II
Human Carbohydrate Digestive Enzyme System
Why Those suffering from Malnutrition and Those Two Years old and
Younger Will Benefit From Pre-digestion of Their Dietary Polysaccharides.
Sugar is the primary component of polysaccharides. Sugar is the
body’s primary source for energy. Glucose is the base sugar that is utilized
by the body for energy production. Other sugars, mainly fructose (from
sucrose in fruits) and galactose (from lactose in dairy products), are
converted by the body to glucose before energy is generated.
Energy is stored in sugar by plants through a process called
photosynthesis. This process takes carbon dioxide and water from the
environment, adds energy from sun light and forms sugar (6-CO2 + 6-H20 +
Energy = C6-H12-06 + 6-O2).
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pictures of glucose[9]
Animals obtain carbohydrates by eating foods that contain them. The
animal digests them (breaks them down into base sugars), and absorbs them.
Body cells and tissues then either convert the sugar molecules into the
storage polysaccharide called glycogen or metabolize the sugar molecules
into H20, CO2, and energy, the opposite process of photosynthesis.
All polysaccharides are made up of chains of sugar molecules linked
together. There are two main types of storage polysaccharides,
carbohydrates in plants and glycogen in animals. These are chains of
glucose. Carbohydrate consists of amylose, straight chains. and amylopectin,
made up of chains with branches. Glycogen, which is primarily stored in
muscle and liver, is more highly branched than amylopectin. These are held
together by alpha bonds, 1-4 bonds in straight chains and 1-6 bonds at
branches. These bonds can be broken down by human enzymes called
amylase (Lactase is an enzyme that breaks down lactose which contains a
beta bond) and debranching enzyme.
Cellulose is a noncarbohydrate polysaccharide which has glucose
linked in straight chains by beta bonds which can not be digested by
humans. Ruminants such as cows and insects such as termites digest
cellulose by harboring bacteria in their digestive systems that produce
enzymes that are capable of digesting cellulose. Cellulose acts as a fiber for
human consumption.
The major enzymes involved in carbohydrate, glycogen and
disaccharide digestion are alpha amylase, beta amylase, debranching
enzyme, maltase, and lactase. Beta amylase is found in seeds. Alpha amylase
is produced by the seeds of germinating plants. In animals, digestive alpha
amylase and debranching enzyme are produced by salivary glands and the
pancreas.
Alpha amylase attacks the end of the carbohydrate chains, breaking
the carbohydrate down at the 1-4 bonds to the disaccharide maltose.
Amylose can be broken down in this fashion. Alpha amylase will create
maltose up to a branch. It can not cleave the branch 1-6 bonds, leaving
residual polysaccharides and oligosaccharides or limit dextrins (compounds
made of up to ten monosaccharides). Alpha amylase can skip past the 1-6
bonds and continue cleaving the 1-4 bonds which the plant beta amylase can
not do. Debranching enzyme cleaves the 1-6 bonds, allowing beta amylase
to proceed with its digestive activities.
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Maltase (and lactase) is an enzyme manufactured in the brush border
cells of the duodenum and jejunum. This enzyme completes the digestive
process by breaking down maltose not digested by alpha amylase into two
glucose molecules and sucrose into a glucose and a fructose molecule
(lactose, which is not broken down by maltase, is similarly broken down into
glucose and galactose by lactase). These sugar molecules are absorbed into
the blood stream.
Salivary amylase and debranching enzyme begin the digestion of
ingested carbohydrate. This process is limited. First, there is no maltase.
Second, once the meal is swallowed and it reaches the stomach, the
enzymes, which are proteins, are denatured by the acid content of the
stomach and are partially digested by pepsin. This occurs even in neonates
and infants. Completion of carbohydrate and glycogen digestion occurs in
the small intestine by alpha amylase and debranching amylase produced by
the pancreas and maltase produced by the brush border cells of the
duodenum and jejunum.
There is a significant deficiency of amylase production in neonates,
infants, and toddlers. Amylase, in small amounts, can be found in the saliva
of neonates.[1] Neonatal serum amylase levels are very low.[3] The
duodenal fluid of newborns contains no amylase.[2] Serum pancreatic
amylase levels are very low in infants younger than 6 months old. These
levels then increase with age. Serum salivary amylase levels reach normal
adult levels by age 5 years old. Pancreatic amylase appears in the serum at a
later age. Below 3 months there are no pancreatic amylases in the serum.
