Proteins and Vegetarianism Lecture 5 Units 15, 16
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 quality
All 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)