Chemistry Reference
In-Depth Information
fiber is nonstarch polysaccharides (~8 to 18 g/day). The third group of fiber is oligo-
saccharides (onions, artichoke, banana, cecoria), which although important to health,
are today regrettably consumed in much too small quantities (~2 to 8 g/day).
22
8.4 DIETAry FIbErs—FuNCTIoN AND DEFINITIoN
Dietary fiber is the collective name for pure fibers obtained from processing
various plants. The term dietary fiber was coined some 50 years ago, and was then
suggested to consist of cellulose, hemicellulose, and lignin,
23
all indigestible con-
stituents of the cellular walls of plants. Some 20 years later, the concept was defined
as “plant fibers and lignin, which are resistant to hydrolysis by the digestive enzymes
of ma n.”
24
A more recent definition by the American Association of Cereal Chemists
(AACC) suggests that dietary fiber is “the edible parts of plants or analogous carbo-
hydrates that are resistant to digestion and absorption in the human small intestine
with complete or partial fermentation in the large intestine. Dietary fibers include
polysaccharides, oligosaccharides, lignin, and associated plant substances. Dietary
fibers promote beneficial physiological effects including laxation, and/or blood cho-
lesterol attenuation, and/or blood glucose attenuation.”
25
According to this definition,
some noncarbohydrates like waxes, phytate cutin, saponins, suberin, and tannins,
also are included in the concept, substances sometimes referred to as associated
with nonstarch polysaccharide and lignin complex in plants. Of the many substances
known, only a few have been properly investigated as dietary fibers and for health
purposes, for example, as medical fibers.
Supplemented fibers are associated with several health benefits. The best docu-
mented physiological effects, in addition to providing energy and nutrients to the
host and flora, are that they:
•
Change in mucosal structure, increase mucosal growth, and improve mucosal
function.
Increase in intestinal flora, relieve constipation, reduce production of putrifactive
•
gases, and provide resistance to invading microorganisms
Reduce serum triglycerides, serum cholesterol, and very low density (VLD)
•
lipoproteins
Reduce the glycemic response to eating.
•
•
Improve water and electrolyte balance and increase bioavailability and absorption
of minerals, such as calcium, magnesium, iron, and zinc.
Consumption of medical fibers should always be regarded as a surrogate for not
consuming enough fresh fruits and vegetables. There is no solid information to sup-
port that supplementation of medical fibers to healthy individuals eating a diet rich in
fruits and vegetables is associated with additional health benefits. Medical fibers are
mainly needed because the individual has lost the ability to consume enough fresh
fruits and vegetables. This is often the situation in persons with severe allergies, in
old and debilitated persons, and in persons with some gastrointestinal (GI) disorders,
