Download Proteins and Amino Acids

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Nutrition Scoreboard
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Proteins and
Amino Acids
1 The primary function of protein is to provide energy.
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3 High-protein diets enhance muscle development in
individuals who work out a lot.
Answers on next page
2 “Nonessential amino acids” are not required for normal body processes. Only “essential amino acids” are.
• Proteins are made of amino
acids. Some amino acids are
“essential” (required in the
diet), and some are
“nonessential” (not a
required part of diets).
• Although protein can be
used for energy, its major
functions in the body
involve the construction,
maintenance, and repair of
protein tissues.
• Protein tissue construc-
tion in the body proceeds
only when all nine essential amino acids are
available.
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Answers to Nutrition Scoreboard
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KEY CONCEPTS AND FACTS
1 Energy is a function of protein, but it’s not the
primary one.
✔
2 “Nonessential amino acids” are required by the body,
but they are not required components of our diet.
(Yes, it is confusing.)
✔
3 Muscles contain protein, but you can’t increase
muscle mass by consuming a high-protein diet—
whether you’re a couch potato or a nationally
ranked athlete.
✔
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[
• Appropriate combinations
of plant foods can supply
sufficient quantities of all
the essential amino acids.
Protein’s Image versus Reality
protein
Chemical substance in foods
made up of chains of amino
acids.
Illustration 15.1
The protein perception.
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Protein
The term protein is derived from the Greek word protos, meaning “first.” The derivation indicates the importance ascribed to this substance when it was first recognized. An essential structural component of all living matter, protein is involved in
almost every biological process in the human body. Protein has a very positive image
(Illustration 15.1). It’s so positive that you don’t have to talk about the importance
of protein—people are already convinced of it.
Rich or poor, nearly all people in the United States get enough protein in their
diets. Actually, most people consume more protein than they need. Average intakes
of protein exceed the Recommended Dietary Allowance (RDA) level for all age and
sex groups. Approximately 15% of total calories in the average U.S. adult diet are
supplied by protein.
High-protein intakes are generally accompanied by high-fat and low-fiber
intakes. That’s because foods high in protein such as hamburger, cheese, nuts, and
eggs are high in fat and contain little or no fiber. Even lean meats provide a considerable proportion of their total calories as fat (Illustration 15.2).
Functions of Protein
Other
nutrients
Proteins perform four major functions in the body (Table 15.1). They are an integral structural component of skeletal muscle, bone, connective tissues (skin, collagen, and cartilage), organs (such as the heart, liver, and kidneys), red blood cells and
hemoglobin, hair, and fingernails. Proteins are the basic substance that make up
digestive enzymes and the thousands of other enzymes in the human body, and they
are a major component of hormones such as insulin. All protein-containing structures and tissues in the body require ongoing maintenance in the form of renewal of
their content of protein. Tissue maintenance and the repair of organs and tissues
damaged due to illness or injury are functions of different types of protein. Finally,
protein serves as an energy source.1
The body of a 154-pound man contains approximately 24 pounds of protein.
Nearly half of the protein is found in muscle, while the rest is present in the skin,
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Felicia Martinez/PhotoEdit
Tony Freeman/PhotoEdit
Tony Freeman/PhotoEdit
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Tony Freeman/PhotoEdit
(i) Pork loin roast: 36%
Felicia Martinez/PhotoEdit
(g) Top round: 25%
Richard Anderson
(j) Pork tenderloin: 28%
(d) Round tip: 34%
(h) Pork chop, lean: 48%
Richard Anderson
(f) Eye of round: 26%
Felicia Martinez/PhotoEdit
Felicia Martinez/PhotoEdit
(e) Sirloin: 33%
(c) Top loin: 41%
Felicia Martinez/PhotoEdit
(b) Tenderloin: 43%
Felicia Martinez/PhotoEdit
Felicia Martinez/PhotoEdit
(a) Hamburger (90% lean): 45%
(k) Chicken thigh, no skin: 47%
(l) Baked chicken breast, no
skin: 19%
Illustration 15.2
The fat content of 3-ounce portions of “lean” meats. The percentage of calories from fat is indicated for each portion. (A 3-ounce
portion of meat is about the size of a deck of cards.) Each portion of meat provides approximately 21 grams of protein.
