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Dear Editor,
The Food Nutrition Board (FNB) of the Institute of Medicine of the National Academies recently published definitions for "dietary," "functional," and "total" fiber (7) as
- Dietary fiber consists of non-digestible carbohydrates and lignin that are intrinsic and intact in plants.
- Functional fiber consists of isolated, non-digestible carbohydrates which have beneficial physiological effects in humans.
- Total fiber is the sum of dietary fiber and functional fiber.
The American Association of Cereal Chemists (AACC) as a scientific organization with a long record of being deeply involved with various aspects of research on dietary fiber, including health benefits, analytical methodology, and the development, production, and promotion of foods containing fiber, must respond to this proposed definition. A complete discussion of this topic will be published in the May-June 2003 issue of CEREAL FOODS WORLD (5).
Irrelevant versus Relevant Definitions - A definition for dietary fiber must be scientifically sound, promote international harmonization, and define the constitution and makeup of a macrocomponent of food based on its physiological or physical-chemical properties, not its state of being. The FNB definition(s) do not satisfy these requirements. The FNB definitions do not reflect current scientific consensus on the physiology of dietary fiber and are operationally impractical. In contrast, AACC, utilizing a scientific review committee with representation from academia, industry, and government, accepting global input via teleconferences, and utilizing interactive workshops and website, adopted the following definition (1,2):
Dietary Fiber is the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fiber includes polysaccharides, oligosaccharides, lignin, and associated plants substances. Dietary fibers promote beneficial physiological effects including laxation, and/or blood cholesterol attenuation, and/or blood glucose attenuation.
The last sentence includes beneficial physiological functions for which there is significant scientific agreement, enabling enfranchisement of food components that offer these effects, but does not limit the physiological functions to those listed for perpetuity.
Analytical Concerns - The FNB definition incorporates references to "intrinsic and intact," terms that are not nutrition definitions or descriptions, merely terms reflecting a state of being. Intrinsic and intact are not physiologically relevant properties nor measurable quantities. Accurate measurement and characterization of "dietary" fiber...