Fermented Foods Strengthen Immunity against Viral Infections

Fermented foods have been shown to exert positive effects on gut health and immune function. However, the potential of fermented foods to enhance the bioavailability of bioactive compounds and support the growth of the beneficial microbial community’s key factors in antiviral immunity remains less explored. In this review, we show that probiotic-fermented food improves the bioactive compound contents and is increasingly studied by basic and clinical researchers. Bioactive compounds, including phenolic, alkaloids, terpenoids, flavonoids, stilbenes, coumarins, tannins, anthocyanidins, flavones, isoflavonoids, and polyphenols, are increased in the probiotic fermentation conditions. Additionally, beneficial bacteria such as Lactobacilli, Bifidobacteria, Pediococcus, and Weissella are also restored in the fermented foods. These bioactive compounds, combined with a functional microbiota, play a role in preventing viral infections by targeting influenza, noroviruses (NoVs), Murine norovirus-1 (MNV-1), and COVID-19, while also stimulating the immune function of the host. It was suggested that clinical and pre-clinical investigations are required to explore the dose-response and duration efficacy of probiotic fermented foods against viral infections.