Transcript Homeostasis of the body

Human Nutrition
Digestive System
Nutrients:
Utilized or Stored Until Needed
Food Guide Pyramid
Diet and regular exercise
Nutrition - Macronutrients
Carbohydrates: major energy source,
simple or complex. Metabolic rate related
to glycemic index
 Lipids: cell components and energy
sources, saturated or unsaturated,
transfats, omega oils
 Proteins: 20 natural amino acids, building
and repair, hormones, enzymes
 Water: solvent, thermoregulation,
metabolic processes

Nutrition - Micronutrients
Vitamins: fat soluble and water soluble
 Minerals: recommended daily allowance
(rda)
 Fiber: some evidence decreases colon
cancer

Carbohydrates

General formula ratio is for most
carbohydrates is CH2O

Carbohydrate rich foods in their natural
state are low in calories and high in fiber
(AKA as cellulose, plant fibers we do not
digest).

Carbohydrates contain about 4 calories per
gram (fats about 9 cal per gram).
Simple Carbohydrates

Also called simple sugars.

Simple carbohydrates include
monosaccharides and
disaccharides such as:


fructose (fruit sugar),

sucrose (table sugar) and

lactose (milk sugar), as well as several other
sugars.
Simple carbohydrates are sources of quick
energy.
Complex Carbohydrates

Complex carbohydrates include fiber and
starches.

Found in vegetables, bread, rice, oatmeal,
whole grains, peas and beans.

Meats also provide carbs in the form of
glycogens.
Complex Carbohydrates

Complex carbohydrates take longer to be
digested, so your body needs more time to
release these carbs into your blood as
glucose.

This results in sustained energy (stamina).

SEE GLYCEMIC INDEX
Undigestible Complex Carbohydrates

Also called fiber

Essential role in large
intestine health

“Brushes” walls of
large intestine
Carbohydrates
•
•
•
When we eat carb rich foods, our blood
glucose levels increase dramatically.
our pancreas secretes insulin so that
glucose units can be taken into body cells
for use in respiration (producing ATP).
Insulin and diabetes
Blood Sugar
•
In times of not eating, our brain still needs
glucose, our muscles still need glucose
•
This stimulates the pancreas to produce
the hormone glucagon which converts
glycogen stored in the liver into glucose.
•
If there is still insufficient glucose, the liver
metabolizes fats and converts these
molecules into glucose.
Glucose to Glycogen
Glycemic Index

High glycemic foods are used quickly and
stored as fat tissue easily.

Low glycemic foods provided more long
term energy and reduced insulin levels
(which is a good thing).
Glycemic Index

The effect of eating high glycemic index
foods consistently is to lead to constantly
high insulin levels.

In this situation, the body becomes
accustomed to these high insulin levels and
starts to respond to them less effectively
over time.
Glycemic Index

As high glycemic index foods are eaten
further, this progresses, more and more
insulin is required to have the same effect
on the tissues.

This phenomenon is known as insulin
resistance, and is the first step towards
diabetes.
Glycemic Index
High
glycemic index
Medium
glycemic index
Low
glycemic index
Maltose (beer)*
Rye bread (crispbread)
Oatmeal porridge
Cooked parsnips
Muesli (no sugar)
Wholewheat pasta
Cooked carrots
Brown rice
Sweet potato
White Rice
Cooked beets
Dried Peas
Biscuits / cookies
Garden peas
Apples
Baked potato
Boiled potato
Pears
Cornflakes / cereal
Wholewheat bread
Whole milk
Bagels
Corn, polenta
Kidney beans
White Bread
Sultanas / raisins
Lentils
Corn chips
Orange juice
Soybeans
Mangoes
Oatmeal biscuits / cookies
High water content fruits (melon etc)
Ripe bananas
White pasta
Apple juice
Papaya
Buckwheat
black-eye peas
Rice cakes
Pinto beans
Green vegetables
Lipids

Triglycerides have the general elements
are C, H, O like carbs except they have
much less O. They are made of glycerol
and fatty acids.

