1. taught by Norman D. Sossong, MD, PhD NSCC – NTR150 – Spring 2008
Chapter 5 - Fats
taught by Norman D. Sossong, MD, PhD NSCC – NTR150 – Spring 2008

2. Fat: An Essential Energy-Supplying Nutrient

3. What Are Fats? Fats are one type of lipid.
Lipids: diverse class of molecules that are insoluble in water.
Lipids (fats) do not dissolve in water.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

4. Lipids Description: A nonpolar, organic molecule Fatlike
Insoluble in water
Dissolve readily in nonpolar organic solvents

5. Lipid Types
Fats
Oils
Waxes
Steroids
Phospholipids
Carotenoids

6. What Are Fats? Three types of lipids are found in foods: Triglycerides
Phospholipids
Sterols
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

7. Lipids: Fats = Triglycerides
Composed of:
Glycerol
Fatty acids
Ratio of H:O > 2:1

8. Triglycerides Triglycerides are composed of Three fatty acid molecules
Fatty acids are long chains of carbon atoms surrounded by hydrogen atoms
One glycerol molecule
Glycerol is a 3-carbon alcohol that is the backbone of a triglyceride
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

9. Triglycerides
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

10. Glycerol
A 3-carbon alcohol
One hydroxyl group on each carbon

11. Glycerol + 3 Fatty Acids → Triglyceride

12. Fatty acids Long hydrocarbon chains ending in a carboxyl (-COOH) group
Typical length is 14 to 20 carbon atoms

13. Fatty Acids in Triglycerides
Fatty acids can differ in
Length of their carbon chain
Level of saturation
Shape
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

14. Fatty Acids Differ in Length
Short-, medium-, or long-chain
Chain Length
4-24 carbons
Typical length;
14-24 carbon atoms

15. Fatty Acids in Triglycerides
Fatty acids can differ in
Length of their carbon chain
Level of saturation
Saturation refers to how many hydrogen atoms surround each carbon
Shape
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

16. 3 Types of Fatty acids
Saturated
Unsaturated
Polyunsaturated

17. Fatty acids
Saturated
All the internal carbon atoms have single bonds with either C or H
This represents the maximum amount of H atoms that can be attached
(Animal fats are typically saturated)

18. Saturated Fat

19. Fatty acids: Levels of Saturation
Saturated
Unsaturated
One, or more, of the carbons are attached with 2 or 3 bonds
Bend at the double bonds
(Most plant fats are unsaturated;
Palm & coconut oils are notable exceptions)

20. Unsaturated Fat

21. Fatty acids: Levels of Saturation
Saturated
Unsaturated
Polyunsaturated
There are 2 or more double bonds
Bend at the double bonds →
Low melting points
Usually liquid at room temperatures = oil

22. Polyunsaturated Fat Polyunsaturated There are 2 or more double bonds
Bend at the double bonds →
Low melting points
Usually liquid at room temperatures = oil

23. Polyunsaturated Fat

24. Fatty Acids: Level of Saturation
Degree of saturation
Saturated
All single bonds between carbons
Monounsaturated
One carbon-carbon double bond
Polyunsaturated
More than one carbon-carbon double bond

25. Lipids: Fats = Triglycerides
Physical Properties
Saturated Fats
Tend to be solids at room temperature
Unsaturated Fats
Tend to be liquids at room temperature
Applications & Sources
Tend to be structurally useful in land animals
Tend to be found in cold-water fish & plants

26. Triglycerides Fatty acids can differ in Length of their carbon chain
Level of saturation
Shape
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

27. Triglycerides
The shape of a triglyceride is determined by the saturation of the carbon chains.
Saturated fatty acids can pack tightly together and are solid at room temperature.
For example animal fats, butter, and lard are high in saturated fatty acids.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

28. Triglycerides
Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain.
Monounsaturated fatty acids lack hydrogen atoms in only one region.
Polyunsaturated fatty acids lack hydrogen atoms in multiple locations.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

29. Triglycerides
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

30. Triglycerides
Unsaturated fatty acids do not stack together well and are liquid at room temperature.
Plant oils have unsaturated fatty acids.
The hydrogen atoms at the unsaturated region can be arranged in different positions:
Cis – same side of the carbon chain
Trans – opposite sides of the chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

31. Fatty acids Saturated Unsaturated Polyunsaturated
Cis- vs. trans- fatty acids

32. Triglycerides
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

33. Fatty Acids Are Key Building Blocks
Types of fatty acids
Cis and trans
Hydrogenation produces trans fatty acids

34. Triglycerides
Hydrogenation: The addition of hydrogen atoms to unsaturated fatty acids.
Coverts liquid fats (oils) into a more solid form
Used to create margarine from plant oil
Often creates trans fatty acids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

35. Fatty Acids Are Key Building Blocks
Types of fatty acids
Cis and trans
Hydrogenation produces trans fatty acids
Essential fatty acids
Linoleic acid and alpha-linolenic acid
Can’t be made in the body
Used to make eicosanoids

