Antiviral Mechanisms Related to Lactic Acid Bacteria and Fermented Food Products

The Covid-19 pandemics laid stress on the significance of having a strong immune system in coping with viral infections. Nutrition is important in the modulation of our immune systems. Recent studies have shown that probiotics, most of which are lactic acid bacteria (LAB) naturally present in fermented food products, can boost the immune system of their host. Although responses are generally strain and dose dependent, in one way or another, most LAB are capable of enhancing both the innate and the adaptive immune responses in animal model systems. In addition to their ability of boosting the immune system, LAB directly or indirectly by means of the fermentation process, can generate bioactive metabolites having antiviral properties, such as peptides. LAB are shown to have antiviral mechanisms that affect both upper respiratory tract and gastrointestinal viral infections. Not only live cells but also heat-killed cells of probiotics (paraprobiotics) are shown to be effective. These wide range of antiviral mechanisms suggest that the diversity of LAB in the food product is likely to enhance the variety and strength of health benefits obtained from fermented foods. Traditional fermented foods have significantly higher microbiodiversity with respect to the LAB species, as compared to those produced by commercial cultures. This is particularly valid for the Lactobacilli, where several species and strains have proven to be antiviral probiotics and are natural inhabitants of fermented foods at the same time. While drawing attention to the antiviral properties of both live and dead cells of LAB, this review aims to underline the significance of supporting our health with the wealth of foods that are rich in terms of their microbial diversity. Further scientific research must focus on the several technical, biological, and clinical aspects of traditional fermentations.