Glycerol is a small, 3-carbon molecule with
three hydroxyl groups.
Lipids

Fatty acids are long molecules with a polar,
hydrophilic end and a non-polar,
hydrophobic "tail". The hydrocarbon
chain can be from 14 to 22 CH2 units long
*even number of C.
Saturated Fats

If there are no C=C double bonds in the
hydrocarbon chain, then it is a saturated
fatty acid (i.e. saturated with hydrogen).

These fatty acids form straight chains, and
have a high melting point.

Sources are animals:

butter and

lard (solid at room temp.)
Unsaturated Fats

If there are C=C double bonds in the
hydrocarbon chain, then it is an
unsaturated fatty acid (i.e. unsaturated
with hydrogen).

These fatty acids form bent chains, and
have a low melting point.
Unsaturated Fats

Fatty acids with more than one double
bond are called poly-unsaturated fatty
acids (PUFAs).

Cold blooded animals (fish) and plants are
sources: omega fatty acids, flax, olive oil,
canola and sunflower oil.
Triglycerides

Triglycerides are insoluble in water.

They are used for storage, insulation and
protection in fatty tissue (or adipose tissue)
found under the skin (sub-cutaneous) or
surrounding organs.

They yield more energy per unit mass than
other compounds so are good for energy
storage (about 2X more energy).
DIETARY CONSIDERATIONS

In food chemistry, HYDROGENATED
margarine is plant unsaturated fatty acid
which has had H added back to its
structure.

This results in a margarine which is more
solid and able to with-stand higher
temperatures.

Most unsaturated fats are liquids (olive oil,
canola oil are liquid at room temperature).
DIETARY CONSIDERATIONS

TRANS FATS: Unsaturated fats have a
structure with kinks; these kinks result in a
liquid state at room temperature.

In the early 20th century, a chemical
process called hydrogenation was
developed that converts vegetable oils into
saturated, more solid fats (margarine and
vegetable shortening).
DIETARY CONSIDERATIONS

When it was discovered that eating
saturated fats increases the risk for
coronary heart disease, the food industry
turned to partial hydrogenation.

This process lowered the content of
saturated fat in vegetable shortening and
margarine, but also dramatically increased
the amount of a certain kind of fat - trans
fat - in our diets, as an unavoidable side
reaction.
DIETARY CONSIDERATIONS

While suppliers praised processed
vegetable oils as healthy unsaturated and
cholesterol-free substitutes for animal fats,
there is now strong evidence that
introducing trans-fatty acids into our diets
does more harm than good.
Phospholipids

Phospholipids have a similar structure to
triglycerides, but with a phosphate group
in place of one fatty acid chain.

There may also be other groups attached
to the phosphate.
Phospholipids

Phospholipids have a polar hydrophilic
"head" (the negatively-charged phosphate
group) and two non-polar hydrophobic
"tails" (the fatty acid chains).

This mixture of properties is fundamental to
biology, for phospholipids are the main
components of cell membranes.
Waxes

Waxes are formed from fatty acids and
long-chain alcohols.

They are commonly found wherever
waterproofing is needed, such as in
 leaf
cuticles,
 insect
 birds'
exoskeletons,
feathers and
 mammals'
fur.
Waxes - Cholesterol

CHOLESTEROL is like a fatty wax.
Normally made in the liver, it is structural
component of nerve tissue and cell
membranes.

It is also used to make various steroid
hormones including progesterone,
testosterone (sex hormones in females and
males) estradiol, and cortisol.

Bile salts are breakdown products of
cholesterol.
Waxes

Blood is watery, and cholesterol is fatty.
Just like oil and water, the two do not mix.

To travel in the bloodstream, cholesterol is
carried in small packages called
lipoproteins.

The small packages are made of fat (lipid)
on the inside and proteins on the outside.

Two kinds of lipoproteins carry cholesterol
throughout your body.
Waxes

It is important to have healthy levels of
both:

Low-density lipoprotein (LDL) cholesterol
is sometimes called bad cholesterol.

High amounts of LDL cholesterol leads to a
build up of cholesterol in arteries.

