75
Chapter 5 – The Lipids: Triglycerides, Phospholipids, and Sterols
Learning Objectives
After completing Chapter 5, the student will be able to:
5.1 Recognize the chemistry of fatty acids and triglycerides and differences between saturated and unsaturated
fats.
5.2 Describe the chemistry, food sources, and roles of phospholipids and sterols.
5.3 Summarize fat digestion, absorption, and transport.
a. Trace the digestion of lipids including identification of enzymes needed and the role of bile.
5.4 Outline the major roles of fats in the body, including a discussion of essential fatty acids and the omega
5.5 Explain the relationships among saturated fat, trans fat, and cholesterol and chronic diseases, noting
recommendations.
5.7 Identify which fats support health and which impair it.
a. Name practical suggestions for food selections to replace saturated and trans fats with
monounsaturated and polyunsaturated fats.
Assignments and Other Instructional Materials
The following ready-to–use assignments are available in this chapter of the instructor’s manual:
• New! Case Study 5-1: Heart-Healthy Sandwich Choices
• Case Study 5-2: Heart-Healthy Diet Changes
• Worksheet 5-1: Trans Fat1
• Worksheet 5-2: Do You Know Your Fats?
• Worksheet 5-3: Check Your Lipid Choices2
76
• New! Handout 5-3: Butter and Margarine Labels Compared
• Handout 5-4: Cholesterol in Selected Foods
• New! Handout 5-5: Omega-3 Fatty Acid Content of Commonly Eaten Fish
• New! Handout 5-6: Potential Relationships among Dietary Saturated Fatty Acids, LDL Cholesterol, and Heart
Disease Risk
Visit the book’s instructor companion website to download:
• Handout 5-7: How to Use the Exchange System to Estimate Fat
Lecture Presentation Outline5
Key to instructor resource annotations (shown to the right of or below outline topics):
TRA = Transparency acetates: 13e = 13th edition, 12e = 12th edition, 11e = 11th edition, 10e = 10th edition
I. The Chemist’s View of Fatty Acids and Triglycerides
A. Fatty Acids – Explain fatty acids, including: IM HN 5-1
1. The Length of the Carbon Chain
2. The Number of Double Bonds – Define and explain the following:
a. Saturated fatty acids 10e TRA 40
b. Unsaturated fatty acids
1. Monounsaturated fatty acids (MUFA) 10e TRA 41
2. Polyunsaturated fatty acids (PUFA) 10e TRA 42
B. Triglycerides – Lipids with three fatty acids attached to a glycerol (Figure 5-2 and 5-3) 10e TRA 44, 45
C. Characteristics of Solid Fats and Oils 12e TRA 10; 13e TRA 10
1. Firmness – Explain how the degree of unsaturation impacts firmness (Figure 5–4)
a. Saturated fats
b. Polyunsaturated fats.
