Proteins and Vegetarianism Lecture 5 Units 15, 16

Chemistry n Composition: C H O N (S) n Amino Acids “building blocks” –Amine group (NH 2 ) –Acid group (COOH) –Differ by side group (“R”) n 9 : from food n 11 Nonessential AA: can be made from other AA

Amino Acid, Peptide & Protein Amino acid NH 2 R C COOH Peptide and protein AA 1 -AA 2 -AA 3 -AA AA n

Digestion & Absorption n HCl n Enzymes split long chain of AA for absorption n Blood transports AA to liver & muscle

Functions of Protein n Growth, build & maintenance of tissues n Regulate body processes: Water (fluid) balance--prevent edema Acid-Base (pH) balance--buffers Immune system - antibodies n Energy source--4 calories / gram

Protein Synthesis n DNA code controls : Which AA needed What order AA go on new chain AA 3 AA 1 + AA 2 AA 1 AA 2 AA 1 AA 2 AA 3 n Requires: Calories Essential AA from AA pool Non-essential AA from synthesis or diet

Process of Protein Synthesis DNA  RNA ----  Protein Transcription Translation DNA=deoxyribonucleic acid RNA=ribonucleic acid

Catabolism of Protein n Breakdown of protein to AA n AA converted to fat when excess AA n N from AA is reused for AA synthesis; excess is excreted in urine –May cause loss of Ca in urine –Kidney disease problem

Protein Quality n Complete Protein High quality All essential AA in needed amounts Animal sources n Incomplete Protein Plant sources n 70% of protein from animal sources in US

Complementary Protein n Plant protein (legume) with limiting AA combined with different plant protein (grain) different limiting AA eaten together give complete protein

Plants provide Incomplete Protein n Low in one or more ess. AA n Eat in combo to “complete” the AA balance

Protein Requirements n.8 gm/kg body weight n Protein RDA 46 gm for women 58 gm for men 10-12% kcal from protein n Actual US Intake >80 gm >110 gm ~17% kcal from protein

Food Sources of Proteins n Meat n Fish n Poultry n Eggs Beef & pork rich in iron but high in fat

More Good Protein Sources n Dairy products select low fat (butter not protein) n Legumes n Cereal grains n Seeds n Nuts n Plant sources of protein are low in fat

What about protein for athletes? n Athlete needs 1.26 gm / Kg (~90 gm) n (but typical US male eats >110 gm and female eats >80 gm) n Thus… supplements not needed n What does the body do with the added amino acid? n What builds muscle: exercise and a good diet

Amino Acid Supplement n High intake of a single AA leads to AA imbalance and is harmful n Many AA supplements on market, n Surplus of AA causes diarrhea, loss of appetite, GI upsets n Tryptophan supplements were banned in 1990 n Athletes

Vegetarian Diets n Semi-vegetarian: –lacto vegetarian –ovo vegetarian n Strict vegetarian: –“Vegan” –healthy diets use complementary proteins n Macrobiotic diet: locally grown and whole foods; Yin(“cold”)&yang(“warm”) foods

Vegetarian Diets & Health n Associated with low risk of chronic diseases n May lead to n Vegans: vitamins B 12 and D, Ca, Zn are at risk n Adequately planned vegetarian diets can n The key to achieve healthy diet: variety

Protein deficiency--Marasmus n Chronic food deprivation,diseases n Protein & calories n Impairs brain development & learning n Severe weight loss n Infection, diarrhea

Protein deficiency -- Kwashiorkor n Deficiency in protein but not calories n Children 1-3 years n Some weight loss n Edema n Hair: dry, brittle, changes color (lack of AA to make melanin)