connective tissue,
organs, and
hemoglobin
2. Serves as the basic
component of
enzymes and
hormones
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3. Maintains and repairs
protein-containing
tissues
4. Serves as an energy
source
Index Stock
collagen, blood, enzymes, and antibodies; organs such as the heart, liver, and
intestines; and other body parts. All protein in the body is continually being
turned over, or broken down and rebuilt. This process helps maintain protein tissues in optimal condition so they continue to function normally. The process of
protein turnover utilizes roughly 9 ounces of protein each day. Yet, we consume
only 2–3 ounces of protein daily. Most of the protein
used for maintenance is recycled from protein tissues
TABLE 15.1
and substances being turned over. Proteins play key
roles in the repair of body tissues by serving as subFUNCTIONS OF PROTEIN.
stances such as fibrin that helps blood clot (Illustration
1. Serves as a structural
15.3) and by replacing tissue proteins damaged by illmaterial in muscles,
ness or injury.2
antibodies
Blood proteins that help the
body fight particular diseases.
They help the body develop an
immunity, or resistance, to
many diseases.
Illustration 15.3
Red blood cells enmeshed in
fibrin in a color-enhanced
microphotograph.
Red blood cells and fibrin
(which helps stop bleeding by
causing blood to clot) are
made primarily from protein.
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Protein serves as a source of energy in healthy people, but not
nearly to the extent that carbohydrates and fats do. Protein is unlike
carbohydrate and fat in that it contains nitrogen and does not have a
storage form in the body. In order to use protein for energy, amino
acids that make up proteins must first be stripped of their nitrogen.
The free nitrogen can be used as a component of protein formation
within the body; or, if present in excess, it is excreted in urine. Excretion of nitrogen requires water, so high intake of protein increases
water need. Amino acids missing their nitrogen component are converted to glucose or fat that then can be used to form energy. A small
amount of protein (1%) can be obtained from the liver and blood and
used to cover occasional deficits in protein intake.3
Amino Acids
The “building blocks” of protein are amino acids (Illustration 15.4).
Protein consumed in food is broken down by digestive enzymes and absorbed into
the bloodstream as amino acids. There are 20 common amino acids (Table 15.2) that
form proteins when linked together. Every protein in the body is composed of a
unique combination of amino acids linked together in chains (Illustration 15.5). The
organization of amino acids into the chains is orchestrated by DNA, the genetic material within each cell that directs protein synthesis. Once formed, the chains of amino
acids may fold up into a complex shape. Some proteins are made of only a few amino
acids, while other proteins contain hundreds. Whatever the number of amino acids,
the specific amino acids involved and their arrangement determine whether the protein is an enzyme, a component of red blood cells, a muscle fiber, or another tissue
made from protein. Nine of the 20 common amino acids are considered essential,
and 11 are nonessential. Despite the labels, all 20 amino acids are required to build
and maintain protein tissues. The essential amino acids are called “essential” because
the body cannot produce them, or produce enough of them, so they must be provided
by the diet. Proteins in foods contain both essential and nonessential amino acids.
Illustration 15.4
Source: © 2001 by Sidney Harris.
DNA (deoxyribonucleic
acid)
Genetic material contained in
cells that initiates and directs
the production of proteins in
the body.
essential amino acids
Amino acids that cannot be
synthesized in adequate
amounts by humans and
therefore must be obtained
from the diet. They are sometimes referred to as “indispensable amino acids.”
Proteins Differ in Quality
nonessential amino acids
Amino acids that can be readily produced by humans from
components of the diet. Also
referred to as “dispensable
amino acids.”
The ability of proteins to support protein tissue construction in the body varies
depending on their content of essential amino acids. How well dietary proteins support protein tissue construction is captured by tests of the protein’s “quality.”
Glycine
Valine
Phenylalanine
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Isoleucine
Glutamine
Histidine
Asparagine
Cysteine
Valine
Glutamine
Cysteine
Glutamic acid
Alanine
Cysteine
Serine
Histidine
Glycine
Valine
Serine
Valine
Glutamic acid
Leucine
Leucine
Leucine
Alanine
Serine
Tyrosine
Cysteine
Glutamine
Leucine
Valine
Tyrosine
Asparagine
Glycine
Cysteine
Leucine
Tyrosine
Glutamic acid
Cysteine
Asparagine
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Leucine
Arginine
Glutamic acid
Glycine
Phenylalanine
Tyrosine
Phenylalanine
Threonine
Lysine
Proline
Alanine
Illustration 15.5
Amino acid chains in the
protein insulin (shown at
right) and the structure
of insulin (shown above).
