Abstract

The COVID-19 pandemic has emerged as a major global health crisis. Vitamin D, a crucial fat-soluble vitamin, has been recommended for COVID-19 patients, though evidence of its effectiveness is inconsistent. This systematic literature review and meta-analysis aimed to evaluate the impact of vitamin D supplementation on COVID-19-related outcomes. A comprehensive search was conducted across PubMed, Scopus, Web of Science, Embase, and Cochrane databases. Primary outcomes included mortality and hospital length of stay, while secondary outcomes encompassed C-reactive protein (CRP), ferritin, D-dimer, hemoglobin (Hb) concentrations, and lymphocyte, neutrophil, and platelet counts. Data analysis was performed using Stata™ Version 14. A total of 16 trials were analyzed. The meta-analysis revealed that vitamin D supplementation significantly reduced hospital length of stay (mean difference = −1.16; 95 confidence interval CI: −2.23, −0.09; p =.033) with significant heterogeneity (I2 = 69.2%, p =.002). Subgroup analysis showed a more pronounced reduction in studies with vitamin D dosages ≤10 000 international units (IU) (mean difference = −1.27; 95% CI: −1.96, −0.57; p <.001) and in patients over 60 years old (mean difference = −1.84; 95% CI: −2.53, −1.14; p <.001). Additionally, vitamin D significantly reduced CRP concentrations in older adults (>60 years) (mean difference = −1.13; 95% CI: −2.07, −0.18; p =.019). No significant changes were found in ferritin, D-dimer, Hb concentrations, or in lymphocyte, neutrophil, and platelet counts (p >.05). In conclusion, while vitamin D supplementation did not significantly affect most COVID-19-related biomarkers, however, it reduces the length of hospital stay. © 2024 The Author(s). Pharmacology Research & Perspectives published by British Pharmacological Society and American Society for Pharmacology and Experimental Therapeutics and John Wiley & Sons Ltd.