These levels slowly increase over time reaching normal adult levels between
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the ages of 10 and 15 years old.[4] There is some amylase in duodenal fluid
at approximately 2 years old.[2]
Maltase activity reaches the lower range of normal adult activity by
28 to 32 weeks of gestation. Therefore, both healthy premature and full-term
infants should have adequate maltase activity.[10]
Amylase production has been shown to be reduced during marginal
and severe malnutrition in children.[7] Decreased pancreatic enzyme
production has frequently been recorded in protein energy malnutrition
because the pancreas requires optimal nutrition for enzyme synthesis. The
pancreatic head size, by ultrasound, is significantly smaller in malnutrition at
the same time that amylase levels are also lower. With nutritional
rehabilitation, the pancreatic head size and amylase levels concomitantly
return to normal.[8] Maltase activity is present but reduced secondary to
villous atrophy.[12]
The above discussion documents that the pre-digestion of starch-based
food by use of alpha amylase found in barley malt will aid in improvement
of the nutritional status of those less than two years old and those suffering
from malnutrition by producing maltose.
The presence of maltase in neonates and infants results in glucose
production and absorption by the gastrointestinal tract. This activity is
reduced but present during episodes of malnutrition. In addition, maltase is
present in barley malt, which compensates for the small bowel changes that
result in decreased maltase production by the reduced number of brush
border cells.
The limited dextrins are not predigested because debranching enzyme
is not present in barley malt. Debranching enzyme is rapidly denatured at 65
degrees centigrade, and kilning reaches 70 degrees centigrade. Thus, while
glucose is ultimately made available, complete pre-digestion of carbohydrate
to maltose does not occur utilizing barley malt flour.[11]
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BIBLIOGRAPHY
1 – The Contribution of Salivary Amylase to Glucose Polymer Hydrolysis in
Premature Infants – Murray R.D., Kezner B., Sloan H.R., McClung H.J.,
Gilbert M., Ailabouni A – Pediatric Resident, Feb 1986 Vol. 20 No 2, pp.
186-91
2 – Development of Functional Response in Humane Exocrine Pancreas –
Emanual Lebenthal MD, and P. C. Lee PhD – Pediatrics October 1980 Vol.
66 No. 4 , pp. 556 – 560
3 – Serum Levels of Immunoreactive Trypsin During Development:
Comparison with Levels of Lipase and Amylase – Colombo C., Maiavacca
R., Ronchi M., Bottani P., Stripparo L., Corbetta C., and Sereni L.P. –
Pediatric Gastroenterological Nutrition August 1989 Vol. 9 No 2, pp. 194-9
4 – Sources of Serum isoamylases and Their Normal Range of Variation
with age – Skude G. – Scandinavian Journal of Gastroenterology 1975 Vol.
10 No 6, pp. 577-84
5 – Maltase – Accessed at http://medicaldictionary.thefreedictionary.com/maltase on 11/9/08
6 – Why delay Solids? – Accessed at
http://www.kellymom.com/nutrition/solids/delay-solids.html on 11/10/08
7 – Pancreatic and Salivary Amylase Activity in undernourished Columbian
Children – Watson R.R., Tye J.G., McMurray, and Reyes M.A. – American
Journal of Nutrition April 1977 Vol. 30 No. 4, pp. 599-604
8 – Pancreatic size I Protein Energy Malnutrition: a predictor of Nutritional
Recovery – El-Hodhod M.A., Nassar M.F., Hetta O.A., and Gomaa S.M. –
European Journal of Nutrition April 2005 Vol. 59 No. 4, pp. 467-73
9 – Glucose, What is Glucose About its science, Chemistry and Structure –
Accessed at www.3dchem.com/molecules.asp?ID=423 on 11/10/08
10 – Allergy Advisor, A case Study – Accessed at
http://allergyadvisor.com/Educational/June07.htm on 11/10/08
11 – The Theory of Mashing – Accessed at
www.homebrewtalk.com/wiki/index.php/Enzymes on 11/10/08
12 – Contribution of Villous Atrophy to Reduced Intestinal Maltase in
Infants With Malnutrition – Nichols B.L., Nichols V.N., Putman M., Avery
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S.E., Fraley J.K., Quaroni A., Shiner M., Sterchi E.E., and Carrazza F.R. –
Journal of Pediatric Gastroenterology and Nutrition 2000 Vol. 30 No. 5, pp
494-502
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