Proteins and Amino Acids in Nutrition Dr. David L. Gee FCSN 245 Basic Nutrition.
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Proteins and Amino Acids in Nutrition
Dr. David L. Gee
FCSN 245
Basic Nutrition
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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
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©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
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Protein Structure
Polymer of amino acidsAmino acid structure
–amino group (N)
–acid group
–side chain
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©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
![Page 6: Proteins and Amino Acids in Nutrition Dr. David L. Gee FCSN 245 Basic Nutrition.](https://reader036.fdocuments.in/reader036/viewer/2022062320/56649d6c5503460f94a4bab3/html5/thumbnails/6.jpg)
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
![Page 7: Proteins and Amino Acids in Nutrition Dr. David L. Gee FCSN 245 Basic Nutrition.](https://reader036.fdocuments.in/reader036/viewer/2022062320/56649d6c5503460f94a4bab3/html5/thumbnails/7.jpg)
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
![Page 8: Proteins and Amino Acids in Nutrition Dr. David L. Gee FCSN 245 Basic Nutrition.](https://reader036.fdocuments.in/reader036/viewer/2022062320/56649d6c5503460f94a4bab3/html5/thumbnails/8.jpg)
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
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Protein StructurePrimary Structure
–sequence of amino acidsSecondary Structure
–helical coil
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Protein StructureTertiary Structure
– folding of coil
– 3-dimensional structureDetermined by AA sequence Specificity of a protein’s
functionDiversity of protein functions
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Other Amino Acid Facts
9 “Essential” amino acids– Amino acids that cannot be made and must be
consumed in the diet (dietary essential) peptide bonds link amino acids together proteins typically contain a few hundred
amino acids– infinite combinations of amino acids– tremendous diversity of protein types
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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
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©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
![Page 14: Proteins and Amino Acids in Nutrition Dr. David L. Gee FCSN 245 Basic Nutrition.](https://reader036.fdocuments.in/reader036/viewer/2022062320/56649d6c5503460f94a4bab3/html5/thumbnails/14.jpg)
©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.
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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 ???
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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
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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
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Genetic Engineering:Food and Health Issues
Traditional animal and plant breedingAlteration of genetic material with tools
of biotechnologyAdvantages:
– speed– more specific, less random– interspecies gene transfer
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Benefits of Genetically Engineered Foods
Reduce use of pesticidesBacillus 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
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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)
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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
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Genetically Engineered Foods:
Environmental Concerns Pesticide resistant insectsUnintentional 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?
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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
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Protein FunctionsEnzymes & 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.
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Transport Proteinssodium pumps
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Protein FunctionsStructural Proteins
–Muscle fiber proteins
–Connective proteins
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Protein FunctionsHormonesProtein Hormones
– Insulin
– GlucagonAmino Acid Derived Hormones
– serotonin
– adrenaline
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Protein FunctionsAntibodies & Immune System
– impaired immune system with protein deficiency
Fluid Balance– albumin– edema
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Protein FunctionsAcid-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
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Protein and NutritionDaily 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
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Protein QualityMeasures of protein qualityBiological 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
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Protein Quality: BV
0102030405060708090100
Egg
Milk
Beef
Soy
Peas
Rice
Wheat
Lentils
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Protein Quality: PER
0
0.5
1
1.5
2
2.5
3
3.5
4
Egg
Milk
Beef
Soy
Peas
Rice
Wheat
Lentils
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Protein QualityVegetarian Diets
– Is there a protein problem? Plant proteins are “Incomplete proteins”Complementary Proteins
– Example: Mexican Food Tortilla: low lysine, hi methionine Beans: low in methionine, hi lysine
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Tortillas & Rice with Refried Beans
© 2002 Wadsworth Publishing / Thomson Learning™
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Hummus (garbanzo beans) and Pita Bread (wheat)
© 2002 Wadsworth Publishing / Thomson Learning™
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Peanut butter (legume) sandwich (wheat)© 2002 Wadsworth Publishing / Thomson Learning™
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Vegetarian Diets:Why become a vegetarian?
Health benefitsEnvironmental concerns about meat based
dietsAnimal welfare/ethical considerationsEconomic reasonsWorld hunger issuesReligious beliefs
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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
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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
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“What do vegetarians in the United States eat?”
Am J Clin Nutr. 78S:626-632 (2003)
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
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“What do vegetarians in the United States eat?”
Characteristics of Self-defined Vegetarians
Vegetarians were thinner– BMI: 23 vs 26
Consumed more CHO– 57% vs 50%
Less fat and saturated fat– 27% vs 33% and 9% vs 11%
More vitamin A, carotene, vitamin E, vitamin C, folate, dietary fiber and less cholesterol
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Vegetarian Diets: TypesNon-red meat vegetarian
– poultry, fish, dairy, eggs OKNutritional Benefits
– Less fat, saturated fat, cholesterolNutritional 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
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Vegetarian Diets: TypesLacto-ovo vegetarian
– Milk & eggs OKNutritional Benefits
– Like non-meat vegetarians
Nutritional Concerns– No special nutritional problems– May be high in fats, sat’d fats
cheese & eggs
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Vegetarian Diets: TypesStrict Vegetarian: Vegan
– no animal foodsNutritional Benefits
– Low fats, high fiber, plant-basedNutritional 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
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Protein DeficiencyProtein - Energy Malnutrition
– > 500 million children with PEM– 33,000 die per day with PEM
Two major forms of PEM–Kwashiorkor
–Marasmus
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Protein DeficiencyKwashiorkor
– 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
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Protein DeficiencyMarasmusBoth Protein and Calories
low– inadequate food intake
Symptoms– wasting of lean and fat tissue– weak, anemic, low metabolism– death due to secondary
infections
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Protein Needs RDA = 0.8g Pro/kg BW
–Or ~ 15% of caloriesM = 55 gP/d F = 45 gP/dSafety factor accounts for:
– individual differences– varied protein quality– average requirement 0.5-0.6gP/kg
Typical Intake: 65 - 110 gP/d
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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 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
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For maximal muscle gain: Adequate protein
– 1.2 – 1.5 gPRO/kg BW 175 lbs = 80kg = 96-120gP/day If 3000 Cal diet = 13-16% of Calories
Adequate energy, especially Carbs– 6-7g CHO/kg BW
175 lbs = 480 –560 g CHO If 3000 Cal diet = 64% - 75%
Proper cellular hormonal balance– Genetics– Weight training– Cheating (anabolic steroids, androstenedione (prohormone)