Physiological effects of dietary fiber (DF) are the result of complex interacting mechanisms between the components of food which is not digested by the endogenous enzymes of the digestive tract and the conditions of gastrointestinal environment, such as pH, ionic strength and other food components. Chemical nature and structure of each component of DF are two factor that determine their behaviour in lumen intestinal. This article report the main functional properties of DF and explain how these are responsible of physiological effects developed by DF in gastrointestinal tract.