The role of vitamin D deficiency on the Covid-19: A systematic review and meta-analysis of observational studies

Kaya, Mehmet Onur; Pamukçu, Esra; Yakar, Burkay

Objectives: Although vaccination has started, it seems that Covid-19 will continue to threaten public health for a long time. Therefore, in addition to the vaccine, the use of supplements to support the immune system may also be important. The main purpose of this study is to indicate the possible effect of low serum vitamin D (25(OH)D<20 ng/mL or 50nmol/L) on the Covid-19 infection and outcomes. Methods: To accomplish our objectives, we searched on Google Scholar, PubMed, Scopus, Web of Science, and ScienceDirect databases without any language restrictions for articles between 01.01.2020 and 15.12.2020. We performed three meta-analyses to combine the OR values by paying attention to laboratory measurement units for vitamin D and the measured serum 25(OH)D level. Results: 23 eligible studies involving the relationship between vitamin D and Covid-19 infection/outcomes were identified (n=206861). We applied three meta-analyses called D-CIMA, D-CSMA and D-CMMA for Covid-19 infection, severity, and mortality, respectively. According to obtained result from D-CIMA, one which has low serum vitamin D are 1.64 times (95%CI=[1.32-2.04],p<0.001) more likely to get Covid-19 infection. In D-CSMA, we found that people with the serum 25(OH)D level below 20ng/mL or 50nmol/L have 2.58 times (95%CI=[1.28-5.19],p=0.008) more likely to risk having severe Covid-19. We obtained from D-CMMA that low vitamin D level has no effect on Covid-19 mortality (OR=2.42 95%CI=[0.73-8.04],p=0.148). Conclusion: Vitamin D deficiency increases the risk of Covid-19 infection and the potential for the severity of the disease. Therefore, vitamin D supplements should be added to prevention and treatment protocols for Covid-19 disease.