Fig. 2. Under homeostasis between gut microbiota and the host, intestinal bacteria can metabolize drugs, promote browning of white fat, and convert dietary or compound water compounds into nutrients for host utilization. The gut microbiota and the host's liver and brain form the gut–liver axis and gut–brain axis, respectively, which participate in the life metabolic activities of various organs. Once the intestinal microflora become imbalanced, liver diseases, gastrointestinal diseases, and nervous system diseases will be induced. Specific diseases are shown in the figure.
