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Lecture Presentation Outline
I.
Image versus Reality
 Instructor Resources: Unit 15 Nutrition Scoreboard transparency master; Unit 15 PowerPoint
presentation on Multimedia Manager
A. Term protein is derived from the Greek word protos for “first”
1. Derivation indicates importance of this substance
2. Essential structural component of all life, protein involved in most biological process in the
body
B. A very positive image
1. People know protein is important
2. Nearly all in U.S. get enough protein
3. Most consume more than needed
4. Intakes exceed RDA for almost all
5. 15% of total calories in U.S. adult diet supplied by protein
C. High Protein Intakes
1. Generally accompanied by high-fat and low-fiber intakes
2. Foods high in protein (hamburger, cheese, nuts, eggs) are high in fat and contain little or no
fiber
3. Lean meats provide a large part of their total calories as fat
II. Functions of Protein
A. Proteins perform four major functions
1. Integral structural component of skeletal muscle, bone, connective tissues, organs, red blood
cells and hemoglobin, hair, and fingernails
 Instructor Resources: transparency #43: Red Blood Cells Enmeshed in Fibrin
2.
3.
Basic substance that makes up digestive and other enzymes in the human body
Major component of hormones such as insulin
 Instructor Resources: transparency #44: Structure of Insulin
4. Protein also serves as an energy source
B. Protein Dynamics
1. A 154-pound man has 24 lbs of protein
2. All protein is broken down and re-built
a. Protein turnover uses 9 oz each day
b. We only consume 2-3 oz per day
c. Most protein is recycled from protein substances being ‘turned over’
3. Proteins play key roles in repair of tissues and replacing tissue proteins damaged by illness
or injury
C. Source of Energy
1. Protein serves as a source of energy
2.
Protein contains nitrogen, not stored
a. For energy, amino acids first lose nitrogen
b. Free nitrogen in excess excreted in urine
c. Nitrogen excretion increases need for water
3. Amino acids converted to glucose or fat, then used to form energy
D. Some protein (1%) obtained from liver and blood used to cover deficits in protein intake
III. Amino Acids
A. The “building blocks” of protein are amino acids
1. Protein in food is broken down by digestive enzymes and absorbed into the bloodstream as
amino acids
2. 20 common amino acids form proteins when linked together
3. Protein in the body is a unique combination of amino acids linked together in chains
4. DNA is genetic material that directs protein synthesis and organizes amino acids into chains
B. Characteristics
1. Chains of amino acids fold up into a complex shape
2. Some proteins are made of a few amino acids, others contain hundreds
3. Specific amino acids 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
C. Essential and Nonessential Amino Acids
1. Nine of the 20 common amino acids are considered essential
2. 11 are nonessential
3. All 20 amino acids required to build and maintain protein tissues
4. Body cannot produce (or produce enough) essential amino acids, so they must be provided
by the diet
5. Food proteins contain essential and nonessential amino acids
D. Proteins Differ in Quality
 Instructor Resources: Activity 15-1: Protein Quality and Protein Quantity
1.
2.
3.
4.
Value of proteins varies depending on their essential amino acids
How proteins support tissue construction is protein “quality”
a. High quality have essential amino acids to support tissue needs
b. If essential amino acids are missing, proteins are not formed
c. When required level of essential amino acid is lacking, remaining amino acids are used
for energy
Amino acids are not stored in the body, so we need essential amino acids daily
a. We need foods that provide enough of all essential amino acids every day
Complete Proteins
a. Food sources of high-quality protein are called complete proteins
b. Complete proteins include those found in animal products
c. Incomplete proteins are deficient in one or more essential amino acids
d. Plant proteins are “incomplete”
e. Vegetarians “complement” essential amino acid composition of plant protein by
combining them to form a “complete” source of protein
 Instructor Resources: transparency #46: Protein Complementation
IV. Amino Acid Supplements
A. Amino acids are natural, so people think they’re harmless
B. But high intakes of amino acids can harm health
1. High amounts disrupt protein synthesis by causing a surplus of some amino acids and a
deficit of others
C. Dangers of amino acid supplements:
1. Cause loss of appetite, diarrhea, and gastrointestinal upsets
2. Increase the workload of the liver and kidneys and the likelihood of dehydration
D. The safety of amino acid supplements questioned when something went wrong
E. Tryptophan Supplements
1. Supplements of the amino acid tryptophan caused serious illness
a. People developed painful muscles and joints, weakness, fever, cough, a rash, and
swelling
b. Disease was diagnosed as eosinophilia-myalgia syndrome (EMS)