Tryptophan
Valine
Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine
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Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
NONESSENTIAL
Proteins of high quality contain all the essential amino acids in the amounts
needed to support protein tissue formation by the body. If any of the essential amino
acids are missing in the diet, proteins are not formed—even those proteins that could
be produced from available amino acids. Shutting off all protein formation for want
of an amino acid or two may appear inefficient; but if the body did not cease all protein formation, cells would end up with an imbalanced assortment of proteins. This
would seriously affect cell functions. When the required level of an essential amino
acid is lacking, the remaining amino acids are primarily used for energy.
Amino acids cannot be stored very long in the body, so we need a fresh supply
of essential amino acids daily. This means we need to consume foods that provide a
sufficient amount of all essential amino acids every day.
Complete Proteins] Food sources of high-quality protein (meaning they contain
complete proteins
Proteins that contain all of
the essential amino acids in
amounts needed to support
growth and tissue maintenance.
incomplete proteins
Proteins that are deficient in
one or more essential amino
acids.
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Vegetarian Diets] Diets consisting only of
plant foods can provide an adequate amount
of complete proteins. The key to success is
eating a variety of complementary sources of
protein each day. Vegetarian diets have been
practiced for centuries by some religious and
cultural groups, bearing testimony to their
general adequacy and safety. (Unit 16 on
vegetarian diets expands on this topic.)
David Young-Wolff/PhotoEdit
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all the essential amino acids in the amount needed to support protein formation)
are called complete proteins. Proteins in this category include those found in animal products such as meat, milk, and eggs
(Illustration 15.6). Incomplete proteins are
deficient in one or more essential amino
acids. Proteins in plants are “incomplete,”
although soybeans are considered a complete source of protein for adults.4 (Soybeans may not meet the essential amino acid
requirements of young infants.) You can
“complement” the essential amino acid
composition of plant sources of protein by
combining them to form a “complete”
source of protein. Illustration 15.7 shows a
few plant combinations that produce complete proteins.
Illustration 15.6
Animal sources of protein
supply “complete proteins.”
Each food shown is a source of
complete protein.
Illustration 15.7
Each of these combinations of plant foods is also a source of complete
protein. Shown are mixed vegetables, tofu, and brown rice; succotash (lima
beans and corn), and rice and black beans.
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ESSENTIAL
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ESSENTIAL AND NONESSENTIAL AMINO ACIDS.
Richard Anderson
TABLE 15.2
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Amino Acid Supplements
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Illustration 15.8
A wide array of amino acid
supplements are available
over the counter, but the
safety of these supplements
is unknown.
Richard Anderson
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Because amino acids occur naturally in foods, people often assume they are harmless,
no matter how much is taken (Illustration 15.8). Researchers have known for
decades, however, that high intakes of individual amino acids can harm health. High
amounts may disrupt normal protein production by overwhelming cells with a
surplus of some amino acids and a relative deficit of others. Amino acid supplements
have been known to cause loss of appetite, diarrhea, and other gastrointestinal
upsets.5 They increase the workload of the liver and kidneys and the likelihood of
dehydration.6 The safety of amino acid supplements began to gain the public’s attention in 1989 when something went wrong.
The Tryptophan Supplement Scare] Nature’s original sleeping pill? Safe as a
cup of warm milk? Supplements of the amino acid tryptophan (pronounced “trip-toefan”) turned into heartbreaking stories of a serious illness that terrified many people.
Late in the summer of 1989, people from coast to coast developed a mysterious
illness characterized by painful muscles and joints, weakness, fever, cough, a rash,
and swelling. Some people who had the disease described the muscle pain as “like
having a charley horse” in every muscle. Diagnosing the cause of the symptoms
turned out to be difficult. Within a few months, however, the disease was diagnosed
as eosinophilia-myalgia syndrome (EMS). It has no cure. The outbreak was quickly
related to tryptophan supplement use when researchers confirmed that 98% of the
patients with EMS used tryptophan.7 In March 1990, tryptophan was taken off the
market, and people were urged to stop taking the supplements. By late 1990, over
1500 cases of EMS had been reported and at least 37 people died from the disease.