The higher the LDL level in your blood,
the greater chance you have of getting
heart disease.
Waxes

These form plaques along arteries.

When it hardens the arteries we call it
arteriosclerosis.

These can dislodge to plug smaller arteries
or veins—heart attacks or strokes are
possible.

They can completely block a vessel
resulting in an embolism, aneurism, heart
attack, stroke.
Waxes

Waxes

High-density lipoprotein (HDL)
cholesterol is sometimes called good
cholesterol.

HDL carries cholesterol from other parts of
your body back to your liver.

The liver removes the cholesterol from your
body.

The higher your HDL cholesterol level, the
lower your chance of getting heart
disease.
The cholesterol numbers:
Things that TEND to increase LDL levels:

Overweight

Physical inactivity•

Cigarette smoking

Excessive alcohol use

Physical inactivity

Very high carbohydrate diet

Certain diseases and drugs

Genetic disorders.
What seems to be the population trend:
Proteins
 The
polymer of amino acids does not
remain like a long chain but folds into a
three-dimensional shape which is the
most stable for that sequence of amino
acids.
 This
shape is called the native
conformation for that particular protein
and is essential for that protein's biological
activity. i.e. shape is everything
Proteins

The shape may be altered by various
factors e.g. heat or large pH changes.
 Once
the three-dimensional shape is
altered, biological activity is lost.
 The
building blocks of proteins are amino
acids
 These
are arranged in a very specific
order – determines shape
Essential & Non-Essential AA’s

As far as your body is concerned, there are
two different types of amino acids:

essential and non-essential.

Non-essential amino acids are amino acids
that your body can create out of other
chemicals found in your body.

Essential amino acids cannot be created, and
therefore the only way to get them is through
food.
Protein

Protein in our diets comes from both
animal and vegetable sources. Most
animal sources (meat, milk, eggs) provide
what's called "complete protein," meaning
that they contain all of the essential amino
acids.

Vegetable sources usually are low on or
missing certain essential amino acids. For
example, rice is low in isoleucine and
lysine.
Balancing AA’s

However, different vegetable sources are
deficient in different amino acids, and by
combining different foods you can get all of
the essential amino acids throughout the
course of the day.

This balancing of amino acids is essential
because if one amino acid is deficient, an
entire protein cannot be made sufficiently.
Vegetarian Diets

Vegetarians need to balance plant source
proteins—eg. Rice with beans.

Some vegetable sources contain quite a bit
of protein -- things like nuts, beans,
soybeans, etc. are all high in protein. By
combining them you can get complete
coverage of all essential amino acids.
Types of Vegetarian Diets

Pescatarian – may include fish but no
chicken, beef, pork

Flexitarian – may include some meat time
to time

Lacto-Ovo vegetarian – includes milk
products and eggs but no meats

Vegan – do not include any animal
products including processed foods that
may include animal products like gelatine,
honey.
To Get Protein RDA

The digestive system breaks all proteins
down into their amino acids so that they
can enter the bloodstream.

Cells then use the amino acids as building
blocks.

This photo is the
Nutritional Facts label
from a can of tuna.

According to the RDA (Recommended
Daily Allowance) for protein is 0.36 grams
of protein per pound of body weight. So
a 150-pound person needs 54 grams of
protein per day.

From this you can see that your body
cannot survive strictly on carbohydrates.
You must have protein.
Nutritional label from a can of tuna fish

You can see that a can of tuna contains
about 32 grams of protein (this can has 13
grams per serving and there are 2.5
servings in the can).

A glass of milk contains about 8 grams of
protein.

A slice of bread might contain 2 or 3 grams
of protein.

You can see that it is not that hard to meet
the RDA for protein with a normal diet.
Role of Insulin
Insulin
is a simple protein in which two
polypeptide chains of amino acids are joined
by disulfide linkages.
It
transfers glucose into cells to produce
energy for the body.
In
adipose (fat) tissue, insulin facilitates the
storage of glucose and its conversion to fatty
acids.
Role of Insulin
•
Insulin also slows the breakdown of fatty
acids.
•
In muscle it promotes the uptake of amino
acids for making proteins.
Role of Insulin

In the liver it helps convert glucose into
glycogen (the storage carbohydrate of
animals) and it decreases
gluconeogenesis (the formation of
glucose from noncarbohydrate sources like
fat or protein).

