Proteins and Vegetarianism

Lecture 5 Units 15, 16

Chemistry

Composition: C H O N (S) Amino Acids “building blocks”

– Amine group (NH2)

– Acid group (COOH)– Differ by side group (“R”)

9 : from food 11 Nonessential AA: can be made from other

AA

Amino Acid, Peptide & Protein

Amino acid

NH2

R C COOH

Peptide and protein

AA1-AA2-AA3-AA4--- AAn

Digestion & Absorption

HCl

Enzymes split long chain of AA for absorption

Blood transports AA to liver & muscle

Functions of Protein

Growth, build & maintenance of tissues Regulate body processes:

Water (fluid) balance--prevent edema Acid-Base (pH) balance--buffers Immune system - antibodies

Energy source--4 calories / gram

Protein Synthesis

DNA code controls : Which AA needed What order AA go on new chain

AA3

AA1 + AA2 AA1AA2 AA1AA2AA3

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

Breakdown of protein to AA

AA converted to fat when excess AA

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 Complete Protein

High qualityAll essential AA in needed amounts Animal sources

Incomplete Protein

Plant sources 70% of protein from

animal sources in US

Complementary Protein

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

Plants provide Incomplete Protein

Low in one or more ess. AA

Eat in combo to “complete” the AA balance

Protein Requirements .8 gm/kg body weight Protein RDA

46 gm for women

58 gm for men

10-12% kcal from protein Actual US Intake

>80 gm

>110 gm

~17% kcal from protein

Food Sources of Proteins

Meat Fish Poultry Eggs

Beef & pork rich in iron but high in fat

More Good Protein Sources

Dairy products select low fat (butter not protein)

Legumes Cereal grains Seeds Nuts Plant sources of

protein are low in fat

What about protein for athletes? Athlete needs 1.26 gm /

Kg (~90 gm) (but typical US male

eats >110 gm and female eats >80 gm)

Thus… supplements not needed

What does the body do with the added amino acid?

What builds muscle: exercise and a good diet

Amino Acid Supplement

High intake of a single AA leads to AA imbalance and is harmful

Many AA supplements on market, Surplus of AA causes diarrhea, loss of

appetite, GI upsets Tryptophan supplements were banned

in 1990 Athletes

Vegetarian Diets

Semi-vegetarian:– lacto vegetarian– ovo vegetarian

Strict vegetarian:– “Vegan”– healthy diets use complementary proteins

Macrobiotic diet: locally grown and whole foods; Yin(“cold”)&yang(“warm”) foods

Vegetarian Diets & Health

Associated with low risk of chronic diseases

May lead to Vegans: vitamins B12 and D, Ca, Zn are

at risk Adequately planned vegetarian diets

can The key to achieve healthy diet: variety

Protein deficiency--Marasmus

Chronic food deprivation,diseases

Protein & calories Impairs brain

development & learning

Severe weight loss Infection, diarrhea

Protein deficiency --Kwashiorkor Deficiency in protein but

not calories Children 1-3 years Some weight loss Edema

Hair: dry, brittle, changes color (lack of AA to make melanin)