Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials.

What this study found

Vitamin D supplementation modestly reduced the risk of having one or more acute respiratory infections compared with control. For the primary outcome, 14 332/23 364 participants (61.3%) in the vitamin D groups versus 14 217/22 802 (62.3%) in control had at least one ARI, with OR 0.92 (95% CI 0.86-0.99; 37 studies; I2=35.6%). Benefit was most evident with daily dosing, especially 400-1000 IU/day, and in participants aged 1.0-15.99 years; protection was not consistent across baseline 25(OH)D strata. Serious adverse events were not increased, and other secondary respiratory and safety outcomes…

Study & population

Systematic review and meta-analysis of 46 randomized controlled trials including 75 541 participants from 23 countries.

Intervention

Vitamin D supplementation was evaluated in a range of regimens, including daily, weekly, monthly, and combined bolus-plus-daily dosing.

Key limitation

There was substantial between-trial heterogeneity, and the authors noted possible publication bias.

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