ABSTRACT
There is new evidence that the macrostructure of plant foods participates in the physiological effects of dietary fiber and this needs to be incorporated in a revised definition of dietary fiber. The first definition implied that dietary fiber is derived primarily from edible plant cell walls. The cell wall material of edible plant tissues in the diet constitutes the botanical structure of the plant foods and it is rich in micronutrients. The subsequent definitions have been either based on plant cell walls and/or on resistance to digestion, and the reference to the edible plant tissues as the origin of dietary fiber was not always mentioned. It has been shown for various edible plant tissues that the loss of structural integrity of the cell walls is associated with a significant reduction of physiological effects (regularizing colonic function, lowering peak blood glucose and insulin levels, and reducing the rate and extent of fat absorption). Relying on dietary fiber analyses alone to determine the presence of dietary fiber is problematic because (a) they cannot measure the degree of retention of the structural integrity of the cell walls and (b) these methods cannot distinguish between dietary fiber and materials such as ruminant fiber, non-edible tissues and non-food material. Therefore, to be considered dietary fiber, a food material should meet the three following conditions: 1) originates from “the cell walls of edible plant tissues in the traditional human diet,” 2) retains an intact botanical structure, and 3) is measurable by current dietary fiber methods.