Over 15 years later, many people who developed EMS from the supplement still
have the disease. Contaminants in certain batches of the supplement and tryptophan
itself have been related to the development of EMS.8 Although history now, the
tryptophan scare taught us an important lesson about the potential hazards of
amino acid supplements.
Melatonin: The Tryptophan Replacement?] A derivative of tryptophan, the
Richard Anderson
Illustration 15.9
Tryptophan supplements were
banned in the United States
on April 23, 1990, a month
after their recall.
A close chemical relative,
melatonin, is available. Other
derivatives of tryptophan are
also available, and safety is a
concern.
hormone melatonin (Illustration 15.9), entered the marketplace shortly after
tryptophan supplements were banned. In addition to promoting drowsiness and
sleep, melatonin has been touted as a cure for jet lag and a way to help your body
switch to a night shift. Studies have produced conflicting results on the ability of
melatonin to facilitate sleep in young adults, but doses of about 1 milligram per
day may improve sleep in older adults lacking normal levels of brain melatonin.
It does not appear to be effective against jet lag or helpful in the switch to night
shifts.9
Low doses of melatonin (1 milligram per day) do not appear to be harmful, but
the safety of melatonin supplements is still unclear. As was the case for tryptophan,
there is little oversight of the purity or dose levels of melatonin in supplements.
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Can Amino Acid Supplements and Protein Powders Build Muscle?] You
can’t just consume amino acids or protein powders and watch your muscles grow
(no matter how convincing the ads that sell such products are).10 If that happened,
everyone who wanted a rippled stomach and bulging triceps could have them. No
amino acids or protein powders are delivered directly to our muscles and cause
muscles to enlarge. Only exercise and a good diet build muscles (Illustration 15.10).
Most athletes get more than enough protein from their usual diet to support their
need for it—which is not extraordinarily high.11
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The average intake of protein in the United States is 75 grams per day, exceeding the
RDA for men of 56 grams and that for women of 46 grams.12 Approximately 70%
of the protein consumed by Americans comes from meats, milk, and other animal
products.8 Dried beans and grains are not as well known for their protein, but are
nevertheless good sources (Table 15.3). Plant sources of protein are generally low in
fat, making them a wise choice for consumers who are trying to limit their intake of
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Food as a Source of Protein
TABLE 15.3
FOOD SOURCES OF PROTEIN.
The adult RDA is 46 grams for women aged 19 to 24 years and 58 grams for men aged 19 to
24 years.
FOOD
Animal products
Tuna (water packed)
Shrimp
Cottage cheese (low-fat)
Beef steak (lean)
Chicken (no skin)
Pork chop (lean)
Beef roast (lean)
Skim milk
Fish (haddock)
Leg of lamb
Yogurt (low-fat)
Hamburger (lean)
Egg
Swiss cheese
Sausage (pork links)
2% milk
Cheddar cheese
Whole milk
Dried beans and nuts
Tofu
Soybeans (cooked)
Split peas (cooked)
Lima beans (cooked)
Dried beans (cooked)
Peanuts
Peanut butter
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Grains
Corn
Egg noodles (cooked)
Oatmeal (cooked)
Whole-wheat bread
Macaroni (cooked)
White bread
White rice (cooked)
Brown rice (cooked)
AMOUNT
GRAMS
PROTEIN CONTENT
PERCENTAGE OF TOTAL CALORIES
3 oz
3 oz
1
⁄2 cup
3 oz
3 oz
3 oz
3 oz
1 cup
3 oz
3 oz
1 cup
3 oz
1 medium
1 oz
3 oz
1 cup
1 oz
1 cup
24
11
14
26
24
20
23
9
19
22
13
24
6
8
17
8
7
8
89%
84
69
60
60
59
45
40
38
37
34
34
32
30
28
26
25
23
1
14
10
5
6
8
9
4
38
33
31
27
26
17
17
3
4
3
2
3
2
2
2
29
25
15
15
13
13
11
10
⁄2 cup
⁄2 cup
1
⁄2 cup
1
⁄2 cup
1
⁄2 cup
1
⁄4 cup
1 tbs
1
1
⁄2 cup
⁄2 cup
1
⁄2 cup
1 slice
1
⁄2 cup
1 slice
1
⁄2 cup
1
⁄2 cup
1
Illustration 15.10
No amount of protein
powders or amino acid
supplements will build
muscles like these. Exercise
and a good diet are needed to
build muscles.
