Chemistry Reference
In-Depth Information
to remember that key nutrients, such as omega-3 fatty acids, glutamine, glutathione,
and several other nutrients, are heat-sensitive and do not tolerate processing or stor-
age to any great extent. Plant fibers that have been dried, heated, or microwaved
cannot be expected to contain any large amounts of these key nutrients; they mainly
come from unprocessed foods. It is highly desirable that, whenever possible, the
supply of commercial nutrition formulas is complemented by a supply of fresh fruit
and vegetable juices, produced as locally as possible. It is also desirable that several
fibers are supplied in parallel, and that both soluble and nonsoluble fibers are used.
For example, oat fibers are mainly metabolized in the proximal colon, whereas wheat
fibers are known to be effective in the distal part of the colon, for example, the part of
the colon where most cancers are localized. Oat has mainly shown sepsis-reducing
effects while wheat has mainly been effective in cancer prevention. Among the fibers
commonly used in clinical nutrition are discussed below.
8.6.1 Algal Fibers
Most of the algal fibers are resistant to hydrolysis by human endogenous digestive
enzymes, but are fermented by colonic flora to various degrees. The soluble fibers
consists in lamarans (a sort of β-glucan associated with mannitol residues), fucans
(sulfated polymers associated with xylose, galactose, and glucoronic acid), and alg-
inates (mannuronic and guluronic acid polymers). The insoluble algal polymers con-
sist mainly of cellulose. Fermentation of alginates yields high levels of acetate (80
percent), while lamarans preferably yield butyrate (16 percent). It is most likely that
algal fibers will be routinely used in clinical nutrition within a few years.
8.6.2 Fructans
Fructan starches and sucrose serve the plant as its energy reserve. These sub-
stances are also produced by bacteria and fungi. Fructans are said to enhance the
tolerance of the plant to stressful conditions and make it possible for the plants to
survive under harsh conditions, such as low temperature and draft. The most well
known fructans are inulin (rich in chicory, artichoke, onions, banana) and phleins
(rich in various grasses). Thus far, mainly inulin has been tried in human nutri-
tion. Various oligosaccharides are reported to stimulate the flora and especially the
growth of
Lactobacillus
and
Bifidobacterium
in the large intestine and to reduce the
content of potentially pathogenic microorganisms (PPMs) in the intestine. Increase
in the
Bifidobacterium
flora is regarded as especially favorable as bifidobacteria are
known to produce important vitamins, among them thiamine, folic acid, nicotinic
acid, pyridoxine, and vitamin B
12
, which is of great importance for health. A fructan
called neokestose, found in onion, is reported to have even better ability than inulin to
promote growth of lactic acid bacteria (LAB).
30
Supplementation of fructans is also
reported to reduce concentrations in serum of insulin, cholesterol, and triacylglyc-
erol. It is also reported to promote absorption of calcium and other minerals. Other
oligosaccharides, such as those extracted from peas and beans, especially soy bean
