Proteins and Amino Acids in 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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Protein Structure

• Polymer of amino acids
• Amino acid structure
• amino group (N)
• acid group
• side chain

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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 Structure

• Primary Structure
• sequence of amino acids
• Secondary Structure
• helical coil

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Protein Structure

• Tertiary Structure
• folding of coil
• 3-dimensional structure
• Determined by AA sequence
• Specificity of a proteins function
• Diversity 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 Synthesishow 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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Genetic Disorderserrors 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 theyve eaten GM foods
• 58 say they havent

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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 EngineeringFood and Health Issues

• Traditional animal and plant breeding
• Alteration of genetic material with tools of
  biotechnology
• Advantages
• speed
• more specific, less random
• interspecies gene transfer

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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

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Benefits of Genetically Engineered Foods

• Reduce erosion of topsoil due to tilling
• tilling for weed control
• Monsantos Roundup (glyphosate)
• inhibits plants 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 FoodsEnvironmental
Concerns

• 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?

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Genetically Engineered FoodsHealth
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 Functions

• Enzymes related proteins
• Catalysts
• Membrane transporters
• Cell receptors

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Transport Proteinssodium pumps
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Protein Functions

• Structural Proteins
• Muscle fiber proteins
• Connective proteins

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Protein Functions

• Hormones
• Protein Hormones
• Insulin
• Glucagon
• Amino Acid Derived Hormones
• serotonin
• adrenaline

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Protein Functions

• Antibodies Immune System
• impaired immune system with protein deficiency
• Fluid Balance
• albumin
• edema

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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

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Protein and Nutrition

• Daily protein needs
• Quantity of protein
• Quality of protein
• Protein Quality
• How well a protein meets the bodys need for
  health, growth, etc
• Digestibility
• Amino acid composition
• Essential Amino Acids composition

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Protein Quality

• Measures of protein quality
• Biological Value (BV)
• Measures body retention of food protein
• BV100 gt 100 of food protein retained
• Protein Efficiency Ratio (PER)
• Measures ability of protein to support growth
• g growth/g protein fed
• PER3 gt 3g growth per g or protein fed

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Protein Quality BV
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Protein Quality PER
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Protein Quality

• Vegetarian 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
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Hummus (garbanzo beans) and Pita Bread (wheat)
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Peanut butter (legume) sandwich (wheat)
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Vegetarian DietsWhy become a vegetarian?

• Health benefits
• Environmental concerns about meat based diets
• Animal welfare/ethical considerations
• Economic reasons
• World hunger issues
• Religious beliefs

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Vegetarian DietsPotential 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 DietsConsumer 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. 78S626-632 (2003)

• Continuing Survey of Food Intake by Individual
  (CSFII) 1994-1996
• gt13,000 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 Types

• Non-red meat vegetarian
• poultry, fish, dairy, eggs OK
• 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, satd fat, salt
• cooking methods
• junk foods, convenience foods

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Vegetarian Diets Types

• Lacto-ovo vegetarian
• Milk eggs OK
• Nutritional Benefits
• Like non-meat vegetarians
• Nutritional Concerns
• No special nutritional problems
• May be high in fats, satd fats
• cheese eggs

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Vegetarian Diets Types

• Strict Vegetarian Vegan
• no animal foods
• 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

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Protein Deficiency

• Protein - Energy Malnutrition
• gt 500 million children with PEM
• 33,000 die per day with PEM
• Two major forms of PEM
• Kwashiorkor
• Marasmus

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Protein Deficiency

• 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

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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

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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

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Athletes Protein Needs ?

• Most sport nutritionists recommend
• 1.0 to 1.5 g protein/kg BW
• RDA 0.8 gP/kg BW
• Example of athletes 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 15Pro 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)