Vitamin C for the management of COVID-19: a systematic review and meta-analysis of randomized controlled trials

Background: Vitamin C is a vital nutrient that functions as an antioxidant and is important as a co-factor and regulator of several immune system pathways. The role of vitamin C in the treatment of COVID-19 is largely debatable. We conducted this meta-analysis to evaluate the efficacy and safety of vitamin C in the treatment of COVID-19. Methods: We searched several electronic databases from inception to March 2023 to retrieve randomized controlled trials on the use of vitamin C for COVID-19. RevMan 5.4 was used to calculate risk ratios (RRs) and mean differences (MDs) along with confidence intervals (95% CI) using a random-effects model. Results: We included nine randomized controlled trials in our meta-analysis. Vitamin C did not reduce the all-cause mortality in patients with COVID-19 compared to the standard treatment (RR 0.92, 95% CI: 0.83–1.02; I 2 = 1%). Vitamin C was found to be associated with a similar incidence of ventilation in COVID-19 patients when compared to standard treatment (RR 0.98, 95% CI: 0.87–1.11, I 2 = 0%). There were no significant differences between both groups regarding the incidence of hospitalization (RR 1.00, 95% CI: 0.98–1.02; I 2 = 0%), incidence of recovery (RR 1.57, 95% CI: 0.45–5.50; I 2 = 52%), hospital mortality (RR 0.68, 95% CI: 0.44–1.06; I 2 = 0%) and length of hospital stay (MD −0.63, 95% CI: −3.04 to 1.78; I 2 = 81%). Conclusion: Vitamin C administration did not reduce all-cause mortality in COVID-19 patients. Additional studies are required to evaluate the role of vitamin C in the prevention and treatment of COVID-19 especially in ICU patients.