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Clin Infect Dis. 2019 Aug 17. pii: ciz801. doi: 10.1093/cid/ciz801. [Epub ahead of print]

Effect of monthly high-dose vitamin D supplementation on acute respiratory infections in older adults: A randomized controlled trial.

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Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
School of Population Health, University of Auckland, Auckland, NZ.
Department of Public Health and Primary Care, University of Cambridge, UK.
Department of General Practice, University of Otago, Christchurch, NZ.



Although adults with low vitamin D status are at increased risk of acute respiratory infection (ARI), randomized controlled trials of vitamin D supplementation have provided inconsistent results.


We performed a randomized, double-blinded, placebo-controlled trial of 5,110 adults, aged 50-84 years. In 2011-2012, participants were randomized to an initial oral dose of 200,000 IU vitamin D3 followed by 100,000 IU monthly (n=2,558) or placebo (n=2,552) until late 2013 (median follow-up 1.6 years). Participants reported upper and lower ARIs on monthly questionnaires. Cox models analyzed time to first ARI (upper or lower) by treatment group.


Participants' mean age was 66 years and 58% were male; 83% were of European/Other ethnicity, with the rest Maori, Polynesian or South Asian. Mean (SD) baseline blood 25-hydroxyvitamin D (25OHD) level was 63 (24) nmol/L; 25% were <50 nmol/L. In a random sample (n=441), vitamin D supplementation increased mean 25OHD to 135 nmol/L at 3 years, while those on placebo stayed at 63 nmol/L. During follow-up, 3,737 participants reported at least one ARI: 74.1% in the vitamin D group versus 73.7% in the placebo group. The hazard ratio for vitamin D compared to placebo was 1.01 (95%CI, 0.94, 1.07). Similar results were seen in most subgroups, including those with baseline 25OHD <50 nmol/L and in analyses of the upper/lower components of the ARI outcome.


Monthly high-dose vitamin D supplementation does not prevent ARI in older adults with a low prevalence of profound vitamin D deficiency at baseline. Whether effects of daily or weekly dosing differ requires further study.


Australian New Zealand Clinical Trials Registry, Identifier ACTRN12611000402943.


acute respiratory infection; adults; randomized controlled trial; supplement; vitamin D


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