Table 1.

Main functions of the gut microbiota.

Function
Protective	Countering the colonization and translocation of pathogenic and pathobiont microorganisms by the production of antimicrobial substances and competition for nutrient and receptor sites Synthesis of enzymes capable of transforming and neutralizing xenobiotic substances (e.g., drugs and, in particular, antibiotics, environmental contaminants, compounds widely used in agriculture, and zootechnics) Activation of innate and adaptive immunity Production of anti-inflammatory cytokines
Trophic Metabolic Structural	Food compound degradation Production of group B vitamins, vitamin K, biotin, and folic acid Amino acid biosynthesis Biotransformation of bile acids Regulation of fat deposits Absorption of water and minerals (iron, magnesium, calcium) Angiogenesis promotion Production of compounds with trophic function for the enterocyte (e.g., short-chain fatty acids, aminoacids, polyamines, and growth factors) Epithelial cell differentiation and growth Energy recovery Fermentation of non-digestible substrates and mucus Development of intestinal crypts and villi Reinforcement of mucosal barrier function Modulation of bone mass density Optimization of neurocognitive performance Mood modulation