Food fiber is the tough wall layer of plant cells, plant food is difficult to be digested by the human body, water-soluble and insoluble two kinds of substances, its composition includes cellulose, hemicellulose, lignin, pectin, alginate, agar and other complex sugars, etc., all belong to polysaccharides; these substances constitute the cereal skin, wheat bran and vegetables, fruits, roots, skins, stems, leaves, etc.; they are not absorbed, and do not provide calories. Although the nutritional value of food fiber is low, it has a great effect on the body’s metabolism. Food fiber has a variety of beneficial functions for the human body, modern medicine is called the body cleaner.