CHAPTER 5 LIPIDS

Chapter 5
The Lipids: Fats, Oils,
Phospholipids, and
Sterols
Sizer and Whitney, Nutrition: Concepts and Controversies, 15th
Edition. © 2020 Cengage. All Rights Reserved. May not be
scanned, copied or duplicated, or posted to a publicly accessible
website, in whole or in part.

Sizer and Whitney, Nutrition: Concepts and Controversies, 15th Edition. © 2020 Cengage. All Rights Reserved.
May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
Learning Objectives (Slide 1 of 2)
• Describe the usefulness of lipids in the body and in food
• Compare the physical and chemical properties and the
functions of the three categories of lipids
• Describe the processes of digestion, absorption, and
transportation of lipids in the body
• Describe how fats are stored and used by the body
• State the significance of blood lipoproteins and dietary
fats to health
• Summarize the functions of essential fatty acids

Learning Objectives (Slide 2 of 2)
• Outline the process of hydrogenation and its effects on
health
• Identify the sources of fats among the food groups
• Describe ways to reduce solid fats in an average diet
• Discuss both sides of the scientific debate about current
lipid guidelines

Introducing the Lipids
• Diet moderate in fats
• Lipids are necessary and valuable
• Three classes of lipids
• Triglycerides
• Phospholipids
• Sterols

Table 5.1: The Usefulness of Fats (Slide 1 of 2)
Fats in the Body Fats in Food
Energy fuel. Fats provide 80 to 90
percent of the resting body’s energy
and much of the energy used to fuel
muscular work
Nutrients. Food fats provide essential
fatty acids, fat-soluble vitamins, and
other needed compounds
Energy stores. Fats are the body’s
chief form of stored energy
Transport. Fats carry fat-soluble
vitamins A, D, E, and K along with
some phytochemicals and assist in
their absorption
Emergency reserve. Fats serve as an
emergency fuel supply in times of
severe illness and starvation
Energy. Food fats provide a
concentrated energy source
Padding. Fats protect the internal
organs from shock, cushioning them
with fat pads inside the body cavity
Sensory appeal. Fats contribute to the
taste and smell of foods

Table 5.1: The Usefulness of Fats (Slide 2 of 2)
Fats in the Body Fats in Food
Insulation. The layer of fat under the
skin insulates the internal tissues
against cold temperatures
Appetite. Fats stimulate the appetite
Cell membranes. Fats form the major
material of cell membranes
Texture. Fats make fried foods crisp
and other foods tender
Raw materials. Lipids are converted to
other compounds, such as hormones,
bile, and vitamin D, as needed
Satiety. Fats in foods contribute to
feelings of fullness

How Are Fats Useful to the Body?
• Chief storage form for the energy from excess food
• Adipose tissue
• Secretes hormones to regulate appetite
• Fat storage efficiency
• Purposes of fat
• Shock absorbers and insulators
• Cell membranes
• Transport (of vitamins and phytochemicals)
• Raw material (for lipid hormones, bile, and vitamin D)

Figure 5.1: A Fat Cell

How Are Fats Useful in Food? (Slide 1 of 2)
• Concentrated calorie source
• Lots of energy in small packages
• Fat-soluble nutrients
• Vitamins
• Essential fatty acids
iStock.com/smpics

How Are Fats Useful in Food? (Slide 2 of 2)
• Sensory qualities
• Aromas
• Flavors
• Tenderness
• Satiety
• Slows down food movement

Triglycerides: Fatty Acids and Glycerol
• Triglycerides
• Three fatty acids attached to
glycerol molecule
• Fatty acid differences
• Chain length
• Degree of saturation
• Each animal species
makes its own
characteristic kinds of
triglycerides

Saturated versus Unsaturated Fatty Acids
• Saturation
• Every bond from the carbons in a fatty acid is holding a hydrogen
atom
• Levels of saturation
• Saturated
• Unsaturated
• Polyunsaturated fatty acid
• Monounsaturated fatty acid

Figure 5.4: Three Types of Fatty Acids
Saturated Monounsaturated Polyunsaturated
†These points of unsaturation can also be referred to as double bonds.

Fatty Acids
• Melting point
• Varies with the degree of saturation
• Fat hardness
• Softer generally is healthier
• Sources of fatty acids
• Vegetable and fish oils
• Animal fats

Figure 5.6: Fatty Acid Composition of
Common Food Fats
aThese families of polyunsaturated fatty acids are explained in
a later section.
bSalad or cooking type more than 70% linoleic acid.
cFish oil average values derived from U S D A data for salmon,
sardine, and herring oils.
Note: The U S D A Nutrient Database (http://ndb.nal.usda.gov)
lists the fatty acid contents of many other foods.

