Transcript Proteins and Amino Acids in Nutrition

Proteins and Amino
Acids in Nutrition
Dr. David L. Gee
FCSN 245
Basic Nutrition

Biologically:
– proteins are the most important
molecues in the body
“action

molecues”
Nutritionally: (at least in the US)
– proteins are of the least concern for
macronutrients in the diet
protein
deficiency very unusual
excess protein generally not a problem
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Protein Structure
 Polymer
of amino acids
 Amino acid structure
–amino group (N)
–acid group
–side chain
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license.
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Amino Acids




20 different amino acids
– Differ by type of side chain
Water soluble AA
– charged side groups
Can form ionic bonds
– sulfer containing side groups
Can form disulfide bonds
Fat soluble AA
– Fat soluble AA interact/dissolve with each other
These interaction/bonds between AA side chains
cause proteins to form specific shapes
Protein Structure
 Primary
Structure
–sequence of amino acids
 Secondary
Structure
–helical coil
Protein Structure

Tertiary Structure
– folding of coil
– 3-dimensional structure
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Determined by AA sequence
Specificity of a protein’s
function
Diversity of protein functions
Other Amino Acid Facts
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9 “Essential” amino acids
– Amino acids that cannot be made and must be
consumed in the diet (dietary essential)

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peptide bonds link amino acids together
proteins typically contain a few hundred
amino acids
– infinite combinations of amino acids
– tremendous diversity of protein types
Protein Synthesis:
how proteins are made

DNA, genes, chromosomes
– where the information is stored

“Transcription”
– making a copy of the information
– messenger RNA

“Translation”
– reading the information and making the protein
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license.
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
Genetic Disorders:
errors in the stored information

Examples:
– Sickle Cell Anemia
– Cystic Fibrosis
– Familial Hypercholesterolemia
 LDL-receptor

Human Genome Project
– Map the genome
20-25,000
genes in human genome (10/04)
– Fix the genes ???
Have you eaten GM foods?
Are GM foods safe?

2003 survey of US consumers
– Non-partisan Pew Initiative on Food and Biotechnology

48 % opposed to GM foods, 25% in favor
– 2001 58% opposed to GM foods

24% say they’ve eaten GM foods
– 58% say they haven’t
Genetic Modified Crops:
Prevalence

In 2003 (USDA) genetically modified crops accounted for:
– 40% of all corn
– 81% of soybeans
– 73% of cotton

In 2002
– 35% of corn
– 55% of soybeans

Grocery Manufactures of America (2003)
– 70-80% of processed foods contain GMO

USDA approval for
– potatoes, tomatoes, melons, beets
– nicotine free tobacco
Genetic Engineering:
Food and Health Issues
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Traditional animal and plant breeding
Alteration of genetic material with
tools of biotechnology
Advantages:
– speed
– more specific, less random
– interspecies gene transfer
Benefits of Genetically
Engineered Foods

Reduce use of pesticides

Bacillus thuringiensis (Bt)
– “natural” pesticide used by organic
farmers
– Bt produces a protein toxic to insect
larvae

Gene for Bt toxin incorporated into
corn, etc.
– Corn plant produces Bt protein toxin
Benefits of Genetically
Engineered Foods

Reduce erosion of topsoil due to tilling
– tilling for weed control

Monsanto’s “Roundup” (glyphosate)
– inhibits plant’s ability to make tryptophan
– tryptophan is an EAA for humans

Roundup resistant plants (soybeans)
– spliced bacterial gene into plant that is resistant to
effect of Roundup (still able to make tryptophan)
Benefits of Genetically
Engineered Foods

Improved nutritional quality of
plants
– “golden rice”
 rice
with B-carotene gene
– improved protein quality & quantity
– higher in vitamins

Improved sensory properties
– Tomato and strawberry flavor & texture
Genetically Engineered Foods:
Environmental Concerns

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Pesticide resistant insects
Unintentional environmental effects
– monarch butterfly larvae - lab study
– affect beneficial insects (ladybugs)
– development of “superweeds”, “superbugs”

Control of Food Production
– Terminator gene
 GMO
plants with gene to produce sterile seeds
– Biotech firms with too much control?
Genetically Engineered Foods:
Health Issues
(Theoretical problems?)

Lack of long term feeding trials
– animal studies, human studies

Food allergies
– antifreeze protein from fish

Labeling Issue
– Pros: consumer has the right to know
– Cons: unnecessary, no evidence of
environmental/health concerns, will hurt
sales and stymie further development
Protein Functions

Enzymes & related proteins
– Catalysts
– Membrane transporters
– Cell receptors
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license.
Transport Proteins
sodium pumps
Protein Functions
 Structural
Proteins
–Muscle fiber proteins
–Connective proteins
Protein Functions
 Hormones

Protein Hormones
– Insulin
– Glucagon

Amino Acid Derived Hormones
– serotonin
– adrenaline
Protein Functions
 Antibodies
& Immune
System
– impaired immune system with protein
deficiency
 Fluid
Balance
– albumin
– edema
Protein Functions
 Acid-Base
Balance
– buffer
– acidosis & alkalosis
 Energy
& Glucose
– Unlike fats, amino acids can be converted into
glucose (required for CNS/brain function)
starvation
low carbohydrate diets
– body cannibalizes body proteins to make glucose
Protein and Nutrition
 Daily
protein needs
– Quantity of protein
– Quality of protein
 Protein
Quality
– How well a protein meets the body’s need
for health, growth, etc…
Digestibility
Amino
acid composition
– Essential Amino Acids composition
Protein Quality

Measures of protein quality

Biological Value (BV)
– Measures body retention of food protein
– BV=100 => 100% of food protein retained