The action of insulin is opposed by
glucagon, another pancreatic hormone,
and by epinephrine.
If glucose levels remain high, the liver:

stores the sugars as glycogen (animal
starch).

If the glycogen is not used up, it further
metabolizes glycogen into fatty acids and
fat molecules.

These are transported around the body in
blood vessels and lymphatic vessels and is
stored in ADIPOSE tissue (fat tissue) until
needed.
If glucose levels remain high, the liver:

This provides smoothness under the skin,
protection, and a secondary source of
energy when needed—not all fat is bad.

If we don’t use it regularly though, it builds
up into unhealthy situations such as fatty
tissue around the heart and in the blood
vessels. (Long Term Storage)
Disposal by Various Tissues of a Hypothetical Meal Containing 100 g of Glucose
http://www.medscape.com/infosite/diabetes_education/article-3
Extreme starvation situations (dieting)

After immediate energy sources are used
(like carbohydrates—including stored
glycogen converted to blood sugar), fat
reserves are used.

After fat reserves are used, the body
begins to “call-up” proteins. Proteins are
converted into an energy source as a last
resort.
Extreme starvation situations (dieting)

This is damaging to our protein rich tissues
(muscles, hair, nails) and we notice the
differences in our eyes, nails, hair and skin
texture.

It also damages skeletal muscles and heart
muscle. These damages are not easily
reversed by “proper” dieting later.
PRIORITIZED SOURCES OF ENERGY

Sugars

Fats

Proteins

This site slightly detailed metabolic
pathways that describe biochemical
processes in metabolism:

http://users.humboldt.edu/rpaselk/BiochSup
p/PathwayDiagrams/PathIndex.html
1991 study published in the "The American Journal
of Clinical Nutrition"

Showed that patients following a very lowcalorie diet

lost lean body mass and experienced a
decrease in metabolic rate after only three
days.

Then, 21 days after the start of the diet,
participants experienced an 18 percent
decrease in metabolism and lean body mass,
on average.
Read more:
http://www.livestrong.com/article/486748dieting-muscle-atrophy/#ixzz1eyOOO3A7
GENERAL PRINCIPLES OF WEIGHT
CONTROL

Body weight is always the result of a simple
equation. Input vs. Output = Body Weight

Input refers to the amount of food
consumed.

Output refers to the amount of energy
expended.
GENERAL PRINCIPLES OF WEIGHT
CONTROL

Therefore, if Output = Input you will
maintain your present weight.

If Input is less than Output you will lose
weight. If Input is greater than Output
you will gain weight.

There is no short cut to weight loss.

One pound of body weight = 3,500 kcal
or 32,000kj.
GENERAL PRINCIPLES OF WEIGHT
CONTROL

In order to reduce body weight you must do
one of the following:

Decrease food intake

Increase activity

Do a combination of both (this is most
effective)
The problem with diets

Nutrition

Abnormal (not a lifestyle change)

Loss of muscle mass
E.g. -A person who diets and loses 10 lbs.
loses both fat and muscle tissue.
-When these 10 lbs are regained they
are in the form of just fat tissue.
-The person now has more fat tissue
than before the diet even though their
weight is the same as at the outset.
GENERAL PRINCIPLES OF WEIGHT
CONTROL

All weight loss is the result of a loss in
muscle and fat tissue.

To offset this loss of muscle mass exercise
must accommodate any weight loss
program.

An increase in exercise does two things to
aid in weight loss:

It increases caloric expenditure.

It increases metabolism by increasing muscle
mass
 i.e.
A larger engine burns more fuel.
A recommended program would be:

Decreasing intake by 200 kcal/day

Increasing activity by 300 kcal/day

500 kcal/day = 3,500 = 1 lb/wk.

Any successful weight loss program must
be a lifestyle change not a fad.

Exercise must accommodate diet in order
to offset muscle loss and increase
metabolism.