c. Short versus long fatty acid chains (Figure 5–5)
2. Stability – Explain how the degree of unsaturation impacts stability
a. Saturated fat
b. Monounsaturated fat
c. Polyunsaturated fat
d. Protection from rancidity
3. Hydrogenation (Figure 5-6) 10e TRA 47
77
II. The Chemist’s View of Phospholipids and Sterols
A. Phospholipids
1. Phospholipids in Foods 10e TRA 49
b. Lecithin (Figure 5-8)
B. Sterols – A well-known sterol is cholesterol
1. Sterols in Foods – Discuss the food sources of the sterols 10e TRA 50; IM HN 5-4
2. Roles of Sterols – Explain the roles and metabolism of sterols, including: IM HN 5-1
a. Bile acids, sex hormones, adrenal hormones, and vitamin D
III. Digestion, Absorption, and Transport of Lipids
A. Lipid Digestion – Explain the process of lipid digestion in the following anatomical areas (Figure 5–11):
1. In the Mouth
2. In the Stomach
3. In the Small Intestine 10e TRA 51, 52
a. Cholecystokinin (CCK) (Figure 5-12)
4. Bile’s Routes
1. Glycerol and short– and medium-chain fatty acids
2. Monoglycerides and long-chain fatty acids
C. Lipid Transport – Transport is made possible by a group of vehicles known as lipoproteins
10e TRA 54, 55, 56; 12e TRA 11
1. Chylomicrons (Figure 5-16)
2. VLDL (Very-Low-Density Lipoproteins)
a. Composed primarily of triglycerides
3. LDL (Low-Density Lipoproteins)
a. Composed primarily of cholesterol
b. Transport lipids to the tissues
4. HDL (High-Density Lipoproteins) (Figure 5-17)
5. Health Implications
1. Weight control
2. Replace saturated fat with monounsaturated fat and polyunsaturated fat in the diet
3. Soluble fibers
78
4. Phytochemicals
5. Moderate alcohol consumption
6. Physical activity
d. Genes influence lipoprotein activity
IV. Lipids in the Body – Explain the roles of lipids in the body, including:
A. Roles of Triglycerides 10e TRA 57
1. A source of energy for the cells
B. Essential Fatty Acids – Cannot be made by the body (Figure 5-19)
1. Linoleic Acid and the Omega-6 Family
2. Linolenic Acid and the Omega-3 Family
3. Eicosanoids
a. Made from arachidonic acid and EPA
b. Like hormones but have different effects on different cells
c. Include prostaglandins, thromboxanes, and leukotrienes
4. Omega-6 to Omega-3 Ratio – Experts disagree on the ideal ratio
5. Fatty Acid Deficiencies
C. A Preview of Lipid Metabolism
1. Storing Fat as Fat
2. Using Fat for Energy
a. Hormone-sensitive lipase dismantles triglycerides within adipocytes for release into the blood
b. Describe what occurs during fasting
c. Ketone bodies can be made from fat fragments
V. Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol
A. Health Effects of Saturated Fats, Trans Fats, and Cholesterol
1. Blood lipid profile
a. Reveals concentrations of lipids in the blood
4. Triglycerides 150 mg/dL
2. Heart Disease
a. Elevated blood cholesterol
b. Cholesterol accumulates in the arteries, restricts blood flow, and raises blood pressure
c. Saturated fat in the diet raises blood cholesterol
3. Cancer
4. Obesity – High fat intake combined with inactivity can lead to weight gain
79
B. Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol
1. The DRI and the 2010 Dietary Guidelines recommend fat at 20%-35% of energy intake (400-700
kcalories of a 2,000-kcalorie diet)
VI. Health Effects and Recommended Intakes of Monounsaturated and Polyunsaturated Fats
A. Health Effects of Monounsaturated and Polyunsaturated Fats
1. Heart Disease IM CS 5-1, 5-2
a. Benefits from monounsaturated fats and polyunsaturated fats
1. Replacing saturated fat and trans fat with monounsaturated fat and polyunsaturated fat is the
most effective dietary strategy in preventing heart disease (example: Table 5-3)
b. Benefits from omega-3 fats – Beneficial effects in reducing risk of heart disease and stroke,
supporting the immune system, and defending against inflammation
B. Recommended Intakes of Monounsaturated and Polyunsaturated Fats
1. AI have been established for linoleic and linolenic acids
2. AMDR: 5-10% kcal from linoleic acid, 0.6-1.2% kcal from linolenic acid
C. From Guidelines to Groceries IM WS 5-3, 5-5, HN 5-2, 5-3, 5-5, CA 5-1, 5-2, 5-3; Website HN 5-7
1. Protein Foods – Very lean and lean meats and meat alternates should be chosen
VII. Highlight: High-Fat Foods—Friend or Foe? IM HN 5-6
A. Guidelines for Fat Intake
1. It is recommended that individuals replace “bad” fats with “good” fats
B. High-Fat Foods and Heart Health 11e TRA 14
1. Cook with Olive Oil
C. High-Fat Foods and Heart Disease
1. Limit Fatty Meats, Whole-Milk Products, and Tropical Oils
a. Read food labels to determine those lowest in saturated fat
b. Choose leaner and lower-fat animal foods
80
2. Discuss foods included in this diet
E. Conclusion
1. Saturated fat and trans fat are poor for heart health
Case Studies6
Case 5-1: Heart-Healthy Sandwich Choices
Tom H. is a 35-year-old single man who works in a warehouse and takes his lunch to work every day. He is 69
inches tall and weighs 190 pounds. A recent blood test revealed that Tom’s total and LDL cholesterol levels are
abnormally high. He has been instructed to reduce his intake of saturated fat and to eat more unsaturated fats. He is
now at the grocery store looking for sandwich foods to pack in his lunches this week. He notes the following
information on the Nutrition Facts labels:
