Efficacy of vitamin D supplementation in the treatment of patients with COVID-19: a systematic review and meta-analysis of randomized controlled trials

Context: COVID-19 has substantial effects on respiratory health and overall well-being. Recent studies suggest vitamin D as a potential treatment, but the results are inconclusive.

Objective: The authors conducted a systematic review of randomized controlled trials (RCTs) to examine the link between vitamin D and patients with COVID-19.

Data sources: The authors searched electronic databases PubMed, Cochrane, CINAHL, EMBASE and Google Scholar from their inception till August 2023.

Study selection: Inclusion criteria used in our systematic review include: (1) patients who tested positive for COVID-19, (2) intervention was vitamin D supplementation, (3) the comparator was either a placebo, standard care of treatment, or, no treatment, (4) at least one of the clinical outcomes of interest were investigated, (5) study design being RCTs.

Data extraction: Two independent reviewers manually extracted information from selected articles, including study characteristics, patient characteristics, and the primary outcomes: all-cause mortality, ICU and hospital stay length and secondary outcomes: mechanical ventilation, supplemental oxygen, ICU admission, and adverse events. Risk ratios or mean differences and 95% CIs were calculated using a random-effects model.

Data synthesis: The authors' analysis included 14 RCTs with 2165 patients. Vitamin D significantly reduced ICU admissions and lowered the need for mechanical ventilation compared to placebo. However, it did not significantly affect hospital stay length, ICU stay length, mechanical ventilation duration, mortality, or the need for supplemental oxygen.

Conclusion: Vitamin D does not significantly improve certain clinical outcomes, such as hospital and ICU stay length, for patients with COVID-19. However, it still may be significantly beneficial in decreasing the burden on intensive care services.