The Body’s Building Blocks


Which of the food groups from the
Food Pyramid provide the most
protein in a diet?
Answer: The meat/beans group and
the milk products group




It is an energy-yielding nutrient composed of
carbon, hydrogen, oxygen, and nitrogen
The presence of nitrogen is what makes it
differ from carbohydrates and fats
Proteins are made up of amino acids
The body has at least 30,000 types of
proteins; each type does a different job



The building blocks of protein
Most proteins are made up of different
patterns and combinations of 20 amino acids,
which are linked in strands
The 20 amino acids are like letters in the
alphabet – just as you use different letter
combinations in different sequences to make
different words, you combine different amino
acids in different sequences to make different
proteins


Every cell contains DNA; this DNA provides
the instructions for how the amino acids will
be linked to form the proteins in your body
In this way, your body can take amino acids
from the breakdown of foods that you eat
and make the required proteins to perform
required body functions, such as tissue and
cell repair, disease fighting, growth and
development, etc.


DNA is to proteins, as ____ is to a model
airplane kit
Amino acids are to proteins, as ____ are to
the alphabet


Proteins can change their shape and take on
new characteristics
This is called denaturation
 Heat, acids, bases, and alcohol are among the
factors that can denature proteins
 E.g. : Frying an egg – applying heat to an egg
changes it from a runny fluid to a solid mass
 The shapes of the protein molecules in the egg
have changed
 Once a protein is denatured, it can never return to
it’s original state




You need all 20 amino acids for good health
Your body can synthesize 11 of the amino
acids from other amino acids
The amino acids your body can make are
called nonessential amino acids
The remaining 9 amino acids that your body
can’t make are called essential amino acids


What is the difference between essential
amino acids and nonessential amino acids?
Answer: Your body can make nonessential
amino acids, while it has to obtain essential
amino acids from foods




Bite, chew, swallow
Stomach acids denature the protein
Move to the small intestine, where they are
broken down by enzymes into single amino
acids
Amino acids are absorbed into the
bloodstream, and are carried to the body cells
that need them





Your cells can use amino acids from food
proteins to build new proteins
Cells can also convert amino acids to other
compounds, including other amino acids
The proteins built by cells are custom
designed to perform a wide range of
functions
The roles proteins play depend on where they
are located and how your body needs them
Proteins have 6 main functions



As your body grows, it uses protein to help
make new tissue, which is why it is important
for people to get enough protein during the
growth years
When you eat a nutritious diet, your body
uses protein to build lean muscle mass
Protein makes up about 18-20% of the body
◦ About 3% of this protein is broken down each day
◦ You also need protein to maintain existing tissue



Your body uses proteins to make enzymes,
which cause specific chemical reactions in the
body (e.g. digestive enzymes for food
breakdown)
Proteins are used to make some hormones,
which are released in the bloodstream to
control specific body processes
Your body’s immune system uses proteins to
make antibodies, which defend the body
against infection and disease



Proteins help carry the minerals sodium and
potassium from one side of cell walls to
another
These minerals and other proteins control the
flow of water through cell membranes
A balance of fluid inside and outside the cell
is crucial



Acid-base balance refers to the maintenance
of the correct level of acidity of a body fluid
If blood becomes too acidic, it can be lifethreatening
Proteins in the blood act as chemical buffers
◦ A buffer is a compound that can counteract an
excess of acid or base in a fluid



Proteins linked with fat form lipoproteins,
which are the compounds used to carry fats
in the bloodstream
Proteins also transport iron and other
nutrients
Oxygen transport in the blood is reliant upon
protein as well




The body’s number one priority is to provide
the cells with the energy they need to exist
Even though only proteins can perform cell
growth and repair, the body will use proteins
for energy when it lacks carbs and fats
The body will also burn proteins for energy
when there is excess protein taken in; this is
hard on the liver and kidneys
* A Billboard For Proteins



Animal flesh – Beef, pork, poultry, lamb, veal,
and fish
Other sources – Eggs, milk, yogurt, cheese,
and ice cream
Meat and some dairy are problematic due to
high fat content
◦ Most of the fat is saturated
◦ No fiber is obtained from these foods
◦ The cost of protein from animal sources can be
high



Found in grains, nuts, seeds, and legumes
Legumes are peanuts, black-eye peas, kidney
beans, black beans, chickpeas, etc.
Soy beans are a large source of plant protein
◦ They are a legume
◦ They can be modified to form a variety of food
products, such as tofu and soy burgers



The practice of eating a diet
consisting entirely or
largely of plant foods
Beneficial to health in that
most of the fat in plant
foods are polyunsaturated,
plants foods contain no
cholesterol, and these
foods are generally high in
fiber
The eating patterns of
vegetarians vary greatly;
there are four main types




1. Vegans – eat no food from animal sources; their
diet is limited to plant foods
2. Lacto-vegetarians – eat animal protein in the
form of dairy products, but no meats, fish, poultry,
or eggs
3. Lacto-ovo vegetarians – eat animal protein in the
form of dairy and eggs, but no meats, fish, or
poultry
4. Semivegetarians – eat dairy, eggs, poultry, and
seafood, but no red meat





Religious reasons – Buddhists, Hindus,
Seventh-Day Adventists, Trappist monks
Health reasons – avoid fat and cholesterol,
hormones and chemicals, and foodborne
illnesses
Socioeconomic reasons – eating meat is
wasteful
Environmental reasons – animal grazing is
hard on the land
Humanitarian reasons – can’t stand the idea
of eating Bambi, Flipper, Chicken Little, etc.

