Vitamin C and COVID-19 treatment: A systematic review and meta-analysis of randomized controlled trials

Vitamin C has been used as an anti-oxidant in various diseases including viral illnesses like coronavirus disease (COVID-19). Meta-analysis of randomized controlled trials (RCT) investigating the role of vitamin C supplementation in COVID-19 was carried out. Total 6 RCTs including n = 572 patients were included. Vitamin C treatment didn't reduce mortality (RR 0.73, 95% CI 0.42 to 1.27; I2 = 0%; P = 0.27), ICU length of stay [SMD 0.29, 95% CI -0.05 to 0.63; I2 = 0%; P = 0.09), hospital length of stay (SMD -0.23, 95% CI -1.04 to 0.58; I2 = 92%; P = 0.57) and need for invasive mechanical ventilation (Risk Ratio 0.93, 95% CI 0.61 to 1.44; I2 = 0%; P = 0.76). Further sub-group analysis based on severity of illness (severe vs. non-severe), route of administration (IV vs. oral) and dose (high vs. low) failed to show any observable benefits. No significant benefit noted with vitamin C administration in COVID-19. Well-designed RCTs with standardized control group needed on this aspect. •Clinical benefit of vitamin C in COVID is controversial.•This meta-analysis did not show any major health related outcome benefit due to vitamin C supplementation.•Sub-group analysis based on dosage, route of administration and disease severity failed to show any observable benefit.