36. Triglycerides = Fats Structure Functions Glycerol + 3 fatty acids
Energy source and reserve
Insulation and protection
Carrier of fat-soluble vitamins
Sensory qualities in food

37. Lipids: Fats = Triglycerides
Used to store energy in organism
9 kilocalories (kcal)/gram
[compared with 4 kcal/gram for carbohydrates]
Saturated fats tend to have more energy than unsaturated fats
2 C-H vs. 1 C=C
→ animal fats usually have more calories than do vegetable fats

38. Triglycerides in Food Sources of omega-3 fatty acids
Soybean, canola, walnut, flaxseed oils
Salmon, tuna, mackerel
Sources of omega-6 fatty acids
Vegetable oils
Nuts and seeds
Photos © PhotoDisc

39. What Are Fats? Three types of lipids are found in foods: Triglycerides
Phospholipids
Sterols
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

40. Phospholipids Are composed of Glycerol backbone 2 fatty acids
Phosphate
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

41. Phospholipids Are composed of Glycerol backbone 2 fatty acids
Phosphate
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

42. Phospholipids Modified fats
= a triglyceride with one fatty acid chain replaced by a phosphate-containing group

43. Phospholipids Composed of Polar “head” (phosphate group) at one end
2 nonpolar “tails” at the other end

44. Phospholipids Composed of Polar “head” (phosphate group) at one end
2 nonpolar “tails” at the other end

45. Phospholipids Form bilipid layers which form biological membranes
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

46. Phospholipids Are soluble in water
Are manufactured in our bodies; so they are not required in our diet
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

47. Phospholipids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

48. Phospholipid

49. Phospholipids: Summary
Structure
Glycerol + 2 fatty acids + phosphate group
Functions
Component of cell membranes
Lipid transport as part of lipoproteins
Emulsifiers
Food sources
Egg yolks, liver, soybeans, peanuts

50. What Are Fats? Three types of lipids are found in foods: Triglycerides
Phospholipids
Sterols
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

51. Sterols Sterols: Lipids containing multiple rings of carbon atoms.
Are essential components of cell membranes and many hormones
Are manufactured in our bodies and therefore are not essential components of our diet
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

52. Sterol

53. Sterols
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

54. Cholesterol

55. Cholesterol

56. Sterols: Cholesterol Functions Synthesis Food sources
Component of cell membranes
Precursor to other substances
Sterol hormones
Vitamin D
Bile acids
Synthesis
Made in the liver
From saturated fats
Food sources
Found only in animal foods

57. Steroids Composed of 4 carbon rings Examples Cholesterol Estrogen
Progesterone
Aldosterone
Testosterone

58. From Cholesterol to Sex Hormones

59. Estrogen – Testosterone Differences

60. Lipid and Lipid-Related Molecules

61. Digestion of Fats
Fats are not digested and absorbed easily because they are insoluble in water.
No digestion of fats occurs in the watery environments of the mouth or stomach.
Digestion of fats begins in the small intestine.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

62. Digestion of Fats As fat enters the small intestine
Bile is secreted from the gall bladder into the small intestine
Bile is produced by the liver and stored in the gall bladder
Bile disperses fat into smaller fat droplets
Pancreatic enzymes break fat into 2 separate fatty acids and a monoglyceride
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

63. Digestion of Fats
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

64. Digestion and Absorption
Mouth and stomach
Minimal digestion of triglycerides
Small intestine
Emulsified by phospholipids
Digested by pancreatic lipase
Absorbed into intestinal cells
Formed into chylomicrons and moved into lymphatic system

65. Digestion of Fats
Fatty acids are arranged as lipoproteins for absorption and transport.
Chylomicron: A lipoprotein produced by cells lining the small intestine.
Composed of fatty acids surrounded by phospholipids and proteins
Soluble in water
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

66. Structure of a Lipoprotein
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

67. Digestion of Fats
Chylomicrons are absorbed by cells of the small intestine, then
Travel through the lymphatic system
Transferred to the bloodstream
Short- and medium-chain fatty acids are absorbed more quickly since they are not arranged into chylomicrons.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

68. Digestion of Fats
Triglycerides in the chylomicrons must be disassembled by lipoprotein lipase before they can enter body cells.
After entering body cells, triglycerides can be
Used immediately for energy
Used to make lipid-containing compounds
Stored in liver and muscle cells
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

69. Cholesterol Transport in Blood
Lipoproteins
Chylomicrons
VLDL = Very Low Density Lipoproteins
LDL = Low Density Lipoproteins
HDL = High Density Lipoproteins

70. Lipids in the Body Lipoproteins carry lipids around the body
Chylomicrons
Delivers dietary lipids from intestines to cells and liver

71. Lipids in the Body Very-low-density lipoproteins (VLDL)
Deliver triglycerides to cells
Low-density lipoproteins (LDL)
Deliver cholesterol to cells
High-density lipoproteins (HDL)
Pick up cholesterol for removal or recycling

