The document discusses the process of nutrition, detailing how food is digested and nutrients are absorbed in the human body. It explains the roles of various enzymes and hormones in breaking down carbohydrates, proteins, and fats, and outlines the functions of the small and large intestines in nutrient absorption and waste elimination. The importance of intestinal flora, including probiotics, in maintaining health is also highlighted.

1. The Science Behind Health
With Doctor Bones (Don R. Mueller, Ph.D.)
The Funny Man of Health
Educator
Entertainer
J
U
G
G
L
E
R
Scientist

2. Nutrition: is the process by which humans obtain
energy and nutrients in the form of foods and drink for
normal functioning, growth and repair. Good nutrition
means satisfying the biochemical needs of the body.
Nutrition is also the study of food and diet.
Nutrition may be viewed as a simple 3-Step process:
Step 1: Eating and Drinking. That seems fun and easy.

3. Step 2: Your body breaks down food into nutrients:
1. Carbohydrates become simple sugars,
2. Proteins become amino acids,
3. Fats become fatty acids and glycerol,
4. Vitamins and minerals are released.
We start our journey with the breakdown of
carbohydrates into simple sugars. This initiates
in the mouth where the enzyme amylase
starts digesting the carbohydrates (starches)
from our meal. Amylase is secreted by the
salivary glands.

4. Amylase breaks the carbohydrates (starches) from our meal into
smaller polysaccharides along with the disaccharide sugar called
maltose, which is constructed from two glucose molecules.
Starch polysaccharides +
maltose
Amylase
Enzymes are chemical “catalysts.” They are protein-based
molecules, which catalyze biochemical reactions taking place in
the body. They influence the rates of biochemical processes by
lowering the activation energies for these reactions.

5. Once the food or "ingesta" as it is now called, moves into the
stomach, the excitement really begins. Gastric juices start the task
of digesting food as the stomach churns. Gastric juices include
hydrochloric acid (HCl) and enzymes called proteases and lipases.
Proteases, like pepsin, for example, are enzymes that help
breakdown proteins into peptides and amino acids.
Proteins Peptides Amino Acids
proteases peptidases

6. Lipases are enzymes that help in breaking down fats (triglycerides)
into mono- and diglycerides. This “soup” of gastric secretions and
partially digested food (also known as chyme) passes through the
pyloric sphincter (a type of valve between the stomach and the
small intestine) and moves into the small intestine.
The fat molecules, also called
triglycerides are then broken
down to fatty acids and
glycerol by lipases. These fat-
specific enzymes attack the
bonds between glycerol and
the respective fatty acids in
the fat molecule in a process
called hydrolysis, which adds
H2O across these bonds.

7. The acidified ingesta entering the small intestine stimulates the
release of secretin, a hormone secreted by epithelial cells in the
wall of the small intestine, which in turn, stimulates the release
of bicarbonate-rich fluids from the pancreas and liver.
The bicarbonate solution neutralizes the acidic ingesta in the
same way that sodium bicarbonate (NaHCO3 or "baking soda")
from an Alka-Seltzer tablet neutralizes stomach acid.
Interestingly, the mucous cells lining the stomach wall also
secrete bicarbonate-rich mucus, which protects the stomach
itself from being digested by hydrochloric acid.
The final stages of the enzymatic digestion of food occur in the
small intestine. It is through the small intestine that the
nutrients we obtain from foods are largely absorbed. The small
intestine comprises three sections, which in order of appearance
from the stomach are the duodenum, jejunum and ileum.

8. The duodenum is short, but receives important secretions,
including an assortment of pancreatic enzymes and bile from
the liver via bile ducts. The jejunum is roughly 40% of the small
intestine in humans. The ileum is the remainder of the small
intestine and empties into the large intestine.
Bile is a complex mixture of water, various salts (electrolytes),
bile acids, cholesterol, phospholipids and bilirubin. Bilirubin is a
waste product resulting from the breakdown of hemoglobin
molecules from old red blood cells (erythrocytes). Bile acids
(also called bile salts) are important cholesterol derivatives
synthesized in the liver. Their importance comes from the fact
that bile acids behave much like a detergent does in dissolving
fats in water solutions. Once the fats are dissolved in a process
known as emulsification they can be digested by lipases
secreted by the pancreas and absorbed by the small intestine.

9. Bile Salts Emulsify Fats
Fat
Bile
Salts
Bile acids also facilitate the absorption of fat-soluble vitamins
through the small intestine and aid in the elimination of excess
cholesterol from the body. About 5% of bile acids end up in the
feces, while the remainder are recycled through the ileum.

