Dietary fiber is a kind of sugar that is not easily digested by human body, and mainly comes from plant cell walls. According to chemical composition and structural characteristics, dietary fiber can be divided into soluble dietary fiber and insoluble dietary fiber. Insoluble dietary fiber, including cellulose, hemicellulose and lignin, cannot be digested in small intestine and fermented in colon. The chemical structure of dietary fiber contains carbon, hydrogen, oxygen and other elements, belonging to the category of carbohydrates, so it can be classified as organic matter. Organic matter refers to compounds containing carbon, and inorganic matter refers to compounds containing no carbon. The organic nature of dietary fiber makes it play a variety of important physiological functions in human body, such as promoting intestinal peristalsis, increasing satiety, regulating blood sugar and blood lipids.