72. Lipoprotein Composition

73. The Role of Fat
Energy
Fat is very energy dense, containing 9 kcal per gram.
Much of the energy used during rest comes from fat.
Fat is used for energy during exercise, especially after glycogen is depleted.
Fat is also used for energy storage.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

74. The Role of Fat Essential fatty acids
Two fatty acids cannot be synthesized in the body and must be obtained in the diet
Alpha-linoleic acid (omega-3 fatty acid)
Found in vegetables, fish and fish oils
Linoleic acid (omega-6 fatty acid)
Found in vegetable and nut oils
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

75. The Role of Fat Fat-soluble vitamins
Vitamins A, D, E, and K are soluble in fat; fat is required for their transport
Fat is essential to many body functions
Cell membrane structure
Nerve cell transmissions
Protection of internal organs
Insulation to retain body heat
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

76. The Role of Fats Fat provides flavor and texture to foods.
Fat contributes to making us feel satiated because
Fats are more energy dense than carbohydrates or protein
Fats take longer to digest
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

77. How Much Fat?
The Acceptable Macronutrient Distribution Range (AMDR) for fat:
20-35% of calories should be from fat
Athletes and highly active people may need more energy from carbohydrates and can reduce their fat intake to 20-25% of total calories.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

78. How Much Fat? The type of fat consumed is important.
Saturated fat should be no more than 7% of total calories.
Trans fatty acids should be reduced to the absolute minimum.
Most fat in our diets should be from monounsaturated fats (eg., olive oil).
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

79. Food Sources of Fat Visible fats Invisible fats
Fats we knowingly add to foods
Butter, cream, mayonnaise, dressings
Invisible fats
Fats hidden in foods
Naturally occurring or added during processing
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

80. Lipids in the Diet Recommended intake
Reduce saturated and trans fat intake
Saturated fats → ↑ cholesterol production
Trans fat → ↑ risk of heart attacks
Total fat: 20-35% of calories
Need ~ 2% of calories as essential fatty acids
Improve balance of
omega-3: omega-6 fatty
acids
Photos © PhotoDisc

81. What are sources of highly saturated fats?
Animal products such as:
Lard
Pork
Beef
Lamb
Chicken fat
Butterfat
Cream
Butter
Cheese
(Note: fish oil is not very saturated)

82. What are sources of highly saturated fats?
Vegetable products such as:
Coconut oil
Palm oil
Chocolate
Note: both coconut oil and palm oil are widely used in prepared foods such as:
Cakes
Puddings
Frozen dinners

83. Unsaturated Fats Are oils at Room Temperatures
Help reduce cholesterol in the blood
Types:
Monounsaturated
Polyunsaturated

84. Monounsaturated Fat Sources
Olive oil
Canola oil
Peanut oil
Almonds
Avacados
Cashews

85. Polyunsaturated Fat Sources
Corn oil
Soybean oil
Safflower oil
Sunflower oil
Cottonseed oil
Sesame oil
Walnuts

86. Cholesterol Sources Not made by plants Animal kingdom Humans
Liver
Saturated fats  the amount made
Foods of animal origin

87. Foods of Animal Origin That Act as Cholesterol Sources
Shell fish
Meats
Poultry
Egg yolks (but not egg whites)
Cream (and products made from cream)
Butter
Cheese
Ice cream

88. Lipids and Health Obesity Heart disease Cancer
High fat diets promote weight gain
Heart disease
High saturated and trans fat intake raises LDL cholesterol
Cancer

89. Health Problems From Fat
Cardiovascular disease
Dysfunction of the heart or blood vessels
Can result in heart attack or stroke
The type of fat in our diet can contribute to or protect against cardiovascular disease.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

90. Cardiovascular Disease
Risk factors for cardiovascular disease include
Being overweight
Physical inactivity
Smoking
High blood pressure
Diabetes
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

91. Cardiovascular Disease
Blood lipids include
Chylomicrons
VLDLs – very low-density lipoproteins
LDLs – low-density lipoproteins
“bad cholesterol”
HDLs – high-density lipoproteins
“good cholesterol”
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

92. Types of Blood Lipids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

93. Cardiovascular Disease
Diets high in saturated fats
Decrease the removal of LDLs from the blood
Contribute to the formation of plaques that can block arteries
Increase triglyceride levels (chylomicrons and VLDLs)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

94. Cardiovascular Disease
Cross-section of (a) a normal artery and (b) a partially blocked artery.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

95. Cardiovascular Disease
Trans fatty acids:
Can raise blood cholesterol levels as much as saturated fat
Are abundant in hydrogenated vegetable oils (margarine, vegetable oil spreads)
Should be reduced to the absolute minimum
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

96. Cardiovascular Disease
How can fat intake protect against heart disease?
Diets high in omega-3 fatty acids (along with moderate exercise) can increase HDL “good” cholesterol levels.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

97. Lipids in the Diet Fat substitutes Different types of composition
Olestra
Sucrose + fatty acids
Indigestible – provides zero kcals
Reduces absorption of fat-soluble vitamins