Therapeutic effects of high-dose vitamin C supplementation in patients with COVID-19: a meta-analysis

Context Coronavirus disease 2019 (COVID-19) could induce the "cytokine storm" due to overactivation of immune system and accompanied by acute respiratory distress syndrome as a serious complication. Vitamin C has been effective in improving lung function of patients by reducing inflammation.Objective The aim was to explore the therapeutic effects of high-dose vitamin C supplementation for patients with COVID-19 using meta-analysis.Data Sources Published studies were searched from PubMed, Cochrane Library, Web of Science, EMBASE, and China National Knowledge Infrastructure databases up to August 2022 using the terms "vitamin C" and "COVID-19". Data analyses were performed independently by 2 researchers using the PRISMA guidelines.Data Extraction Heterogeneity between the included studies was assessed using I2 statistics. When I2 & GE;50%, the random-effects model was used; otherwise, a fixed-effects model was applied. Stata 14.0 software was used to pool data by standardized mean differences (SMDs) with 95% CIs or odds ratios (ORs) with 95% CIs.Data Analysis The 14 studies had a total of 751 patients and 1583 control participants in 7 randomized controlled trials and 7 retrospective studies. The vitamin C supplement significantly increased ferritin (SMD = 0.272; 95% CI: 0.059 to 0.485; P = 0.012) and lymphocyte count levels (SMD = 0.376; 95% CI: 0.153 to 0.599; P = 0.001) in patients with COVID-19. Patients administered vitamin C in the length of intensive care unit staying (SMD = 0.226; 95% CI: 0.073 to 0.379; P = 0.004). Intake of vitamin C prominently alleviate disease aggravation (OR = 0.344, 95%CI: 0.135 to 0.873, P = 0.025).Conclusions High-dose vitamin C supplementation can alleviate inflammatory response and hinder the aggravation of COVID-19.