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What Happens When a Diet Contains Too Little Protein?
3.4
Round steak
(lean)
3.1
Hamburger
(lean)
3.0
Shrimp
2.6
1.6
Baked chicken
(no skin)
1.4
Lamb (lean)
1.3
kwashiorkor (kwa-she-orkor)
A deficiency disease primarily
caused by a lack of complete
protein in the diet. It usually
occurs after children are taken
off breast milk and given solid
foods containing low-quality
protein.
Dr. Robert S. Goodhard, M.D.
Pork chop
(lean)
Protein deficiency can occur by itself or in combination with a deficiency of calories
and nutrients. Because food sources of protein generally contain essential nutrients
such as iron, zinc, vitamin B12, and niacin, diets that produce protein deficiency usually cause a variety of other deficiencies, too. Protein does not generally serve as an
important source of energy, but body protein will be used as a major energy source
during starvation. To meet the need for energy, the body will extract protein from
the liver, intestines, heart, muscles, and other organs and tissues. Loss of more than
about 30% of body protein results in reduced body strength for breathing, susceptibility to infection, abnormal organ functions, and death.13
Kwashiorkor is a severe form of protein deficiency in children. It usually develops
after a child has been weaned from breast milk and given high-carbohydrate, lowprotein foods such as cassava or a watery gruel made from oats, rice, or corn. A
protein-deficient body cannot grow, maintain a normal level of blood volume, produce digestive enzymes, fight infections adequately, or maintain existing tissues in
proper working order. As seen in Illustration 15.11, children with kwashiorkor may
look fat due to edema (swelling), but they are actually very skinny. Children with protein deficiency are apathetic, irritable, small, and highly vulnerable to infection.
Protein deficiency may be accompanied by a lack of calories. In this case, a condition called marasmus, or protein-energy
malnutrition, exists. Unfortunately, this
condition is all too frequent in areas of the
Dr. Robert S. Goodhard, M.D.
MEAT
IRON
CONTENT
(MG)
Tuna
fat. Nearly all food sources of protein provide an assortment of vitamins and minerals as well. Beef and pork are particularly good sources of iron, a mineral often
lacking in the diets of women (Table 15.4).
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IRON CONTENT IN A
3-OUNCE SERVING OF
VARIOUS MEATS.
The RDA for women aged
19 to 24 years is 15 milligrams. The RDA for men
aged 19 to 24 years is 10
milligrams.
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TABLE 15.4
edema
Swelling due to an accumulation of fluid in body tissues.
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marasmus
A condition of severe body
wasting due to deficiencies of
both protein and calories. Also
called protein-energy malnutrition and protein-calorie
malnutrition.
Illustration 15.11
Children suffering from a severe form of
protein deficiency called kwashiorkor
experience swelling in the arms, legs, and
stomach area. The swelling hides the devastating wasting that is taking place within
their bodies. The child at left has the characteristic “moon face” (edema), swollen belly,
and patchy dermatitis (from zinc deficiency)
often seen with kwashiorkor. At right, the
same child after nutritional therapy.
Illustration 15.12
Individuals with marasmus look as starved as
they are. People with this condition lack both
protein and calories. The child at left is suffering from the extreme emaciation of marasmus.
At right is the same child after nutritional
therapy.
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You’ve got a nutrition exam coming up,
so you and your classmate Scenario have
gotten together to study. You get into a
discussion about food sources of protein
that goes like this:
Scenario:
Lean meats are the best
source. They’re pure
protein!
Who gets the “thumbs up”
?
Answers on next page
world where hunger and famine are common. It is also the type of malnutrition that
occurs among people with severe anorexia nervosa and in certain diseases such as
cancer and AIDS. Individuals with marasmus look starved and wasted (see Illustration 15.12). They have precious little body fat and must utilize protein from muscles,
the liver, and other tissues as an energy source.
