There is no official definition of dietary fiber. Various nations have adopted various definitions for the purposes of food labeling and research. In general terms, dietary fiber has been considered to be the components of foods that are non-digestible in the human small intestine. This traditional understanding of fiber assumed that it came exclusively from plants. Some nutrition scientists prefer that dietary fiber remain associated with or obtained solely from the edible parts of plants.
Dietary fiber includes polysaccharides, oligosaccharides, lignin and associated plant substances.
Such a definition would be quite different than current definitions for food ingredients and nutrients. No endorsement of products or firms is intended, nor is criticism implied of those not included.