2. Student Learning Outcomes
This unit is designed to allow you to:
Distinguish between essential & nonessential amino acids
& protein of high & low quality & describe the concept of
complementary protein.
Describe protein digestion, absorption, transport &
metabolism in the body & list main functions of protein.
Identify food sources of protein & follow recommendations
to determine protein needs for healthy adults.
Describe the harmful effects of a high-protein diet &
protein balance & imbalance.
Describe protein-calorie malnutrition & disease.
Describe vegetarian diets plans to meet healthy needs.
3. Proteins
Much of the body is made of protein
Highest after water in lean men, ~17% of body weight
Supply N & S (which amino acids?)
Supply energy & regulate & maintain body
functions
Most people in the US & Canada eat diets rich in
protein
Diets in developing countries often contain
insufficient amounts of protein
Compromised immune system leads to many infectious &
diseases sometimes fatal
Normal growth & development is also compromised
6. My Plate: Sources of Protein
Grains group: bread, cereals, rice, noodles
2-3 g per serving
Veggies group: carrots, corn, broccoli
2-3 g per serving
Fruits group: apples, oranges, bananas
< 1 g per serving
Dairy group: milk, yogurt, cheese
8-10 g per serving
Protein group: meat, poultry, eggs, fish, beans, nuts
7 g per serving
7. Protein Quality
High quality or complete protein
Contains ample amount of all EAA
Typically, animal protein (except gelatin)
Low quality or incomplete protein
Deficient or low in one or more EAA
Typically, plant protein (except soy protein)
Limiting amino acid
Protein cannot be assembled
All-or-none principle
8. Characteristics of Animal Protein
Complete
High digestibility
Good source of some minerals
Fe, Zn, Se
Good source of some vitamins
Thiamin, niacin, riboflavin, B-6, B-12
Affordable?
High in SFA
No fiber
No phytochemicals
Low in antioxidants
10. Characteristics of Plant Protein
Incomplete
Low digestibility
Good source of some minerals
Mg, Mn, K
Good source of some vitamins
A, C, E, K, folate
Affordable
Low in SFA
Good source of fiber
Good source of phytochemicals
High in antioxidants
12. EAA Deficient in Plant Proteins
One or more essential amino acids are
deficient in most plant proteins
Lysine
Limiting in some grains (like rice) & nuts
Methionine
Limiting in legumes & veggies
Tryptophan
Limiting in some grains (like corn)
20. Cattle Inventory (www.cattlenetwork.com)
United States 89,800,000
Rank State 2015 % of U.S.
1 Texas 11,800,000 13.14%
2 Nebraska 6,300,000 7.02%
3 Kansas 6,000,000 6.68%
4 California 5,150,000 5.73%
5 Oklahoma 4,600,000 5.12%
6 Missouri 4,000,000 4.45%
7 Iowa 3,900,000 4.34%
8 South Dakota 3,700,000 4.12%
9 Wisconsin 3,500,000 3.90%
10 Colorado 2,600,000 2.90%
11 Montana 2,500,000 2.78%
12 Minnesota 2,330,000 2.59%
21. Cattle Inventory (www.cattlenetwork.com)
United States 89,800,000
Rank State 2015 % of U.S.
38 West Virginia 370,000 0.41%
39 South Carolina 335,000 0.37%
40 Vermont 260,000 0.29%
41 Maryland 185,000 0.21%
42 Hawaii 135,000 0.15%
43 Maine 85,000 0.09%
44 Connecticut 47,000 0.05%
45 Massachusetts 38,000 0.04%
46 New Hampshire 30,000 0.03%
47 New Jersey 28,000 0.03%
48 Delaware 17,000 0.02%
49 Alaska 10,000 0.01%
50 Rhode Island 5,000 0.01%
22. Lean Protein!
Legumes are rich
sources of protein
One-half cup meets
about 10% of protein
needs but contributes
only about 5% of
energy needs
They are also cheap,
rich sources of fiber,
phytochemicals & have
low fat & SFA
Lean protein!
23. Mix Them Up!
Small amounts of
animal protein in a
meal quickly up to
meet daily protein
needs
Plant protein adds fiber
& phytochemicals &
decreases the intake of
total fat & SFA
Reduces the cost of
meals too
25. Dietary Protein Digestion
Dietary protein stimulates the release of CCK, secretin
& GIP (gastric inhibitory peptide) from small intestine.
Cholecystokinin (CCK) stimulates the release of
zymogens from the pancreas & bile from gallbladder.
Secretin stimulates pancreas to release HCO3
-.
GIP inhibits gastric motility.
Activation of pancreatic zymogens by trypsin.
Enzymes will break peptides mostly into amino acids.
Amino acids absorbed actively with Na+ gradient.
Absorbed AA transported to liver via portal vein.
26. Digestion of Dietary Protein
Zymogen Activation Source Specificity
Pepsinogen [HCl] & pepsin Chief cells of
stomach
Mostly
phenylalanine
Trypsinogen Enteropeptidase
& trypsin
Pancreas Lysine & arginine
Chymotrypsinogen Trypsin &
chymotrypsin
Pancreas Aromatic & bulky
amino acids
Proelastase Trypsin Pancreas Small AA
Ala/Gly/Ser
Procarboxypeptidase
A/B
Trypsin Pancreas Carboxy-end of
peptide
Aminopeptidases
(membrane-bound)
None Small intestine Amino-end of
peptide
Enteropeptidase None Small intestine Trypsin
27. Absorption of Amino Acids
Secondary active transport using Na-AA
carriers.
