Abstract
Reducing the risk of acute respiratory infections (ARIs) through vitamin D administration is a common preventive strategy used in routine clinical practice. However, the results of clinical trials are often controversial, which makes it necessary to summarize data available so far in order to develop more clear and well-founded clinical guidelines. Materials and methods. This meta-analysis was conducted to summarize the evidence on the preventive efficacy of vitamin D3 (cholecalciferol) against ARIs among adults using the results of randomized clinical trials (RCTs). The primary endpoint in all included studies was the absolute proportion of participants diagnosed with at least one ARI episode (upper/lower respiratory tract infections or infections of mixed locations) during the follow-up period. Results. We found that vitamin D3 intake (n = 11,276) was effective for preventing ARIs vs placebo (n = 10,955): in a random effects model, the odds ratio (OR) was 0.82 (95% confidence interval (CI): 0.69–0.98; p = 0.0355), whereas the number needed to treat (NNT) was 20.43 (between 10.70 and 255.67). There were no differences in efficacy between daily, weekly, or monthly intake of vitamin D3 (p = 0.7884). Given that 7 out of 13 studies included in this meta-analysis analyzed daily vitamin D3 intake and only 1 study assessed weekly intake, we can conclude that daily dosing, in general, has a broader evidence base. Conclusion. Thus, daily intake of D3 at a dose of ≥ 2000 IU/day (NNT = 20.43) was the most effective and studied strategy for preventing ARIs among adults. Key words: acute respiratory viral infections, influenza, COVID-19, nonspecific prevention, vitamin D3, colecalciferol
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