Table 4.

Studies investigating the effect of oral vitamin C in patients with COVID-19.

Population Mean Age Location	Intervention Duration	Findings (Vitamin C vs. Control)	Reference
Randomised Controlled Trials
214 patients with SARS-CoV-2 Age = 45 ± 15 years Ohio and Florida, USA	8 g/day oral vitamin C or 50 mg/day zinc gluconate or vitamin C + zinc gluconate or standard care (n = 48–58 per group) for 10 days	18% (1.2 day) decrease in time to 50% reduction of symptoms (p = 0.38) Vitamin C increased the rate of recovery by 71% (p = 0.036)	[38]
			[39]
72 non-serious hospitalised patients Mean age = 36 years Isfahan, Iran	1000 mg/day oral vitamin C (plus 400 IU/day vitamin E) or standard care (n = 34–38 per group) until hospital discharge or ICU admission	No differences in clinical improvement or duration of hospitalisation (p = 0.82) No patients died in the study	[40]
Retrospective cohort study
296 critically ill patients Age = 61 ± 15 Riyadh, Saudi Arabia	1000 mg/day oral vitamin C or standard care (n = 148 per group) for approx. 11 days	No association with hospital or 30-day mortality, or organ injury Longer ICU and hospital length of stay Decreased incidence of thrombosis (6 vs. 13%, OR 0.42 [0.18–0.94], p = 0.03)	[41]