Efficacy of vitamin C in COVID-19 management: a systematic review and meta-analysis

COVID-19 has posed a global burden, with vitamin C considered a potential treatment due to its antioxidant, anti-inflammatory, and antimicrobial properties. However, its efficacy remains uncertain. This study aims to evaluate the impact of vitamin C supplementation on COVID-19 patients.

A comprehensive literature search was conducted across PubMed, MEDLINE, Embase, CBMdisc, WanFang Data, and CNKI from October 26, 2012, to October 1, 2023. The primary outcomes were 28-day mortality and in-hospital mortality, and the secondary outcomes were intensive care units (ICU) length of stay, duration of mechanical ventilation, length of vasopressor use, changes in SOFA score, and PaO₂/FiO₂ ratio. Random-effects models were employed to analyze the study outcomes. The Cochrane Systematic Review Guidelines and the GRADE system were utilized evaluated the risk of bias and the quality of evidence.

A total of thirteen studies were included with sample of 12,062. Most of these included studies exhibited low to indeterminate bias risk. The quality of evidence ranged from very low to moderate across in included studies. The overall results indicated that non-substantial favorable impacts were observed in short-term mortality (risk ratio [RR]: 0.92, 95% Confidence Interval [CI]: 0.72 to 1.17, P = 0.415) and in hospital mortality (RR: 1.05, 95% CI: 0.95 to 1.16, P = 0.286), nor other secondary clinical outcomes.

Although the current application of vitamin C in COVID treatment and management, our findings revealed that vitamin C did not significantly improve COVID outcomes. More high-quality and multicenter trials are required to further elucidate the association between vitamin C and COVID-19.

Registration of systematic reviews: This study was registered with the International Prospective Register of Systematic Reviews (PROSPERO), under the registration number CRD42024527599.