Does vitamin D reduce the mortality rate of Plasmodium infection?: a systematic review and meta-analysis

BACKGROUND: Vitamin D supplementation is recommended as an effective adjunct to counteract malaria pathogenesis, but the evidence on this point is limited and controversial. This systematic review and meta-analysis aimed to investigate the effect of vitamin D administration on the survival rate of Plasmodium-infected animals in experimentally-induced malaria on days 6 and 10 post-infection. METHODS: Five electronic databases were searched up to 20 December 2021. The pooled risks ratio (RR) and associated 95% confidence interval were estimated using the Restricted-maximum likelihood (REML) random-effects model. Heterogeneity was assessed by Cochran’s Q test and I(2) value. Sub-group analyses were used to identify the sources of heterogeneity for several variables, such as type of vitamin D, type of intervention, and dose of vitamin D. RESULTS: Out of 248 articles found in the electronic database, six were eligible for inclusion in the meta-analysis. The current study found that the pooled random effect of risks ratio favored a statistically significant effect of vitamin D administration on survival rate in infected mice on day 6 post Plasmodium infection (RR = 1.08, 95%CI 1.03, 1.15, p < 0.99; I(2) = 0%). It also found that vitamin D administration significantly affected the survival rate on day 10 post-infection (RR = 1.94, 95%CI 1.39, 2.71, p < 0.001; I(2) = 69.02%). Subgroup analyses demonstrated a significant pooled RRs of the positive effect of vitamin D administration for cholecalciferol (RR = 3.11, 95%CI 2.41, 4.03, p < 0.001; I(2) = 0%), doses higher than 50 µg/kg (RR = 3.37, 95%CI 2.55, 4.27, p < 0.001; I(2) = 0%), and oral administration (RR = 3.01, 95%CI 2.37, 3.82, p < 0.001; I(2) = 0%). CONCLUSION: This systematic review and meta-analysis showed that vitamin D administration positively affects the survival rate in Plasmodium-infected mice. Since, the mouse model may not accurately reproduce the clinical and pathological features of human malaria, future research should investigate the impact of vitamin D in human malaria. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12936-023-04612-4.