In addition to having a skin-and-bones appearance, children with marasmus are
apathetic, highly susceptible to infection, and have dry skin and brittle hair. Use of
the fat pads in the cheeks for energy (which are among the last fat deposits to be used
for energy during starvation) gives children with advanced cases of marasmus the
look of a very old person. Both kwashiorkor and marasmus are generally accompanied by multiple vitamin and mineral deficiencies due to limited food intake. The
conditions are frequently complicated by infection, diarrhea, and dehydration.
How Much Protein Is Too Much?
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Adults can consume a substantial amount of protein—approximately 35% of total
calories—for months at a time without ill effects. This observation is based on studies of the diets of Eskimos, explorers, trappers, and hunters in northern America.
The very high-protein diets would generally contain a good deal of fat in the form
of whale blubber, lard, or fat added to dried meat. Consumption of 45% of total
calories from protein is considered too high. Consumption of this level of protein is
related to nausea, weakness, and diarrhea. Diets very high in protein result in death
after several weeks. The disease resulting from excess protein intake was termed
“rabbit fever” after it occurred in trappers attempting to exist on wild rabbit only.14
High-protein diets have been implicated in the development of weak bones, kidney stones, cancer, heart disease, and obesity. The National Academy of Sciences has
concluded that the risk of such disorders does not appear to be increased among
individuals consuming 10 to 35% of total calories from protein, and on average
adults consume 15%.15
A Tolerable Upper Intake Level (UL) for protein has not been established.
Because information on the effects of high-protein intakes is limited, people are cautioned not to consume high levels of protein from foods or supplements.
Pickles:
Pure protein? Even the
driest, toughest meats
contain more than
protein.
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Pure protein
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REALITY CHECK
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REALITY CHECK
Pure protein
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Some people think muscle and lean meat consist only of protein. They don’t. By weight,
lean cooked sirloin steak is 29% protein, 8%
fat, and 62% water. Lean pork is 29% protein,
9% fat, and 61% water, for example.
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ANSWERS TO
Scenario
Pickles
Trends
In the early 1900s about half of the protein consumed in the United States came
from plant sources and half from animal sources. Now, approximately two-thirds
of the protein intake comes from animal products.16 As countries develop economically, the proportion of dietary protein obtained from meats tends to increase. The
increased intake of protein from meats is accompanied by an increased consumption
of fat and by elevated rates of some of the “diseases of Western civilization” such as
heart disease and certain cancers. Adequate intakes of protein without excess levels
of fat can easily be obtained from diets that include dried beans, cereals, and other
grains as sources of protein as well as lean meats and low-fat dairy products.
Key Terms
antibodies, page 15-3
essential amino acids, page 15-4
nonessential amino acids, page 15-4
complete proteins, page 15-5
incomplete proteins, page 15-5
protein, page 15-2
DNA (deoxyribonucleic acid),
kwashiorkor (kwa-she-or-kor),
page 15-4
edema, page 15-8
page 15-8
marasmus, page 15-8
www links
www.healthfinder.gov
Search topics related to protein.
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www.nemsn.org
The National EMS Network provides information on symptoms, current issues, and
answers to questions about EMS, tryptophan, and melatonin.
www.iom.edu
Select “Food & Nutrition” to gain access to
Dietary Reference Intake report on
macronutrients and the chapter on Protein.
www.nal.usda.gov/fnic/etext/macronut.html
You will find the topic “protein” listed and
linked to a wealth of information on functions, structures, food sources, and more.
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Nutrition
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LY T Y
± N OF
OT C E
N
FO G A
R GE
SA
LE LEA
OR R N
CL ING
AS
SR
O
My Protein Intake
FOCAL POINT: Determine the amount of protein in your diet yesterday.
For each serving of a food item
you ate yesterday, write the
grams of protein the food contains in the corresponding
blank. For example, a standard
serving of meat is 3 ounces
(about the size of the palm of
your hand or a deck of cards).
