Agriculture Reference
In-Depth Information
glucose are enzymatically transformed into glucose for their subsequent processing
by the metabolic machinery of the hepatic cells.
Ingestion of carbohydrates in the human diet has received particular attention in
recent years due to the duality of their nutritional value. Carbohydrates constitute the
main energy source for adult humans and have particular nutritional importance in
children due to the high energy requirements during this developmental stage. The
child's central nervous system (CNS) has much higher energetic requirement than
the adult CNS. It is well known that the main energy source for the CNS is glucose;
therefore, some of the most common food supplements in infant formulas are based
on maltodextrins produced by partial chemical or enzymatic hydrolysis of starch
(Holliday 1971; Elia 1992; Chugani 1998; Peters et al. 2004). In addition, carbo-
hydrates are indispensable sources of energy for high-performance athletes; thus,
maltodextrins and fructose are also normal components of energetic or “reconstitut-
ing” beverages. Ingestion of nondigestible carbohydrates, generically called dietary
fiber, can cause qualitative changes in the intestinal flora, changes in intestinal motil-
ity, and changes in the chemical composition of feces. Some of the changes induced
by the dietary fiber can be beneficial for gastrointestinal function and constitute the
basis for the development of “prebiotic” and “probiotic” foods (Rolfe 2000; Freitas
et al. 2003). In contrast with the beneficial nutritional effects of carbohydrates, their
ingestion in large quantities has been associated with chronic and degenerative dis-
eases such as obesity, diabetes, coronary disease, and metabolic syndrome (Holliday
1971; McCall 2004; Peters et al. 2004).
Depending on their biochemical and physicochemical properties, carbohydrates
can therefore have diverse nutritional and physiologic effects. However, from the
point of view of nutritional intake, carbohydrates have been classified as glucogenic
and nonglucogenic, which describes their ability to produce absorbable free glucose
monomers generating a glycemic response, that is, an increment in the blood glucose
concentration (Azad and Lebenthal 1990; Wursch and Pi-Sunyer 1997). In general,
glucogenic carbohydrates can be degraded in the gastrointestinal tract into the easily
absorbable monosaccharides glucose, galactose, or fructose, which constitute most
of the caloric intake in human diets. In contrast, nonglucogenic carbohydrates such
as cellulose, inulin, and gum arabic cannot be degraded to monosaccharides due to
the absence of enzymatic mechanisms for their digestion in the human gastrointes-
tinal tract. Part of these nonglucogenic carbohydrates can be fermented by colonic
bacterial flora with production of short-chain fatty acids like butyrate, propionate,
and others but reduced energy production for the host. Nonglucogenic carbohydrates
that are not fermented are excreted in the feces, contributing to their moisture and
consistency (Anderson 1985; Correa-Matos et al. 2003; Englyst and Englyst 2005;
Livesey 2005).
h
i s t of r y
of f
m
a j o r
f
o o D
C
a r b o h y D r a t e s
The historic patterns of carbohydrate consumption by humans have experienced
important changes. Carbohydrate consumption by primitive human populations
most probably was limited, dependent on environmental or geographic conditions,
and influenced by their collection patterns. Gathering of fruits, leaves, seeds, and
