Dietary Fibers: Structural Aspects and Nutritional Implications

Along with the brief outline of the definition evolution of dietary fibers, this chapter focuses on how the physical and chemical structures of fibers are related to the health effects. The role of fiber in the human digestive tract including oral, gastric, small intestinal, and large intestinal phases is also discussed. Our further emphasis is on the colonic microbial fermentation performance and health implications of dietary fibers. Fibers with higher water holding capacity or viscosity are desirable for slowing down the metabolic response (e.g., post prandial blood glucose level), whereas the fibers with slow fermentation throughout the colon and higher level of butyrate/propionate production are considered ideal for colonic health. Thus foods that have the balance of viscous and slowly fermentable fibers are considered beneficial in terms of overall nutrition and health. Although role of fibers in small intestine is well studied and known, how the fiber specificity can modulate the gut microbial ecology for desired health benefits still needs further research investigation.