Carbohydrates are composed of carbon, hydrogen and oxygen, divided into monosaccharides, disaccharides and polysaccharides, which mainly exist to provide energy, save protein, maintain brain cell function, resist ketone bodies and other physiological functions. 1.Provide energy: carbohydrates in the body contain glycogen in muscles and liver, glycoproteins and glycolipids in the body. Absorption, provide energy for the body; 2, save protein: the body carbohydrate sufficient, then the body does not need to use protein to provide energy, so that protein is really used to synthesize new protein and the renewal of cellular tissue; 3, maintain brain cell function: carbohydrate glucose is the only source of energy to maintain the brain, involved in the composition of cells and tissues, maintain the normal function of brain cells; 4, Resist ketone bodies: carbohydrates in the body provide sufficient energy to prevent the conversion of fat into energy, reduce the accumulation of fat metabolites ketone bodies and prevent ketoacidosis; 5. Constitute cells and tissues: cells and tissues need carbohydrates to participate in the composition in the form of glycolipids, glycoproteins and proteoglycans; 6. Other: carbohydrates also have the effect of lifting toxins such as bilirubin and can improve intestinal function and prevent Constipation. But the consumption of carbohydrates can also produce obesity, blood sugar, heart disease and other risks, so in the choice of carbohydrate food should be moderate and avoid excessive consumption.