What is Dietary Fiber?

Nuts and sultanas: a source of fiber
Nuts and sultanas: a source of fiber

Dietary fiber (fibre) is a food substance derived from plants which is resistant to digestive enzymes in the human digestive system. The term `fiber’ covers a number of different substances of differing chemical structures.

There are many classifications of fiber which are based on the properties of these various substances. The classification below depends on whether a fiber is soluble or not, whether it undergoes fermentation or on its viscosity and chemical structure. 1


Soluble fiber

Insoluble fiber

The fiber content of the average diet is approximately 67%-75% insoluble and 25%-33% soluble fiber.1


Fermentable fiber

Non-fermentable fiber


Viscous or `sticky’ fiber

Non viscous fiber:

Chemical structure



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  1. 1. Kozłowska L. (2010) Rola błonnika pokarmowego w utrzymaniu prawidłowej pracy jelit, Żywność dla zdrowia 13(8):23-27.