Figure 2. General scenario for generation and effects of small metabolites created as a result of the digestion of glycosylated lactoferrin and/or other whey milk glycoproteins by different microorganisms from the intestinal microbiota, on the COVID-19 severity, aging, and their interconnection.

Metabolites can be engaged in the direct interactions with the SARS-CoV-2 particles and/or show indirect potential against the viral replication through modulation of the immune response network via the antigen presenting cells (Dendritic cell and Toll-Like receptor 2, 4, and 8). These effects dependent on the kind of food stud and gut microbiota balance, and subsequently on their concentrations and distributions that change with the age. SCFAs (short-chain fatty acids), OSs (oligosaccharides), HMOs (human milk oligosaccharides).