The liver is the central station of the body’s metabolism. After food is digested, it enters the liver through the portal vein in the intestine, and the liver is required to participate in the metabolism of almost all of the nutrients involved. Without the liver, life cannot be sustained. The liver plays an important role in the storage, distribution and regulation of sugar. After food is broken down into glucose, part of it enters the blood circulation for the body to use, while most of it is synthesized into hepatic glycogen by liver cells and stored in the liver. When hunger, labor or fever, liver cells can break down liver glycogen into glucose for human use. When the body’s nutritional status is good and liver glycogen is abundant, it can protect the liver from damage. The liver synthesizes more than 40% of the total protein synthesized by the whole body. The main one is albumin, but also fibrinogen and prothrombin. When liver damage is severe, plasma albumin drops and swelling and ascites can occur. Fibrinogen and prothrombinogen are reduced, which can cause bleeding. The liver can process the indirect bilirubin produced by the destruction of senescent red blood cells into direct bilirubin, which is then excreted from the bile duct to the intestine to aid in the digestion of fats. When the liver is damaged, the function of processing indirect bilirubin and excreting direct bilirubin decreases, and the concentration of the two types of bilirubin (called total bilirubin) in the blood rises, and jaundice occurs. The digestion, absorption and utilization of fats are closely related to the liver. Under normal conditions, the various components of blood lipids in the body are relatively constant and depend on the liver to regulate them. Liver lesions can also be caused when fat metabolism is disturbed, such as fatty liver. Cholesterol decreases significantly in severe liver disease. The liver is the site of storage and metabolism of many vitamins such as vitamins A, B, C, D, E, K and folic acid. The liver is involved in the process of hormone metabolism. In normal times, the body’s hormone levels are kept in balance and excess hormones are destroyed by the liver. If the liver is diseased, such as chronic hepatitis and cirrhosis, the amount of estrogen in the body increases due to the disruption of estrogen destruction and inactivation, causing gynecomastia, menstrual irregularities in women, capillary dilation, such as spider moles, and edema and oliguria due to the disruption of antidiuretic hormone inactivation of aldosterone. The liver detoxifies harmful substances and foreign poisons and toxins, including drugs, produced during the metabolic process through redox and binding. There is also a phagocyte in the liver that has the function of engulfing bacterial foreign bodies. The liver protects the health of the body through detoxification and phagocytosis.