Up to date knowledge on dietary fibre and its effects upon the human organism is summarized. There are great inconsistencies and differences of opinions, terminology and concepts used in this area, therefore a definition and classification of dietary fibre are given. The dietary fibre classification in terms of its chemical structure is shown in a diagram. Classification in to soluble and insoluble dietary (SDF and IDF) fibre and description of both types of fibre and their function on the digestive system is an integral part of this paper. Individual types of dietary fibre, their presence and contents in food, their breakdown and action in the digestive system are characterized. Final products of anaerobic fermentation of dietary fibre in the colon are described in the part on the importance of fibre. The final products are short chain fatty acid (SCFA) – acetic, propionic and butyric, further hydrogen, methane and carbon dioxide. The effects of these metabolites on the intestinal mucosa and liver 3-hydroxy-3-methylglytaryl-CoA-reductase are also described. The results of the study dealing with the influence of different types of dietary fibre types (SDF or IDF) on metabolic and nutritional disorders, or using a fibre in prevention of cardiovascular diseases (a ten-year Cardia study) form an important part. The negative influence of fibre is also mentioned, both excessive consumption (e.g. of bran) in people vegans and macrobiotics or patients with a stoma. The positive effect depends on the ratio of soluble and insoluble dietary fibre in a given food. The nutritional quality of fibre can be evaluated by assessment of final products of anaerobic fermentation after administration of fibre, e.g. the methane concentration in expired air.

        Key words: dietary fibre, definition and classification of fibre, soluble and insoluble fibre, short-chain fatty acids, methane.