Kefir: A protective dietary supplementation against viral infection.

Mode of action of kefir supplementary dietary against viral infection. • Kefir and kefir derivatives can suppress viral activity by modulating immune-system responses and/or causing disruption of viral adhesion. • The antiviral mechanisms of kefir involve enhancement of macrophage production and boosting the activity of proinflammatory cytokines. • Kefir dietaries have anti-inflammatory activity by inhibiting the activity of proinflammatory cytokines such as IL-1β, TNF-α and IL-6. • Using kefir (and its byproducts) as an inhibitor of expression of proinflammatory cytokines in COVID-19 patients could be a viable policy. Coronavirus disease 2019 (COVID-19) is an infectious disease caused by a recently discovered coronavirus termed 'severe acute respiratory syndrome coronavirus 2′ (SARS-CoV-2). Several scholars have tested antiviral drugs and compounds to overcome COVID-19. 'Kefir' is a fermented milk drink similar to a thin yogurt that is made from kefir grains. Kefir and its probiotic contents can modulate the immune system to suppress infections from viruses (e.g., Zika, hepatitis C, influenza, rotaviruses). The antiviral mechanisms of kefir involve enhancement of macrophage production, increasing phagocytosis, boosting production of cluster of differentiation-positive (CD4+), CD8+, immunoglobulin (Ig)G+ and IgA+ B cells, T cells, neutrophils, as well as cytokines (e.g., interleukin (IL)-2, IL-12, interferon gamma-γ). Kefir can act as an anti-inflammatory agent by reducing expression of IL-6, IL-1, TNF-α, and interferon-γ. Hence, kefir might be a significant inhibitor of the 'cytokine storm' that contributes to COVID-19. Here, we review several studies with a particular emphasis on the effect of kefir consumption and their microbial composition against viral infection, as well as discussing the further development of kefir as a protective supplementary dietary against SARS-CoV-2 infection via modulating the immune response. [ABSTRACT FROM AUTHOR]