10. The Amazing Small Intestine
The small intestine is where amino acids and simple sugars are
absorbed. The bulk of the minerals that we need are also
captured via the small intestine.
Trypsin and chymotrypsin are two of the major proteolytic
(protein digesting) enzymes secreted by the pancreas. They cut
proteins into medium to small peptides, which can then be
cleaved into amino acids by a family of aminopeptidase enzymes
also secreted by the pancreas.
Pancreatic amylase converts starch into the disaccharides,
maltose, sucrose and lactose. These sugars are then cleaved by
their respective enzymes, maltase, sucrase and lactase. People
who are lactose (milk sugar) intolerant either lack the enzyme
lactase or have too little of it for the proper conversion of lactose
into glucose and galactose. Try “Lactase” Milk.

11. The inner surface (called the
lumen) of the small intestine is
not smooth, but instead is
covered with millions of finger-
like projections called villi,
which significantly increase the
surface area of the small
intestine. Quite ingenious.
Villi Anatomy
Glucose is absorbed through the epithelial cells lining the villi of
the small intestine. Actually, glucose is absorbed along with
sodium, which binds to glucose via a sodium-dependent hexose
transporter in a process known as active transport.

12. Pumping glucose molecules
and sodium ions (Na+) across
the epithelial cell membrane
and against a change in
solution concentration (known
as a gradient or "slope") is
called active transport.
This process requires energy in
the form of ATP. From here,
glucose enters the blood to be
carried to the individual cells
of the body, thus satisfying
their energy needs.
Active transport

13. The villi are lined with epithelial cells, whose exposed surface has
hundreds of tiny, hair-like projections called Microvilli. The
microvilli further increase the surface area of the small intestine
thus contributing to a much-enhanced absorption of nutrients.
Viewed through a microscope, the closely packed microvilli look
sort of like a brush, hence the name "brush border" is used to
describe their appearance.
Epithelial Cells of the Small Intestine
Microvilli
Cytoplasm
Nucleus
Mitochondrion

14. The large intestine functions
largely like a septic system in
eliminating waste products
(i.e., bacteria and indigestible
foods) from our body.
The last portion of the small
intestine (ileum) is separated
from the first part of the large
intestine (cecum) by the
ileocecal valve, which prevents
materials in the large intestine
from backing up into the small
intestine.
The Amazing Large Intestine
Transverse
Colon
Ascending
Colon
Descending
Colon
Ileum
Sigmoid
Colon
Cecum
RectumAppendix
Anal Canal

15. The large intestine in humans has three primary functions:
1. Reabsorption of water and electrolytes such as sodium.
2. Bacterial fermentation.
3. Packaging waste materials for disposal.
The large intestine reclaims much of the water used in digestion in
order to avoid dehydration of the body. In the case of diarrhea, for
example, the large intestine is forced to discharge waste products
before the water reabsorption process is complete.
Constipation, on the other hand, occurs when the large intestine
retains waste products for too long. Waste materials basically dry
out to the point where they become hard to pass. When Mother
Nature calls we struggle to get the job done. It is then that we are
truly in need of intestinal fortitude.

16. The large intestine is a miniature ecosystem teeming with various
bacteria, intestinal yeasts and fungi, along with a host of other
microbes, which come together to produce the "intestinal flora" as
we know it.
Many of the intestinal bacteria are "friendly" like lactobacillus
acidophilus and bifidobacteria (bifidus), which are also known as
probiotic bacteria. Probiotics has been defined as the ingestion by
the host, live microorganisms in amounts that produce a health
benefit for the host.
Although most probiotic microorganisms are bacteria, the yeast
Saccharomyces boulardii has been given probiotic status.
Saccharomyces boulardii (S. boulardii) is used, for example, to
prevent diarrhea linked to the use of antibiotics.

17. We need these friendly intestinal microorganisms to help defend
us against harmful bacteria and other pathogenic organisms and
toxins. A healthy intestinal flora not only boosts our immune
system, there is also evidence to suggest that friendly intestinal
microbes aid in the elimination of pre-carcinogenic or mutagenic
compounds from the body.
Intestinal bacteria can also affect the synthesis and metabolism of
certain vitamins (K, B12, biotin and folic acid). Vitamin K is known
as the anti-hemorrhagic vitamin and is synthesized by intestinal
bacteria.
Step 3: Nutrients are transported via the blood to all parts of
your body where they are taken up by the cells and used as
energy or for the construction or "synthesis" as it is called, of
other compounds needed by the body.