Vitamin D for prevention of respiratory tract infections: A systematic review and meta-analysis

Objectives: To explore the effect of vitamin D supplementation in prevention of respiratory tract infections on the basis of published clinical trials. Materials and Methods: Clinical trials were searched from various electronic databases. Five clinical trials were suitable for inclusion. Outcome was events of respiratory tract infections in vitamin D group and placebo group. Data was reported as odds ratio with 95% confidence interval. Both random and fixed model was used for analysis. Analysis was done with the help of Comprehensive meta- analysis software 2. Results: Events of respiratory tract infections were significantly lower in vitamin D group as compared to control group [Odds ratio = 0.582 (0.417 - 0.812) P = 0.001] according to random model. Results were similar in fixed model. On separate analysis of clinical trials dealing with groups of children and adults, beneficial effect of vitamin D was observed in both, according to fixed model [Odds ratio = 0.579 (0.416 - 0.805), P = 0.001 and Odd ratio = 0.653 (0.472 - 0.9040, P = 0.010 respectively]. On using random model beneficial effect persisted in children's group but became nonsignificant in adults group [Odds ratio = 0.579 (0.416 - 0.805), P = 0.001 and Odd ratio = 0.544 (0.278 - 1.063) P = 0.075 respectively]. Conclusion: Vitamin D supplementation decreases the events related to respiratory tract infections. There is need of more well conducted clinical trials to reach to a certain conclusion.