Proteins in different foods differ in quality
◦ Plant foods provide lower quality proteins and are
sources of incomplete proteins
 These proteins are missing one or more of the
essential amino acids
◦ Animal foods have high quality proteins and are
sources of complete proteins
 Means that all the essential amino acids humans need
are present in the proteins
 Animal products such as eggs, cheese, milk and yogurt
are also complete proteins




Your body needs the right balance of all 20
amino acids to build tissues and other
compounds
If one or more essential amino acids is
missing your cells will not be able to make
needed proteins
Have to find a way to complete the
incomplete proteins
*Animal Vs. Plant Protein





You can get the amino acids missing from one
incomplete source by combining it with another
incomplete source
Two or more incomplete proteins which can be
combined to provide all the essential amino acids are
called complementary proteins
In general, combining grains, nuts, or seeds with
legumes will give you complementary proteins (e.g.
peanut butter and whole wheat bread)
Can also get a complete protein when eating a small
amount of a complete protein with a large amount of
an incomplete protein (e.g. pork with rice)
* A Good Match


Your body does not store protein, so you
need some every day
The amount depends upon your age, gender,
body size, and health
◦
◦
◦
◦

Children and teens need more
Pregnant and nursing women need more
Teenage boys and men need more
Sick and injured people need more
Why do the above groups need more?






Children need more protein due to rapid
growth
Pregnant women need more protein for fetal
development
Nursing mothers need more to make milk
Males need more due to a higher amount of
muscle mass
People who are sick need more in order to
make antibodies
People who are injured need more to repair
damaged tissue



14-18 year old males – 52 grams per day
14-18 year old females – 46 grams per day
To meet the RDA, 10-35% of daily calories
should come from protein (do the math)



Well-trained athletes do need a little more
protein per day
An extra half a glass of milk or a chicken
wing will provide the extra that athletes need
Remember – an athlete’s primary need is for
energy
◦ Athletes should focus on the high end of the calorie
range for carbs (~55-65%) and the low end of the
range for fats (~20-25%)
◦ That leaves 10-25% of an athletes calories for
protein



So much of what is out there is unproven
Not enough research at this point, so long
term effects are still largely unknown
(transparency)



As with all nutrients, moderation is key
Nitrogen balance is a comparison of the nitrogen a
person consumes with the nitrogen they excrete
Protein is the only nutrient that provides nitrogen, so
nitrogen balance is used to evaluate a person’s
protein status
◦ Nitrogen equilibrium – take in as much as you excrete
(e.g. healthy adult)
◦ Positive nitrogen balance – take in more than you
excrete (e.g. when you are growing tissue, such as a
child or a pregnant woman)
◦ Negative nitrogen balance – take in less than you excrete
(e.g. losing body tissue due to starvation)
◦
* Protein Balance



Deficiency diseases develop when you lack an
essential nutrient
Common among people fighting poverty
Protein-energy malnutrition (PEM) – condition caused
by a lack of calories and protein in the diet
◦ Kwashiorkor – protein-deficiency disease; common in
poor countries when a mother weans one child to feed
the next; characterized by stunted growth and immune
system weaknesses
◦ Marasmus – calorie and protein – deficiency disease;
most often affects infants in poor countries;
characterized by wasting away of the body and infant
mortality


Most people in the U.S. consume too much protein
Leads to:
◦ Liver and kidney problems – excess proteins must be
excreted as nitrogen; overworks the liver and kidneys,
causing them to age prematurely
◦ Calcium loss – diets high in protein from animal sources
contribute to calcium loss from the bones, leading to
fractures, osteoporosis, etc.
◦ Excess body fat – many high-protein foods are also
high-fat foods; since the body cannot store excess
protein, it converts it to fat and stores it in the adipose
tissue, leading to weight gain
◦
* Not Too Little, Not Too Much








4 ounces extra-lean
ground beef patty
290 calories
112 mg cholesterol
High in saturated fat
0 g fiber
44% protein
56% fat
0% carbohydrates








½ cup pinto beans
116 calories
0 mg cholesterol
Low in saturated fat
7 g fiber
24% protein
1% fat
75% carbohydrates




What is the difference between an essential
and a nonessential amino acid?
What role do stomach acids play in protein
digestion?
How can a diet low in carbohydrates and fats
affect the way the body uses proteins?
Name three specific animal sources and three
specific plant sources of protein.



About what percentage of daily calories
should come from protein?
What type of nitrogen balance would describe
the protein status of a healthy teen?
What are the 3 problems associated with
high-protein diets?