Evaluation of the relative available energy of several dietary fiber.pdf

246 J Nutr Sci Vitaminol, 60, 246–254, 2014 Dietary fiber (i.e., largely indigestible carbohydrates) has beneficial effects for health and is actively used in health foods and functional foods (1, 2). Dietary fiber taken orally reaches the large intestine without being digested by a-amylase or disaccharidases present in the mucosa of the small intestine. In the large intestine, dietary fiber is fermented to varying degrees by intes- tinal microbes and metabolized into short chain fatty acids, carbon dioxide, hydrogen, methane, and bacterial cell components (3–6). Among them, short-chain fatty acids are absorbed from the large intestine and used solely as the energy source of the host. That is, even carbohydrates that are not digested and not absorbed provide available energy to a living body by being fer- mented and absorbed in the large intestine (5). Energy values for fermentable fibers are an important matter for regulatory bodies as they are incorporated into on-pack labels, and for weight control products, as a help to direct consumer choice (2). The available energy of nondigestible carbohydrate in humans is eval- uated using balance studies and other methods (7, 8). However, this is not practical, because balance studies are time-consuming, expensive, and very stressful for subjects. Although an indirect and simple method to evaluate the available energy of nondigestible carbohy- drates is desirable, it has not been established yet. The amount of available energy of nondigestible and fermentable carbohydrates is dependent upon the amount of short-chain fatty acids produced in the fer- mentation by intestinal microbes. Thus, energy produc- tion is dependent on the fermentability of nondigestible carbohydrates which reach the colon. We estimated the relative available energy value (RAE) of dietary fiber materials (DFMs) based on the breath hydrogen excre- tion (BHE) and calculated the relative ratio versus the amount of hydro