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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 Determined by AA sequence Specificity of a protein’s function Diversity of protein functions 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 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 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 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 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 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? 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) 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 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 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, sat’d fat, salt cooking methods junk foods, convenience foods 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, sat’d fats cheese & eggs 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 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 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 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: 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)
