Antioxidants and clinical outcomes of patients with coronavirus disease 2019: A systematic review of observational and interventional studies

Coronavirus disease 2019 (COVID‐19) is a newly emerging viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Oxidative stress appears to be a prominent contributor to the pathogenicity of SARS‐CoV‐2. Therefore, we carried out a systematic review of human observational and interventional studies to investigate the role of some antioxidants such as vitamins A, E, D, and C, selenium, zinc, and α‐lipoic acid in the main clinical outcomes of subjects with COVID‐19. Google Scholar, Cochrane Library, Web of Science, Scopus, and Medline were searched using Medical Subject Headings (MeSH) and non‐MeSH terms without restrictions. Finally, 36 studies for vitamins C and D, selenium, and zinc were included in this systematic review; however, no eligible studies were found for vitamins A and E as well as α‐lipoic acid. The results showed the promising role of vitamin C in inflammation, Horowitz index, and mortality; vitamin D in disease manifestations and severity, inflammatory markers, lung involvement, ventilation requirement, hospitalization, intensive care unit (ICU) admission, and mortality; selenium in cure rate and mortality; and zinc in ventilation requirement, hospitalization, ICU admission, biomarkers of inflammation and bacterial infection, and disease complications. In conclusion, it seems that antioxidants, especially vitamins C and D, selenium, and zinc, can improve multiple COVID‐19 clinical outcomes. Nevertheless, more studies are necessary to affirm these results.