CN

1. CLINICAL NUTRITION
MOHAMED SATHAK COLLEGE OF ARTS AND SCIENCE
SHOLINGANALLUR-CHENNAI.
COURSE INSTRUCTOR
Ms JESSICA SUBASHINI MOSES
Asst.Professor
Dept. of Home Science-CND

2. Digestion
The process of making food absorbable
by mechanically and enzymatically
breaking it down into simpler chemical
compounds in the digestive tract.

3. Absorption
Absorption is the process where the digested
food molecules are absorbed into the
bloodstream and then transported to various parts
of our body. Absorption is the process by which
the digestive contents are absorbed by the blood
and distributed to the rest of the body.

4. The inner wall of the small intestine has many tiny finger-like projections of the mucous membrane
called intestinal villi The villi are slightly more than 1 mm or about 4/100 inch in length and give the
inner wall a soft texture similar to vel-vet fabric. They are most numerous in the duodenum and proximal
jejunum, decreasing in size along the way from the duodenum to the ileum. The villi help to contract the
intestinal contents and increase the sur-face area of the intestinal lining to aid in absorption of digestive
products. In the duodenum, the villi appear like leaves.
Each villus has a layer of absorptive, simple columnar epithelium consisting
of enterocytes, a core of connective tissue with capillaries, a lymphatic capillary called
a lacteal, and nerve fibers. The cores have dense capillary beds. The lacteals are
actually wide lymphatic capillaries. Nutrients are carried away by blood capillaries and
lacteals. Extremely long and densely packed microvilli are found in the absorptive
mucosal cells. Therefore, the mucosal surface appears “fuzzy” and is referred to as
the brush border.

5. Metabolism refers to the chemical
(metabolic) processes that take place as
your body converts foods and drinks into
energy. It’s a complex process that
combines calories and oxygen to create
and release energy. This energy fuels
body functions.

7. CARBOHYDRATES
Metabolism, digestion and
absorption

8. From the Mouth to the Stomach
DIGESTION OF CARBOHYDRATES
The mechanical and chemical digestion
of carbohydrates begins in the mouth.
Chewing, also known as mastication,
crumbles the carbohydrate foods into
smaller and smaller pieces. The salivary
glands in the oral cavity secrete saliva
that coats the food particles. Saliva
contains the enzyme, salivary amylase.

9. When carbohydrates reach the stomach no
further chemical breakdown occurs because the
amylase enzyme does not function in the acidic
conditions of the stomach. But mechanical
breakdown is ongoing the strong peristaltic
contractions of the stomach mix the
carbohydrates into the more uniform mixture of
chyme.

10. From the Stomach to the Small Intestine
The chyme is gradually expelled into the upper part of the small
intestine. Upon entry of the chyme into the small intestine, the
pancreas releases pancreatic juice through a duct. This
pancreatic juice contains the enzyme, pancreatic amylase, which
starts again the breakdown of dextrins into shorter and shorter
carbohydrate chains. Additionally, enzymes are secreted by the
intestinal cells that line the villi. These enzymes, known
collectively as disaccharidase, are sucrase, maltase, and lactase.

11. Absorption: transportation to the blood stream
The cells in the small intestine have membranes that contain
many transport proteins in order to get the monosaccharides and
other nutrients into the blood where they can be distributed to
the rest of the body. The first organ to receive glucose, fructose,
and galactose is the liver. The liver takes them up and converts
galactose to glucose, breaks fructose into even smaller carbon-
containing units, and either stores glucose as glycogen or
exports it back to the blood.

12. Metabolism of carbohydrates:
Glycogenolysis and glycogenesis
 Glycogenolysis is the biochemical degradation of glycogen to glucose,
while glycogenesis is the opposite, the formation of glycogen from glucose.
 Glycogenolysis takes place in muscle and liver tissue cells in response to
hormonal and neuronal signals.
 In particular, glycogenolysis plays an important role in the fight or flight
response induced by adrenaline and the regulation of blood glucose levels.
 The reverse process, glycogenesis, the formation of glycogen from glucose,
occurs in the liver and muscle cells when glucose and ATP are present in
relatively high amounts.
 In glycogen synthesis, an ATP is required for each glucose unit incorporated
into the branched polymer structure of glycogen.
 Glucose (in the form of glucose-6-phosphate) is synthesized directly from
glucose or as a final product of gluconeogenesis.