Absorbed are AA taken to liver via portal vein.
In early infancy (4-5 months) GI tract is
permeable to peptides, so proteins from cow’s
milk & eggs may predispose an infant to food
allergies.
It is recommended waiting until an infant is one
year or older before introducing common
allergenic foods
Such as cow’s milk & eggs
29. Processing of Amino Acids
Amino transfer (transamination by NBCE)
All AA except Lys & Leu
By aminotransferases (or transaminases, liver)
PLP (vitamin B-6) enzymes
Cytosol & mitochondria
Oxidative deamination
Only Glu undergoes this reaction
Glutamate dehydrogenase (very active in liver)
NAD+/NADP+ (niacin) enzyme
Cytosol & mitochondria
30. Functions of Proteins
Building blocks of body components
Cell major component after water
Muscle
Enzymes
Hormones
Antibodies
Visual pigments
Maintain fluid balance
Blood protein (3.5-5.5 g/100 ml, about 50% is albumin)
If below, swelling of tissues occurs (edema)
Contribute to acid/base balance
Serum albumin
hemoglobin
31. Functions of Proteins
Enhance the immune system
Minimum protein in blood to have a strong immune
system
If below, very weak immune system (anergy) & common
diseases can be fatal
Form glucose
Most AA are glucogenic
Only Lys & Leu are not
Provide energy
Long-duration exercise increases energy use from AA
It needs lots of processing by liver & kidneys via
gluconeogenesis
32. Functions of proteins
Vitamin source
Niacin can be synthesized from tryptophan
Contribute to satiety
Compared to other macronutrients, proteins
provide the highest feeling of satiety after a meal
33. Protein & Fluid Balance
Blood proteins are
important for
maintaining the
body’s fluid balance
Without sufficient
protein in the blood,
edema develops
35. RDA for Protein
0.8 g per kg of HBW
72.7 kg x 0.8 g/kg = about 58 g of protein
Increased by ~10-15 g/day during pregnancy
Endurance athletes may need 0.8-1.7 g per kg of
healthy weight
RDA represents about 8-10% of total cal
Typical American gets about 15% of protein calories
Most of us eat more than the protein RDA
Excess protein cannot be stored as protein
FNB advises against protein intakes greater than
35% of total calories
36. High-Protein Diets
FNB is against protein over 35% of energy intake
Excess protein does not provide additional health
Protein up = animal protein up!
Low in fiber, some vitamins & minerals &
phytochemicals
Intake of animal protein increases risk for heart
disease
High in total, SFA (& TFA) & calories (& sodium)
Excessive intake of red meat is linked with colon
cancer & extra burden on the kidneys
Kidneys stones
Increase calcium loss
37. Individual AA Supplements
Supplement may cause imbalances & toxicity
(especially with methionine, cysteine & histidine)
Body is designed to handle whole proteins
Supplement can overwhelm the absorptive
mechanism
Excess of one AA can hamper absorption of other
AAs
Protein cannot be made if one AA is missing
In Canada the sale of individual amino acids is
banned
39. Vegetarian & Plant-Based Diets
Becoming more prevalent
About 2.5% in the US & about 4% in Canada
About 20-25% of Americans appears to go
meatless 4 times per week
Many reasons for going green
Religious, philosophical, ecological, economical
or health-related
Can meet nutritional needs with proper
planning
↓death rates from many chronic diseases
43. The New American Plate
For cancer prevention
Two thirds (or more) veggies, fruits, whole
grains & beans
One third (or less) lean animal protein
44. AICR Guidelines for Cancer Prevention
Choose a diet rich in a variety of plant-based
foods
Eat plenty of veggies & fruits
Maintain a healthy weight & be physically
active
Drink alcohol in moderation, if at all
Select foods low in fat & salt
Prepare & store food safely
45. Albert’s Unknown Formula
"Nothing will benefit human health &
increase the chances for survival of life on
Earth as much as the evolution to a
vegetarian diet."
Albert Einstein
46. Vegetarian Infants & Children
Highest at risk for deficiency
Ensure adequate intake of iron, vitamin B12,
vitamin D, calcium
High-fiber diet may prevent infants or
children from meeting energy needs
Replace whole-grain products with refined grain
products, fruits juices & peeled fruits
47. My Intake of Protein
About 2300 cal total (EER ~2400 cal)
~100 g protein ( ~17% cal)
~293 g carbs, ~68 g fat & ~15 g alcohol
Total protein about ~100 g
~17% of cal (10-35% of cal, FNB)
70.9 kg x 0.8 g/kg = ~57 g protein (1.7-RDA equivalents)
About 40% plant protein
Beans, nuts, peanut & almond butters, veggies & whole grains
About 60% animal protein
Mostly from fish, chicken, eggs & sharp cheddar cheese
Beef rarely (every 4-5 months lately!)