2. The outbreak was related to tryptophan supplement use
3. People were urged to stop taking the supplements
4. 1500 cases of EMS were reported, 37 people died
5. Many who developed EMS still have the disease
6. Contaminants and tryptophan itself were related to EMS
F. Melatonin
1. Melatonin was marketed after tryptophan supplements banned as a cure for jet lag and a
way to help your body switch to a night shift
2. Studies were inconclusive, but 1 mg per day may improve sleep in adults lacking brain
melatonin
3. Not effective against jet lag or the switch to night shifts
4. Low doses of melatonin (1 milligram per day) do not appear harmful, but safety is still
unclear
5. There is little oversight of the purity or dose levels of melatonin in supplements
G. Build Muscle?
1. Amino acids and protein powders do not cause muscles to grow
2. No amino acids are delivered directly to our muscles and cause muscles to enlarge
3. Only exercise and a good diet build muscles
4. Most athletes get more than enough protein from their usual diet
V. Food as a Source of Protein
A. The average intake in the U.S. is 75 grams per day
1. RDA is 56 grams for men and 46 grams for women
2. 70% comes from meats, milk, and other animal products
B. Dried beans and grains are good sources
C. Most protein provides vitamins and minerals as well
1. Beef and pork are good sources of iron
a. Lean cooked sirloin steak is 29% protein, 30% fat, and 62% water
b. Lean pork is 29% protein, 9% fat, and 61% water
VI. Too Little Protein
A. Protein deficiency occurs alone or with deficiency of calories and other nutrients
1. Protein foods contain nutrients (iron, zinc, vitamin B 12, niacin), protein deficiency is with
others
B. Protein not important source of energy, but body protein can provide energy during starvation
1. Body will take protein from liver, intestines, heart, muscles, other organs and tissues
2. Loss of 30% of body protein yields reduced body strength for breathing, susceptibility to
infection, abnormal organ functions, and death
C. Kwashiorkor
1. Develops after child is weaned from breast milk
2. Protein-deficient body cannot maintain normal blood volume, grow, produce digestive
enzymes, fight infections adequately, or maintain existing tissues
3. Children with protein deficiency are apathetic, irritable, small, and highly vulnerable to
infection
D. Marasmus
1. Protein deficiency and lack of calories cause marasmus, or protein-energy malnutrition
2. Frequent where hunger and famine are common
3. Occurs among people with anorexia nervosa, and diseases such as cancer and AIDS
4. Individuals with marasmus look starved
5. They have little body fat
6. Must utilize protein from muscles, liver, and tissues as an energy source
7. Children with marasmus are apathetic, highly susceptible to infection, have dry skin and
brittle hair, and “skin and bones” appearance
8. Use of the fat pads in the cheeks (last fat used for energy during starvation) gives children
with marasmus appearance of an old person
9. Kwashiorkor and marasmus are accompanied by vitamin and mineral deficiencies
10. Conditions are complicated by infection, diarrhea, and dehydration
VII. Too Much Protein?
A. Adults can consume 35% of total calories without ill effects
B. Consumption of 45% of total calories from protein is too high
1. This much protein causes nausea, weakness, and diarrhea; diets very high in protein result in
death after several weeks
2. Disease from excess protein intake termed “rabbit fever”
3. High protein diets implicated in weak bones, kidney stones, cancer, heart disease, and
obesity
C. NAS concluded risk does not increase for 10-35% of total calories from protein
1. Tolerable Upper Intake Level for protein has not been established
2. People are cautioned not to consume high levels of protein from foods or supplements
D. Trends
1. 2/3 of U.S. protein comes from animal products
2. Wealth leads to meat protein increase
3. Increased consumption of fat too
4. Rates of heart disease and some cancers increase
5. Adequate dietary intakes without excess fat have beans and grains mixed with lean meats
and low-fat dairy products