13. Proteins are sequences of amino acids (AA) linked by peptide bonds. There are twenty
amino acids of which nine are essential and eleven are non-essential. Essential amino
acids include phenylalanine, valine, threonine, tryptophan, isoleucine, methionine,
leucine, lysine, and histidine. These AA are essential because the body can’t synthesize
them. They must be present in the diet or they will be deficient. Four amino acids are
considered conditionally essential including arginine, tyrosine, glutamine, and cysteine.
Serine, glycine and proline are sometimes considered conditionally essential.
Conditionally essential AA are typically present, but in certain conditions may be
deficient.
PROTEINS

14. From the Mouth to the Stomach
The teeth begin the mechanical breakdown of the large pieces into smaller
pieces that can be swallowed. The salivary glands provide some saliva to
aid swallowing and the passage of the partially mashed through the
esophagus. The mashed pieces enter the stomach through the esophageal
sphincter. The stomach releases gastric juices containing hydrochloric acid
and the enzyme, pepsin, which initiate the breakdown of the protein. The
acidity of the stomach facilitates the unfolding of the proteins that still
retain part of their three-dimensional structure after cooking and helps
break down the protein aggregates formed during cooking. Pepsin, which
is secreted by the cells that line the stomach, dismantles the protein chains
into smaller and smaller fragments. Proteins are large globular molecules
and their chemical breakdown requires time and mixing.

15. From the Stomach to the Small Intestine
The stomach empties the chyme containing the broken-down
pieces into the small intestine, where the majority of protein
digestion occurs. The pancreas secretes digestive juice that
contains more enzymes that further break down the protein
fragments. The two major pancreatic enzymes that digest
proteins are chymotrypsin and trypsin. The cells that line the
small intestine release additional enzymes that finally break
apart the smaller protein fragments into the individual amino
acids. The muscle contractions of the small intestine mix and
propel the digested proteins to the absorption sites. In the lower
parts of the small intestine, the amino acids are transported from
the intestinal lumen through the intestinal cells to the blood.

17. FATS
Approximately 97% of dietary lipids are in the form of
triglycerides, and the rest are found as phospholipids and
cholesterol. Only small amounts of fat are digested in the mouth by
lingual lipase and in the stomach from the action of gastric lipase.
Gastric lipase hydrolyzes some triglycerides, especially shortchain
triglycerides (such as those found in butter), into fatty acids and
glycerol. However, most fat digestion takes place in the small
intestine as a result of the emulsifying action of bile salts and
hydrolysis by pancreatic lipase.

19. From mouth to the stomach
The first step in the digestion of triglycerides and
phospholipids begins in the mouth as lipids encounter
saliva. Next, the physical action of chewing coupled with
the action of emulsifiers enables the digestive enzymes to
do their tasks. The enzyme lingual lipase, along with a
small amount of phospholipid as an emulsifier, initiates
the process of digestion. These actions cause the fats to
become more accessible to the digestive enzymes. As a
result, the fats become tiny droplets and separate from the
watery components.

20. As stomach contents enter the small intestine, the digestive
system sets out to manage a small hurdle, namely, to combine
the separated fats with its own watery fluids. The solution to
this hurdle is bile. Bile contains bile salts, lecithin, and
substances derived from cholesterol so it acts as an emulsifier. It
attracts and holds onto fat while it is simultaneously attracted to
and held on to by water. Emulsification increases the surface
area of lipids over a thousand-fold, making them more
accessible to the digestive enzymes.
FROM STOMACH TO INTESTINE
Chylomicron
Chylomicrons Contain Triglycerides Cholesterol Molecules and
other Lipids.

