Dietary fibre is the name given to a complex group of substances found only in plants. They are celluloses, hemicelluloses, pectic substances and lignin. Because the first three of these are carbohydrates, dietary fibre is sometimes called unavailable carbohydrate or non-starch polysaccharide. Dietary fibre from one species of plant may be unlike the fibre derived from a different species of plant and this variation may produce very different effects.
Dietary fibre cannot be digested in the normal way by humans, but some is broken down and used by the micro-organisms in the colon. These micro-organisms plus any intact fibre form the bulk of the faeces. Estimates of the amounts of dietary fibre in foods depend on the methods used for fibre analysis and hence the fibre contents of foods given in different reference tables may be very dissimilar. For example, older reference tables usually give the fibre content of wholemeal bread as about 3 g/100 g, whereas
the current value is given as about 8–9 g/100 g. Most values for fibre should be considered guides rather than accurate numbers.
Dietary fibre, Dietary fibre intake, Effects of dietary fibre, Bulking effect, Colonic gas (flatus), Effect on blood cholesterol, Diverticular disease of the colon, Irritable bowel syndrome, Irritable bowel syndrome, Weight control, Effect on bowel cancer, Designing a high-fibre diet