Food
Animal products
Milk (whole)
Yogurt
Cottage cheese
Hard cheese
Hamburger (lean)
Beef steak (lean )
Chicken (no skin)
Pork chop (lean)
Fish
Hot dog
Sausage
Plant products
Bread
Rice
Pasta
Cereals
Vegetables
Peanut butter
Nuts
Cooked beans (legumes)
If you had one 3-ounce pork
chop yesterday, write 20 grams
in the corresponding blank. If
you had two 3-ounce pork
chops, write 40 grams. If a protein food you ate yesterday is
not included, choose the item
One Serving
1 c (8 oz)
1 c (8 oz)
1
⁄2 c (4 oz)
1 oz
3 oz
3 oz
3 oz
3 oz
3 oz
1
3 oz
1 slice
⁄2 c (4 oz)
1
⁄2 c (4 oz)
1
⁄2 c (4 oz)
1
⁄2 c (4 oz)
1 tbs
1
⁄4 c (2 oz)
1
⁄2 c (4 oz)
1
Protein in
One Serving
(grams)
on the list closest to it. Then,
total the grams of protein you
ate yesterday from both plant
and animal sources. Finally,
compare your protein intake
with the RDA of 46 grams for
women or 56 grams for men.
Protein You Ate
(grams)
8
13
14
7
24
26
24
20
19
6
17
Subtotal from animal foods:
2
2
3
3
2
4
7
8
Subtotal from plant foods:
Total grams of protein from
plant and animal foods:
Amount above/below RDA:
FO
R
Special note: You can also calculate your protein intake using Wadsworth Diet Analysis Plus software. Input your food
intake for one day. Then go to the Analyses/Reports section to view the total number of grams of protein in your diet.
FEEDBACK can be found at the end of Unit 15.
US
E
7. Centers for Disease Control. Update:
eosinophilia-myalgia syndrome associated with ingestion of L-tryptophan—
United States, as of January 9, 1990.
JAMA 1990;263–633.
aids: reported facts and claims, SCAN’s
Pulse 1999;winter:12–21.
11. Dietary Reference Intakes, Energy, . . .
amino acids.
RE
VI PR
EW O P
ON E R
LY T Y
± N OF
OT C E
N
FO G A
R GE
SA
LE LEA
OR R N
CL ING
AS
SR
O
1. Dietary Reference Intakes. Energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Institute
of Medicine, National Academy of Sciences, Washington, DC: National Academies Press; 2002.
OM
Notes
8. Information paper on 5-hydroxytryptophan and 5-hydroxy-L-tryptophan,
www.nal.usda.gov/fnic/etext/macronut
.html, accessed 7/03.
2. Dietary Reference Intakes, Energy, . . .
amino acids.
3. Matthews DE. Proteins and amino
acids. In: Modern nutrition in health
and disease, 9th edition, Shils ME et al.,
eds. Philadelphia: Lippincott, Williams
& Wilkins, 1998, pp. 11–48.
4. Dietary Reference Intakes, Energy, . . .
amino acids.
5. Dietary Reference Intakes, Energy, . . .
amino acids.
6. High protein intake harms the kidneys.
www.healthfinder.gov/high protein diet,
accessed 9/03.
Nutrition
9. Brzezinski A, Melatonin in humans,
New Engl J Med 1997;336:186–95; and
Arendt J, Jet-lag and shift work, Therapeutic uses of melatonin. J Royal Soc
Med 1999;92:402–5.
10. Lund BC, Perry PJ, Nonsteroid
performance-enhancing agents in
athletic competition: an overview for clinicians, Medscape Pharmacotherapy:
www.medscape.com/Medscape/
pharmacology/journal/2000/v02,n05;
accessed Sept. 25, 2000; and Ergogenic
12. Dietary Reference Intakes, Energy, . . .
amino acids.
13. Matthews, Proteins and amino acids.
14. Dietary Reference Intakes, Energy, . . .
amino acids.
15. Dietary Reference Intakes, Energy, . . .
amino acids.
16. McDowell MA et al. Energy and
macronutrient consumption of persons 2
months and over in the United States:
third national Health and Nutrition
Examination Survey, 1988–91.
Hyattsville, MD: National Center for
Health Statistics, 1994.
UP CLOSE
My Protein Intake
Feedback for Unit 15
FO
R
Compare your subtotals to find out which protein source you prefer, plant or animal. Protein
from animal products is often accompanied by fat. If you are concerned about calories and fat in
your diet, choose plant protein sources more often. And, if you are similar to many Americans,
your intake of protein will exceed the RDA by quite a bit.