21. Cholesterols are poorly absorbed when compared to
phospholipids and triglycerides. Cholesterol absorption is aided
by an increase in dietary fat components and is hindered by high
fiber content. This is the reason that a high intake of fiber is
recommended to decrease blood cholesterol. Foods high in fiber
such as fresh fruits, vegetables, and oats can bind bile salts and
cholesterol, preventing their absorption and carrying them out of
the colon.

22. LIPOPROTEINS

23. HORMONAL REGULATION OF BLOOD SUGAR/
GLUCOSE

24. Disorders of carbohydrate metabolism

25. DIABETES

26. LACTOSE INTOLERANCE
Lactose intolerance: a condition that results from inability to digest
the milk sugar lactose;
characterized by bloating, gas, abdominal discomfort, and diarrhea.
Lactose intolerance differs from milk allergy, which is caused by an
immune reaction to the protein in milk.

28. Lactase activity commonly declines with age. Lactase deficiency
may also develop when the intestinal villi are damaged by disease,
certain medicines, prolonged diarrhea, or malnutrition. Depending
on the extent of the intestinal damage, lactose malabsorption may be
temporary or permanent.
In extremely rare cases, an infant is born with a lactase deficiency.

30. Dietary Changes
Managing lactose intolerance requires
some dietary changes, although total
elimination of milk products usually is not
necessary. Excluding all milk products
from the diet can lead to nutrient
deficiencies because these foods are a
major source of several nutrients, notably
the mineral calcium, vitamin D, and the B
vitamin riboflavin.

31. Galactosemia
Galactosemia is a condition in which the body is unable to use (metabolize) the
simple sugar galactose.
A small amount of galactose is present in many foods. It is primarily part of a
larger sugar called lactose, which is found in all dairy products and many baby
formulas.

32. Causes:
Lactose in food (such as dairy products) is broken down by the
enzyme lactase into glucose and galactose. In individuals with
galactosemia, the enzymes needed for further metabolism of
galactose (Galactokinase and galactose-1-phosphate
uridyltransferase)
Are severely diminished or missing entirely, leading to toxic
levels of galactose or galactose 1- phosphate (depending on
which enzyme is missing) in various tissues.

34. Diagnosis:
Clinical manifestation including congenital cataract and presence
of galactose in urine as well as elevated blood galactose levels will
help in the diagnosis.
Treatment:
The only treatment for classic galactosemia is eliminating lactose
and galactose from the diet. Some individuals with galactosemia
experience long-term complications such as speech difficulties,
learning disabilities, neurological impairment (e.g. tremors, etc.).
Exclusion of galactose from diet causes reversal of major
symptoms but if brain damage occurs children may have normal
intelligence although they may have learning difficulty.

35. An inherited disorder characterized by failure to metabolize the
amino acid phenylalanine to tyrosine.
Phenylketonuria or PKU

37. metabolites (metabolic products) accumulate and damage
the developing nervous system. The impairment in the metabolic
pathway also prevents liver synthesis of tyrosine and
tyrosine-derived compounds (such as the neurotransmitter epinephrine).
Under these conditions, tyrosine becomes essential:
the body cannot produce tyrosine, and therefore the diet must
supply it.
Although PKU’s most debilitating effect is on brain development,
other symptoms may manifest if the condition is untreated.
Infants with PKU may have poor appetites and grow slowly. They
may be irritable or have tremors or seizures. Their bodies and
urine may have a musty odor. Their skin may be unusually pale,
and they may develop skin rashes. In older children and adults
who discontinue treatment, neurological and psychological problems
are common.

38. Maple syrup urine disease (MSUD)
Maple syrup urine disease (MSUD) is a lifelong and potentially life-
threatening inherited metabolic disorder. Metabolic disorders cause
problems with how your body breaks down food into the tiny components it
uses for energy. With MSUD, your body has trouble breaking down amino
acids, the building blocks of protein. People with MSUD have trouble
breaking down three amino acids in particular:
 Leucine.
 Isoleucine.
 Valine.

39. Symptoms
 A sweet, syrupy smell in their urine, sweat or earwax.
 Lethargy (they may move slowly or appear tired or weak).
 Irritability or fussiness.
 No appetite.