The term dietary fibre is generally understood to mean complex, long-chain (high-molecular) carbohydrates, as well as some other organic compounds that, in the main, cannot be digested by human gastrointestinal tract enzymes. Depending on their structure, they can be partly broken down in the large intestine by anaerobic intestinal bacteria. Cellulose and pectins rank amongst the most well known dietary fibres.

They are used in plants for building up their supporting structures. They are likewise used in food production for building structures. E.g. pectin is used as a gelling agent in jam.

Dietary fibres possess several properties, which have positive effects on our digestion. Their high water binding capacity, for example, helps increase stool mass. In doing so they speed up intestinal passage. The concentration and retention time of carcinogenic and cancer-promoting compounds in the intestinal lumen are therefore reduced.

They have a partial prebiotic effect, i.e. they promote the growth of bacteria trunks, such as bifidobacteria, that are positive to our intestinal flora. Epidemiological studies show that the plentiful consumption of food that is high in dietary fibre reduces occurrences of cardiovascular illnesses, cancer of the colon, diabetes mellitus type II, hypertriglyceridemia (raised level of triglyceride in the blood), and hypercholesterolemia (high level of cholesterol in the blood).

Chocolate also contains dietary fibre: the darker the chocolate, the more dietary fibre it contains. They originate from the cocoa present or added ingredients, like nuts.