Does Vitamin D Lower Risk for Acute Respiratory Infections?

Several years ago, a meta-analysis of 43 trials with 48,000 patients showed a modestly lower incidence of acute respiratory infections in patients who took vitamin D supplements compared with those who took placebo supplements (odds ratio, 0.92; 95% confidence interval, 0.86–0.99). The protective effect was independent of baseline vitamin D status and strongest in trials that involved daily doses of 400 to 1000 IU of vitamin D, had durations of 12 months or shorter, and enrolled children or adolescents (age range, 1–15 years; Lancet Diabetes Endocrinol 2021; 9:276).

The authors of that meta-analysis have updated their analysis, adding data from three recent randomized trials with an additional 16,000 patients. In the new meta-analysis, diffe…