1. What should Tom notice about the cholesterol content of these foods?
2. Even though eggs are a significant source of cholesterol, what other information on the nutrition label should
Tom consider if he decides to buy eggs?
3. Which of the foods being considered by Tom most likely contains more unsaturated fats than saturated fats?
How can Tom derive this information from the information on the label?
4. What should Tom notice about the relationship between total fat content and kcalories in these foods?
5. What two foods listed here are major sources of saturated fat? What strategies might Tom use if he wants to
include them in his diet?
6. Using some or all of these foods plus other ideas from the “How to” feature in this chapter (p. 152), plan one
week (5 days) of sandwich ideas for Tom that are in line with his diet goals.
Answer Key
1. Cholesterol is only found in animal-based foods; there is no cholesterol in plant-based foods. Eggs are high in
cholesterol.
81
Case Study 5-2: Heart-Healthy Diet Changes
Dave is a 46-year-old attorney with a family history of heart disease (his father had a heart attack at the age of 56)
whose recent blood tests reveal high blood LDL cholesterol and triglyceride levels. His doctor has advised him to
eat less fat in his diet. Dave is a self–confessed “foodie” and he enjoys wine and cheese at several social functions
each week. He cooks with “real” butter at home and uses half milk and half cream in his coffee. Although fairly
inactive, Dave keeps his weight stable at 170 pounds. He is 5 feet 10 inches tall.
1. What factors may be contributing to Dave’s elevated cholesterol and triglyceride levels?
2. From the history given, identify the main sources of saturated fat in Dave’s diet. What are some reasonable
changes he could make to lower his intake of saturated fat from these foods?
3. Assume Dave eats about 2000 kcalories a day and that his doctor has advised him to limit his fat intake to 35
percent of his daily kcalories. Refer to the “How to” feature (p. 155) of this chapter to calculate his personal
Daily Value for fat.
4. According to the 2010 Dietary Guidelines for Americans, what is the maximum percentage of kcalories from
saturated fat that Dave should consume each day? Remembering that 1 gram of fat contains 9 kcalories,
calculate the maximum grams of saturated fat that Dave should eat each day based on his daily intake of 2000
kcalories.
5. Using information from Highlight 5, what additional advice would you offer Dave to improve his heart health?
6. Plan a one-day menu for Dave with higher amounts of healthful fatty acids and lower amounts of harmful fatty
acids.
Answer Key
1. Genetics (family history), excess alcohol consumption, diet high in saturated fat, inactivity.
Suggested Classroom Activities
Remember that, while they’re familiar to you, to a new student words such as glycerol, triglyceride, and lipoprotein
are a jumble of unfamiliar new terms. It takes time to assimilate this new information. It helps to define the terms
repeatedly as you lecture. To sustain motivation, interject information relevant to students and their personal lives.
Relate lipids to heart disease, cancer, obesity, and other subjects.
