This unit covers proteins, including essential and nonessential amino acids. It describes protein digestion, absorption, transport and metabolism in the body. Key functions of protein include building body components, maintaining fluid balance, and contributing to immune function. Recommended dietary allowances for protein are provided. High-protein diets can increase risk for diseases if animal protein intake is high. Protein-energy malnutrition results from inadequate protein and energy intake. Meeting protein needs through vegetarian diets requires planning but can be healthy.

1. UNIT 6
PROTEINS
Chapter 6

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

4. Classification of Amino Acids

5. Protein Content of Foods

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

9. Meat Foods: Essential AA

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

11. Complementary Proteins

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)

13. Lean & Complete Protein

14. Artificial Chickens?

15. Fish Anyone?

16. Me & My Friends

17. Hold the Beef

18. Where’s the Beef?

19. No Beef with you, Dude!

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

24. Protein Digestion & Absorption

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

28. Protein Metabolism

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

34. Nitrogen Balance & Protein Needs

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

38. Protein-Energy Malnutrition

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

40. Types of Vegetarian Lifestyles
 Vegan
 Only plant food
 Fruitarian (not recommended)
 Primarily fruits, nuts, honey & vegetable oils
 Lactovegetarian
 Plant products & dairy products
 Lactoovovegetarian
 Plant products, dairy products & eggs

41. Nutrients of Concern
 Riboflavin
 Dairy group & green leafy veggies
 Vitamin D
 Enriched dairy group & soy or plant milk & sun exposure
 Vitamin B12
 Meats, vitamin B-12-fortified foods
 Iron
 Meats, grains group, whole-grains, dried fruits & nuts
 Zinc
 Meat, whole-grains, cereals, nuts & legumes
 Calcium
 Dairy group, Ca-fortified foods & dark-green leafy veggies

42. MyPlate for Vegetarians

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!)