The so-called crude fiber is what we usually call dietary fiber. It is a type of non-starch polysaccharide among carbohydrates, mainly derived from plant cell walls. Dietary fiber is difficult to be digested and absorbed by the human body, and most of it tastes rough. It was called crude fiber in early nutrition.

Foods containing dietary fiber mainly include grains, vegetables, fruits, beans, etc. Among them, it is divided into soluble dietary fiber and insoluble dietary fiber. The former are pectins, gums and viscose, which are soluble in water and are mainly found in fruits, oats, barley and some beans. Most dietary fibers are insoluble, such as cellulose and hemicellulose. Most crude fiber foods on the market are added with coarse grains and miscellaneous grains containing this type of insoluble dietary fiber, such as corn, wheat bran, rice bran, etc.