82
Classroom Activity 5-1: Compare Energy Values of Food Prepared by Different Techniques
Key concept: Effect of food preparation method on fat content Class size: Any
Instructions: Instruct students to calculate and compare the kcalories in a baked, broiled, or steamed food versus the
same food after frying. Use the table of nutrient composition of foods and fast foods in the appropriate appendix of
the textbook.
Classroom Activity 5-3: Fat in a Fast Lunch (Meal Comparison)8
Key concept: Applying fat recommendations to food choices Class size: Any
Instructions: Present the three quick lunch meal plans below to students and use the discussion questions to prompt
them to evaluate the plans.
Baby carrots, 1 cup
Discussion questions:
1. What are the recommended maximum intakes for an adult for fat, saturated fat, cholesterol and sodium? How
do these three lunch options fit within the recommendations?
2. Which lunch meal plan most represents the recommendations in the DASH diet plan? Why?
3. Which lunch is the highest in unsaturated fats?
4. How could you increase the omega-3 fatty acids in one of the lunches?
5. How could you improve the lunches from the fast food restaurants?
Answer key:
1. Daily Values: 65 g fat (based on 30% of 2000-kcal diet), 20 g saturated fat (based on 10% of 2000-kcal diet),
Nutrient composition of meals for instructor reference:
Lunch #1 Menu Item
Cal
Fat
SF
CH
Na
83
Lunch #2 Menu Item
Cal
Fat
SF
CH
Na
Subway Club, with American cheese, 12-inch, no sauce,
vegetables
700
16
7
100
2120
Bottled water
0
0
0
0
0
Totals
700
16
7
100
2120
Key: Cal = kcalories, Fat = total fat (grams), SF = saturated fat (grams), CH = cholesterol (milligrams), Na = sodium
(milligrams)
Classroom Activity 5-4: Discussion of Changing Guidelines for Fat Intake
Object: Exploring beliefs about fat Class size: Any
Instructions: Before students read this chapter, ask them to write on a sheet of paper their beliefs about fat intake
recommendations. Instruct them to be as specific as possible. Give them 5-10 minutes to complete this exercise.
Then ask each student to share what they believe and compile a list. You can tell them that this chapter explores the
basis for intake recommendations and can talk about the challenge of presenting nutrition information to the public.
How To “Try It” Activities Answer Key
How to Make Heart-Healthy Choices—by Food Group9
Type of milk (1 cup)
Whole
Reduced-fat
Low-fat
Nonfat
Total kcal
149
122
102
83
Fat (g)
7.98
4.83
2.37
0.20
% kcal from fat
48%
36%
21%
2%
How to Calculate a Personal Daily Value from Fat
58 g fat per day
How to Understand “% Daily Value” and “% kCalories from Fat”
%DV for fat = 6%; % kcal from fat = 31%
Study Card 5 Answer Key
1. Three classes of lipids are triglycerides, phospholipids, and sterols. In the body, fats (triglycerides) function to
provide energy, insulate the body, protect against physical shock, serve as part of cell membranes, and