Protein Efficiency Ratio (PER)
– Measures ability of protein to support growth
– g growth/g protein fed
– PER=3 => 3g growth per g or protein fed
Protein Quality: BV
100
90
80
70
60
50
40
30
20
10
0
Egg
Milk
Beef
Soy
Peas
Rice
Wheat
Lentils
Protein Quality: PER
4
3.5
3
2.5
2
1.5
1
0.5
0
Egg
Milk
Beef
Soy
Peas
Rice
Wheat
Lentils
Protein Quality
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Vegetarian Diets

– Is there a protein problem?
Plant proteins are “Incomplete proteins”
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Complementary Proteins
– Example: Mexican Food
Tortilla:
low lysine, hi methionine
Beans: low in methionine, hi lysine
Tortillas & Rice with Refried
Beans
© 2002 Wadsworth Publishing / Thomson Learning™
Hummus (garbanzo beans) and
Pita Bread (wheat)
© 2002 Wadsworth Publishing / Thomson Learning™
Peanut butter (legume)
sandwich (wheat)
© 2002 Wadsworth Publishing / Thomson Learning™
Vegetarian Diets:
Why become a vegetarian?
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Health benefits
Environmental concerns about meat based
diets
Animal welfare/ethical considerations
Economic reasons
World hunger issues
Religious beliefs
Vegetarian Diets:
Potential Health Benefits

Obesity
– % of obesity lower in vegetarian populations

Cardiovascular Disease
– Risk of CHD 31% lower in vegetarian men and 20%
lower in vegetarian women
– Lower LDL-C, lower HDL-C

Hypertension
– 42% non-veg with hpt, 13% vegetarians

Also lower prevalence for
– Diabetes
– Cancer
Vegetarian Diets:
Consumer Trends - 2000

2.5% of adult Americans are vegetarians
– 4.8 million people
– Slightly less than 1% are vegans

20-25% of adult Americans eat 4 or more
meatless meals weekly
“What do vegetarians in the United
States eat?”
Am J Clin Nutr. 78S:626-632 (2003)
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Continuing Survey of Food Intake by
Individual (CSFII): 1994-1996
– >13,000 subjects
2

day food records
2.5% considered themselves as vegetarian
– 36% of self-defined vegetarians actually
consumed no meat

~4% of total consumed no meat
“What do vegetarians in the United States eat?”
Characteristics of Self-defined
Vegetarians
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Vegetarians were thinner
– BMI: 23 vs 26
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Consumed more CHO
– 57% vs 50%
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Less fat and saturated fat
– 27% vs 33% and 9% vs 11%
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More vitamin A, carotene, vitamin E, vitamin C,
folate, dietary fiber and less cholesterol
Vegetarian Diets: Types
 Non-red
meat vegetarian
– poultry, fish, dairy, eggs OK
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Nutritional Benefits
– Less fat, saturated fat, cholesterol

Nutritional Concerns
– no special nutritional problems
– May not be any better than typical US diet
 may
be high in fat, sat’d fat, salt
cooking methods
 junk foods, convenience foods

Vegetarian Diets: Types
 Lacto-ovo
vegetarian
– Milk & eggs OK
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Nutritional Benefits
– Like non-meat vegetarians
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Nutritional Concerns
– No special nutritional problems
– May be high in fats, sat’d fats
cheese
& eggs
Vegetarian Diets: Types
 Strict
Vegetarian: Vegan
– no animal foods
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Nutritional Benefits
– Low fats, high fiber, plant-based
Nutritional Concerns
– protein quality

probably OK, quantity may be an issue
– calcium

no dairy, plant sources (leafy greens, soy), fortified foods (soy, rice milk)
– iron

no meat, plant sources (leafy greens), cereals
– vitamin B-12

probably OK, cereals & supplements
Protein Deficiency
 Protein
- Energy Malnutrition
– > 500 million children with PEM
– 33,000 die per day with PEM
 Two
major forms of PEM
–Kwashiorkor
–Marasmus
Protein Deficiency
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Kwashiorkor
– Ghana “the evil spirit that infects the first
child when the second child is born”
Protein low, Calories OK
Symptoms
– edema
– enlarged fatty liver
– light colored hair

low tyrosine/melanin
– skin lesions
Protein Deficiency
 Marasmus
 Both Protein and Calories
low
– inadequate food intake

Symptoms
– wasting of lean and fat tissue
– weak, anemic, low metabolism
– death due to secondary
infections
Protein Needs
 RDA =
0.8g Pro/kg BW
–Or ~ 15% of calories
M
= 55 gP/d F = 45 gP/d
 Safety factor accounts for:
– individual differences
– varied protein quality
– average requirement 0.5-0.6gP/kg
 Typical
Intake: 65 - 110 gP/d
Athlete’s Protein Needs ?

Most sport nutritionists recommend
– 1.0 to 1.5 g protein/kg BW
– RDA = 0.8 gP/kg BW

Example of athlete’s protein needs
 175
lb = 80 kg athlete
– 80 kg x 1.5gP/kg =
 120
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
g protein needed per day
So do athletes need to supplement their
diets? Usually not.
3500 Cal/d x 15%Pro = 525 Cal Pro
– 525 Cal P / 4 Cal/gPro =
 131
g pro in normal diet
For maximal muscle gain:
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Adequate protein
– 1.2 – 1.5 gPRO/kg BW
175 lbs = 80kg = 96-120gP/day
 If 3000 Cal diet = 13-16% of Calories

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Adequate energy, especially Carbs
– 6-7g CHO/kg BW
175 lbs = 480 –560 g CHO
 If 3000 Cal diet = 64% - 75%
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Proper cellular hormonal balance
– Genetics
– Weight training
– Cheating (anabolic steroids, androstenedione
(prohormone)