Vitamin A and vitamin E in SARS-CoV-2 Infection: a systematic review

Abstract It is known that nutrition plays an important role in maintaining the immune system. In addition, viral infections can culminate in the depletion of vitamins, such as vitamins A and E, and inadequate levels of nutrients can be harmful to health, it is important to verify its relationship with COVID-19, a disease caused by the SARS-CoV-2, the new coronavirus first identified in Wuhan (China), and has spread rapidly worldwide, affecting the immune system and causing exacerbated inflammation. The aim of the study is to investigate whether COVID-19 affects the levels of these vitamins, and how they can help fighting the infection, it is relevant since they can be included as therapy against the disease. A systematic search was performed according to the PRISMA statement, using the PubMed, Web of Science, and EMBASE databases. We selected articles that presented the controlled descriptors present in the title or abstract without language exclusion. Abstracts, conferences, editorials, book chapters, review articles, letters, short communications, supporting information, or articles unavailable for download were excluded. The quality of studies was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). From a total of 4,572 articles, 10 met all inclusion criteria. Three of them were related with vitamin A, two with vitamin E and five relating both vitamins to COVID-19. Of these, 70% were studies that evaluated the concentrations of vitamins, and 30% that evaluated the impact of supplementation of these micronutrients. Adult and elderly patients had decreased vitamin A and E concentrations, being below or close to the reference values for deficiency, especially in critical patients. Supplementation of these vitamins was associated with better prognosis of patients. However, the therapeutic capacity of these vitamins requires additional biological validation through more robust studies, such as randomized clinical trials and assessment of food intake of these vitamins. In addition, studies that assess serum levels of these vitamins before infection are also required.