18 months. Mean 25-hydroxyvitamin D levels increased to 50 ng/mL in the intervention group and remained unchanged in the placebo group. The incidence of URTIs during the study was similar in each group (mean, 3.7 episodes per person), as was URTI severity.
Murdoch DR et al. Effect of vitamin D3 supplementation on upper respiratory tract infections in healthy adults: The VIDARIS randomized controlled trial. JAMA 2012 Oct 3; 308:1333. (http://dx.doi.org/10.1001/jama.2012.12505)
Linder JA. Vitamin D and the cure for the common cold. JAMA 2012 Oct 3; 308:1375. (http://dx.doi.org/10.1001/jama.2012.13130)
Comment
An editorialist notes the long list of agents and approaches that have failed to prevent URTIs, including Echinacea, zinc, steam inhalation, vitamin C, and garlic. Vitamin D has just joined that list — at least for people whose baseline vitamin D status seems to be adequate.