Do the Physical Structure and Physicochemical Characteristics of Dietary Fibers Influence their Health Effects?

Fiber is an essential part of plant-based foods and plays an important role in human health. Fibers are characterized by both their intrinsic (chemical and physical structure) and their physicochemical (interactions with digestive environment) properties. Intrinsic properties are mainly molecular weight, degree of crystallinity, and particle size, whereas physicochemical properties are mainly solubility, porosity, and ability to adsorb bile acids and complex minerals and trace elements. These determine their viscosity, reduction of some nutrient bioavailability, and their fermentability. In general, soluble fibers are rapidly and fully fermented, whereas insoluble fibers are more slowly and only partially fermented. Hence the “slow versus rapid fiber” concept. However, very little is known about the physiological effects of different fermentation rates in humans. In addition, fibers are vectors for gradual delivery of bound phytochemicals (“fiber co-passengers”) along the digestive tract, notably antioxidants at colonic level. Globally, the impact of fiber fermentation on human health remains largely misunderstoo