Efficacy of Vitamin D Supplements in Treatment of Acute Respiratory Infection: A Meta-Analysis for Randomized Controlled Trials.

BACKGROUND: Recent randomized controlled trials (RCTs) have reported inconsistent findings regarding the efficacy of vitamin D supplementation in the treatment of acute respiratory infections (ARIs). This study aimed to investigate the efficacy of vitamin D supplementation in the treatment of ARIs using a meta-analysis of RCTs. METHODS: PubMed, EMBASE, and the Cochrane Library were searched for relevant articles in June 2021. Two of the authors independently assessed the eligibility of the trials. RESULTS: Out of 390 articles retrieved from the databases, we included 18 RCTs, which involved 3648 participants, with 1838 in an intervention group and 1810 in a control group in the final analysis. In the meta-analysis of all the trials, vitamin D supplements had a beneficial effect in the treatment of ARIs (relative risk (RR) = 1.07; 95% confidence interval (CI), 1.01-1.13; I2 = 66.9%). Publication bias was observed in the funnel plot. In the subgroup meta-analysis of high-quality RCTs, no significant efficacy of vitamin D supplements was found (RR = 1.02; 95% CI, 0.98-1.06; I2 = 24.0%). Although statistically significant changes of 7% in the treatment effects were observed, they are not considered as clinically substantial ones. CONCLUSIONS: The current meta-analysis suggests that vitamin D supplements are not clinically effective in the treatment of ARIs.

Efficacy of Vitamin D Supplements in Prevention of Acute Respiratory Infection: A Meta-Analysis for Randomized Controlled Trials.

BACKGROUND: Previous systematic reviews and meta-analyses of randomized controlled trials (RCTs) have reported inconsistent results regarding the efficacy of vitamin D supplements in the prevention of acute respiratory infections (ARIs). METHODS: We investigated these efficacy results by using a meta-analysis of RCTs. We searched PubMed, EMBASE, and the Cochrane Library in June 2021. RESULTS: Out of 390 trials searched from the database, a total of 30 RCTs involving 30,263 participants were included in the final analysis. In the meta-analysis of all the trials, vitamin D supplementation showed no significant effect in the prevention of ARIs (relative risk (RR) 0.96, 95% confidence interval (CI) 0.91-1.01, I2 = 59.0%, n = 30). In the subgroup meta-analysis, vitamin D supplementation was effective in daily supplementation (RR 0.83, 95% CI, 0.73-0.95, I2 = 69.1%, n = 15) and short-term supplementation (RR 0.83, 95% CI, 0.71-0.97, I2 = 66.8%, n = 13). However, such beneficial effects disappeared in the subgroup meta-analysis of high-quality studies (RR 0.89, 95% CI, 0.78-1.02, I2 = 67.0%, n = 10 assessed by the Jadad scale; RR 0.87, 95% CI, 0.66-1.15, I2 = 51.0%, n = 4 assessed by the Cochrane's risk of bias tool). Additionally, publication bias was observed. CONCLUSIONS: The current meta-analysis found that vitamin D supplementation has no clinical effect in the prevention of ARIs.