Equipping People To Make Sense Of What They Are Told
Carbohydrates are the most abundant organic compounds found in nature. Carbohydrates
(Carbon + Water) are produced by green plants and by bacteria using the process
known as photosynthesis - Latin words for light and putting together, in which carbon
dioxide is taken from the air by means of solar energy to yield the carbohydrates
as well as all the other chemicals needed by the organisms to survive and grow.
The carbohydrate group consists principally of sugar, starch, dextrin, cellulose,
and glycogen, substances that constitute an important part of the human diet and
that of many animals.
There are three types of carbohydrates:
Simple carbohydrates.
Complex carbohydrates.
Dietary Fibre.
All three types are composed of units of sugar:
Simple carbohydrates - have one or two units of sugar. One unit is known as a simple
sugar or a monosaccharide - mono (one) - saccharide (sugar).Two units is known as
a double sugar or a disaccaride - di (two) - saccharide (sugar).
Complex carbohydrates - have more than two units of sugar linked together. These
are also known as polysaccharides - poly (many) - saccharides (sugars).
Dietary Fibre - sometimes known as roughage - is unlike other carbohydrates. Dietary
fibre consists of non-digestible carbohydrates and lignin that are intrinsic and
intact in plants. This includes plant non-starch polysaccharides - e.g. cellulose,
pectin, gums, hemicellulose, and fibres contained in oat and wheat bran, oligosaccharides,
lignin, and some resistant starch.
Digestive enzymes are unable to break the bonds that hold the sugar units in dietary
fibre together, however bacteria in the intestines is capable of converting a small
amount of dietary fibre to fatty acids.
The body runs on glucose as its main energy source which is provided by digestible
carbohydrates from foodstuffs. As carbohydrates are broken down by the body and absorbed
into the blood stream as glucose (blood sugar) the level of Insulin rises. Insulin
encourages receptors in the muscle cells to open up and allow the glucose to enter.
Once glucose enters the muscle cell it is either metabolised to supply energy or
converted to glycogen by special enzymes and stored until it is required for energy
use.
Most carbohydrate intake should be in the form of complex carbohydrates. Complex
carbohydrates, with few exceptions, break down slowly supplying a steady source of
energy this lessens the spikes in insulin use.
Energy comes from muscle glycogen (stored carbohydrates) and glucose, circulating
in the blood stream.
Proper digestion requires coordinated movements of the stomach and intestines to
mix food with digestive enzymes, to stir the nutrients so they approach the intestinal
wall for absorption into the body, and to propel the intestinal contents through
the digestive tract. This movement of the walls of the gastrointestinal (GI) tract
and their contents is known as gastrointestinal motility.
There is considerable normal variability among healthy those in transit times through
different sections of the gatrointestinal tract.
The time required for material to move through the digestive tube is significantly
affected by the composition of the meal.
Transit time is influenced by such factors as psychological stress and even gender
and reproductive status.
The time taken for food or other ingested objects to transit through the gastrointestinal
tract varies depending on many factors, but roughly, it takes 2.5 to 3 hours after
meal for 50% of stomach contents to empty into the intestines. Total emptying of
the stomach takes 4 to 5 hours. Subsequently, 50% emptying of the small intestine
takes 2.5 to 3 hours. Finally, transit through the colon takes 30 to 40 hours.
Colorado State University > Gastrointestinal Transit: How Long Does It Take? Last
updated on May 27, 2006. Author: R. Bowen Camilleri M, Colemont LJ, Phillips SF,
etc. Human gastric emptying and colonic filling of solids characterised by a new
method. Am J Physiol Gastrointest Liver Physiol. 257:284, 1989.
Charles F, Camilleri M, Phillips SF, etc. Scintigraphy of the whole gut: clinical
evaluation of transit disorders. Mayo Clin Proc 70:113, 1995.
Degen LP and Phillips SF. Variability of gastrointestinal transit in healthy women
and men. Gut 39:299, 1996.
Iwanaga Y, Wen J, Thollander MS, etc. Scintigraphic measurement of regional gastrointestinal
transit in the dog. Am J Physiol Gastrointest Liver Physiol 275:904, 1998.
Metcalf AM, Phillips SF, Zinsmeister AR, etc. Simplified assessment of segmental
colonic transit. Gastroenterology 92:40, 1987.
Proano M, Camilleri M, Phillips SF, etc. Transit of solids through the human colon:
regional quantification in the unprepared bowel. Am J Physiol Gastrointest Liver
Physiol 258:856, 1990.
Marlett JA, McBurney MI, Slavin JL. Position of the American Dietetic Association:
Health Implications of Dietary fibre. J Am Diet Assoc. 2002; 102(7): 993-1000.
Howarth NC, Huang TT, Roberts SB, McCrory MA. Dietary fibre and Fat Are Associated
with Excess Weight in Young and Middle-Aged US Adults. J Am Diet Assoc. 2005;105(9):1365-72.
Seki T, Nagase R, Torimitsu M, et al. Insoluble fibre is a major constituent responsible
for lowering the post-prandial blood glucose concentration in the pre-germinated
brown rice. Biol PharmBull. 2005 Aug;28(8):1539-41.
1.Asp NG. Resistant starch. Proceedings from the second plenary meeting of EURESTA:
European FLAIR Concerted Action No. 11 on physiological implications of the consumption
of resistant starch in man. European Journal of Clinical Nutrition 1992;46 (Suppl
2):S1