Lunch #3 Menu Item
Cal
Fat
SF
CH
Na
Bread, whole-wheat, 2 slices
138
2
0.4
0
265
Peanut butter, chunky, 2 Tbsp
188
7.7
2.4
0
156
Jam, 1 Tbsp
56
0
0
0
6
Yogurt, low-fat, 1 cup
154
4
2.5
15
172
Grapes, 1 cup
67
0.4
0.1
0
2
Baby carrots, 1 cup
30
0.1
0
0
66
Totals
633
14.2
5.4
15
667
84
4. A triglyceride consists of a glycerol (a 3-C alcohol) molecule bonded to 3 fatty acids.
5. The hydrogenation process modifies unsaturated fats by adding H atoms to them, eliminating some or all of the
10. Lipoproteins are clusters of lipids associated with proteins that serve as transport vehicles for lipids in the
lymph and blood. They allow fat-soluble compounds to travel within watery body fluids. The lipoproteins differ
in size, composition, density, origin, and function. They rank this way from largest/least dense to smallest/most
15. Because foods made with solid fats provide abundant energy, but few if any essential nutrients, they contribute
to weight gain and make it difficult to meet nutrient needs. Solid fats also provide abundant saturated fat, trans
16. The DRI and Dietary Guidelines suggest a diet that provides 20-35% of the daily energy intake from fat, less
than 10% of daily energy intake from saturated fat, as little trans fat as possible, and less than 300 milligrams
17. c
18. Foods high in saturated fats include: whole milk, cream, butter, cheese, and ice cream; fatty cuts of beef and
pork; and coconut, palm, and palm kernel oils (the tropical oils and products containing them such as candies,
19. The Daily Value for fat for a 2000-kcal diet is 65 g—equivalent to 30% of kcal from fat.
20. b
85
Critical Thinking Questions10
1. Discuss how the structural/chemical properties of a fat affect its physical characteristics and stability.
2. Much attention has been placed on the negative association between trans fat intake and health/well-being.
Many states have gone so far as to literally ban trans fat from foods served in restaurants. Food labels are now
required to list the amount of trans fat on the label, but the majority of foods are now marketed as being free of
trans fat. Considering this, respond to the following questions: (1) Do you think that banning trans fat would
eliminate health damage from fat intake? (2) Can we assume that a food described on the label as trans fat free
contains no trans fat? (3) Does trans fat occur naturally in the diet independent of food processing?
3. Cholesterol has been linked to heart disease such that consumers recognize and try to limit their daily intake.
Can an individual live without ingesting cholesterol?
4. Explain how the concept of conditionally essential nutrients can be applied to lipid consumption.
5. Many consumers focus their selection process on choosing foods that are fat free and/or low in fat. Why has this
dietary choice not made much of a difference for most individuals, as indicated by present weight gaining trends
in the United States and other parts of the world?
6. What methods can the individual consumer use to adhere to the recommendations of less than 10% of
kilocalories from saturated fat and less than 300 milligrams of cholesterol per day on a long-term basis?
Answer Key
1. The structural design of lipids plays a key role in the presentation of physical characteristics and stability. Even
though fatty acids all have the same basic framework—long carbon chains inclusive of hydrogen with a methyl
group at one end and an acid at the other end—the arrangement and positioning of their atoms provides the
basis for differentiation. The length of the C chain and number/positioning of double bonds (if present) affect a
2. An interesting dilemma is posed by the banning of trans fat in many parts of the United States. On one side is
the idea that this protects consumers from a food component identified as a significant risk factor for the
development of chronic diseases such as heart disease and diabetes. On the other side of the discussion is the
idea that no one food component should be viewed as being exclusively bad since fats are needed both as
essential and non-essential nutrients. The key concern here is the amount of consumption of a specific fat
3. Cholesterol is a sterol substance that is manufactured in the body (endogenous) as well as outside of the body
(exogenous). Cholesterol is used to produce several key hormones and chemical substances in the body such as
vitamin D, bile acids, and sex and adrenal hormones. Cholesterol synthesis occurs in the liver, but cholesterol is
4. Conditionally essential nutrients are non-essential nutrients that become required nutrients as a result of specific
circumstances that exist in the body. This can occur as a result of growth, stress, and/or other medical
5. Even though consumers are more aware of food option choices such as fat free or low in fat, the marketed
product often contains other “hidden” components that influence weight gaining trends. For example, most
6. In order to minimize intake of saturated fats, one should restrict/limit the intake of animal foods containing solid
fats. Staying away from processed food selections will help to decrease intake of saturated and trans fats.
Including whole, fresh plant foods on a daily basis will be beneficial. It is important to consider not only dietary
IM Worksheet Answer Key
Worksheet 5-1: Trans Fat
1. To help consumers identify which foods contain trans fats, so that they can limit their intake of this type of fat
through their food choices.
3. During the hydrogenation process, which is used to solidify liquid vegetable oils and make them more resistant