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PROTEINS
Proteins are necessary for building the structural components of the
human body, such as muscles and organs. You also need proteins to
keep your immune system healthy, synthesize neurotransmitters,
create and signal hormones, and much more. A balanced diet
supplies you will all of the protein you need. Meats, eggs, and dairy
products are significant sources of protein, but you can also get
protein from a variety of grains, legumes, nuts, and seeds.
Just a Tiny Bit of Protein Chemistry
Proteins tend to be large molecules made up of several building
blocks called amino acids. The general structure of any amino acid
molecule includes a carboxyl group of atoms, an amine group and a
side chain. The carboxyl group contains one carbon, two oxygen, and
one hydrogen atom. The amine group contains one nitrogen atom
with two hydrogen atoms attached to it.
All 20 amino acids have different side chains, which vary in shape
including straight chains of atoms, branched chains of atoms and
rings of atoms. The side chains may include carbon, hydrogen, sulfur,
nitrogen and oxygen atoms. The configuration and molecules found in
the side chain is what differentiates one amino acid from another.
The branched-chain amino acids are isoleucine, leucine, and valine.
These amino acids are necessary for muscle structure. Tyrosine,
phenylalanine and tryptophan are called aromatic amino acids. Each
one contains a side chain with a ring-shaped formation. These three
amino acids are needed for neurotransmitter production.
There are 20 different amino acids. Amino acids are linked together
to form peptides, which are small chains of amino acids. The peptides
are then linked together to form larger proteins.
There are thousands of different proteins that carry out a large
number of jobs in the human body. Even though so many different
proteins are at work in your body, you don't have to worry about
consuming each individual protein from the foods you eat. Your body
will make those proteins. All you need to do is to make sure your
body has a healthy supply of all 20 of the different amino acid
"building blocks." Having enough of those amino acids is easy
because your body can make 11 of them from other compounds
already in your body. That leaves eight amino acids that you must
get from your diet. Those eight amino acids are called "essential
amino acids."
Non Essential and Essential Amino Acids
The 11 non-essential amino acids are not called "non-essential"
because they are not important. They are important and your body
requires them to perform several functions. These amino acids are
called "non-essential" because you don't need to get them from your
diet. Your body can build those 11 amino acids from chemicals
already present in your body. The non-essential amino acids include:
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Alanine
Arginine
Asparagine
Aspartic Acid
Cysteine
Glutamic Acid
Glutamine
Glycine
Proline
Serine
Tyrosine
The amino acids arginine, cysteine, glycine, and tyrosine are
sometimes also considered to be "conditionally essential." That
means most people manufacture them on their own, but some with
certain illness or genetic abnormalities don't and need to get them
through their diets.
The nine essential amino acids are called "essential" because you
can't manufacture them, you have to eat proteins that contain those
amino acids. Those essential amino acids include:
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Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
Do you really need to worry about essential amino
acids when you plan your daily meals?
Not really. Animal sources of protein such as meat, eggs, and dairy
products are "complete proteins." That means that each protein found
in an animal product contains each of the nine essential amino acids.
Vegetarians and vegans may need to pay a little more attention to
the dietary proteins. Plant proteins are called "incomplete proteins."
Each plant protein is missing at least one of the nine essential amino
acids. However, every amino acid is found in some type of plant, so
you can combine different plant proteins to get all of the amino acids
you need. We will get back to this later in the lesson.
Protein Functions in the Body
There are many different proteins in your body, and they perform
different functions. Proteins functions include:
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Contributing to enzyme activity that promotes chemical
reactions in the body
Signaling cells what to do and when to do it
Transporting substances around the body
Keeping fluids and pH balanced in the body
Serving as building blocks for hormone production
Helping blood clot
Promoting antibody activity that controls immune and
allergy functions
Serving as structural components that give our body parts
their shapes
Protein Digestion and Metabolism
The digestion of protein begins in the mouth with chewing. Chewing
not only makes food easier to swallow, it also helps with digestion by
chopping food up into smaller bits. Remember that it really is
important to chew your food thoroughly; don't gulp your food down in
huge bites.
Protein digestion continues in the stomach with the release of
hydrochloric acid and pepsinogen. Hydrochloric acid converts
pepsinogen into pepsin, which begins to break down the bonds
between the amino acids. This process takes place while the muscles
surrounding the stomach squeeze and squish the foods and stomach
fluids together.
The next step occurs in the small intestine where the hydrochloric
acid is neutralized with bicarbonates released from the pancreas. The
pancreas also releases an enzyme called trypsin. Trypsin continues to
break apart the amino acids, which are then absorbed into the blood
stream. Once in the bloodstream, the amino acids are carried to the
cells in various parts of your body. Your body uses the individual
amino acids that were broken down during digestion to build the
proteins needed for the various functions.
You may not think of protein as an energy source, but proteins do
contribute calories to you diet. Those calories need to be
acknowledged if you are watching your weight. Each gram of protein
you eat has four calories. The USDA suggests that you get about 15%
to 20% of your calories from protein. For someone who needs 2000
calories per day, that would equal 75 to 100 grams of protein.
It isn't difficult to get enough protein in your diet. One chicken leg
alone will provide you with about 30 grams of protein. One salmon
fillet has about 40 grams of protein, a cup of oatmeal has six grams
of protein, and a cup of asparagus even has two grams of protein.
Since most people get enough protein from their diet, protein
deficiency is rare in developed countries. In underdeveloped
countries, protein deficiency is more common. Severe protein
deficiency is called kwashiorkor. Children with kwashiorkor tend to
have very thin arms and legs and large, distended bellies. Lack of
protein can cause growth failure, loss of muscle mass, a depressed
immune system, lung problems, heart problems, and death.
This Week's Assignment
This week I want you to pay attention to the types of protein you eat
every day. You will learn about choosing healthy protein sources next
week, so right now I want you to keep track of the types of meat,
nuts, seeds, legumes, eggs, dairy, cheeses, fish and seafood you eat.
Make note of how they are prepared and how much you eat every
day.