The aim of this review is to explore the available scientific literature and elucidate whether infections, including COVID-19, can cause hypovitaminoses, and on the other hand, may hypovitaminoses be the risk factor for the weaker immune response to infection. Methods include literature search (PubMed, ScienceOpen). Conclusion: optimal nutritional status, especially of vitamins A, C, E and D, is important for the normal functioning of the immune system. It seems that infections can increase the expenditure of vitamins A and C, and vice versa, lower levels of vitamin A and C may be associated with an increased susceptibility for infections and increased risk for the development of severe forms of infection, including COVID-19. Immunomodulatory vitamins D and E are important for the optimization of the immune response to various infections, protecting thus the host from both severe forms of infection and hyperinflammatory immune response with the development of cytokine storm and/or autoimmune processes, which is especially important in the context of COVID-19 pandemic. It seems that vitamin K deficiency is an important modifiable risk factor for the development of severe forms of COVID-19 and that vitamin D and vitamin K deficiency are interrelated, and represent potentially a synergistic effect on the severity of COVID-19.
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