Phospholipids and Sterols
• Phospholipids
• Glycerol containing two fatty
acids and a phosphorus
molecule
• Soluble in water and fat
• Emulsifier
• Sterols
• Rings of carbon with side
chains of carbon, hydrogen,
and oxygen
• Cholesterol has roles in the
body
• Plant sterols
Bill Steele/Getty Images

How Are Fats Digested and Absorbed? (Slide
1 of 2)
• Digestion
• Stomach
• Small intestine
• Bile
• Gallbladder
• Absorption
• Fatty acids split from glycerol
• Fatty acids, phospholipids, and monoglycerides
• Bile shuttles lipids across mucus layer
• Up to 98 percent of fats consumed are absorbed
• The more fat taken in at a meal, the slower the digestive system
action

How Are Fats Digested and Absorbed? (Slide 2 of 2)
Fat and watery
digestive juices tend to
separate. Enzymes are
in the water and can’t
get at the fat.
When fat enters the
small intestine, the
gallbladder secretes bile.
Bile compounds have an
affinity for both fat and
water, so bile can mix
the fat into the water.
After emulsification,
more fat is exposed to
the enzymes and fat
digestion proceeds
efficiently.

Figure 5.9: The Process of Lipid Digestion and
Absorption
1 - In the mouth and stomach: Little fat digestion
takes place
2 - In the small intestine: Digestive enzymes
accomplish most fat digestion in the small intestine.
There, bile emulsifies fat, making it available for
enzyme action. The enzymes cleave triglycerides into
free fatty acids, glycerol, and monoglycerides
3 - At the intestinal lining: The parts are absorbed by
intestinal villi. Glycerol and short-chain fatty acids
enter directly into the bloodstream
4 - The cells of the intestinal lining convert large lipid
fragments, such as monoglycerides and long-chain
fatty acids, back into triglycerides and combine them
with protein, forming chylomicrons (which is a type of
lipoprotein) that travel in the lymph vessels to the
bloodstream
5 - In the large intestine: A small amount of
cholesterol trapped in fiber exits with the feces
Note: In this diagram, molecules of fatty acids
are shown as large objects, but, in reality,
molecules of fatty acids are too small to see
even with a powerful microscope, while villi are
visible to the naked eye.

Transport of Fats
• Glycerol and shorter-chain fatty acids
• Pass through intestinal lining to bloodstream
• Larger lipids
• Protein carriers
• Travel as passengers in lipoproteins
• Released into lymph
• Chylomicrons

Storing and Using the Body’s Fat
• Body conserves fat molecules
• Fat depots
• Subcutaneous fat layer
• Excess carbohydrate
• Call for energy
• Dismantle stored triglycerides
• Release fatty acids into blood
• Carbohydrate’s role in fat breakdown

Figure 5.10: Glucose to Fat
Glucose is
broken down
into fragments.
The fragments can
provide immediate
energy for the tissues.
Or, if the tissues have
sufficient energy, the
fragments can be
reassembled, not back
into glucose but into
fatty acid chains.

Dietary Fat, Cholesterol, and Health
• Cardiovascular disease
• High intakes of saturated and trans-fatty acids
• Intake of refined carbohydrates
• Not just a “man’s disease”

Recommendations for Lipid Intakes
(Slide 1 of 2)
• Some fat in the diet is essential
• Essential fatty acids
• Linoleic acid and linolenic acid
• Healthy range of fat intakes
• Dietary Reference Intake (D R I)
• Suggests 20 to 35 percent of daily energy
• Fats to consume in small amounts
• U.S. fat intakes
• 35 percent of total energy from fat

Recommendations for Lipid Intakes
(Slide 2 of 2)
• Traditional Mediterranean fat intakes
• Mostly from avocados, extra virgin olive oil, olives, nuts, and seeds
• Cause blood clotting and inflammation
• Too little lipid
• Below 20 percent minimum causes the eater to suffer

Lipid Intake Recommendations for Healthy People
(Slide 1 of 5)
1.Total fata
Dietary Reference Intakes
• An acceptable range of fat intake is estimated at 20 to 35
percent of total calories
2. Saturated fat
American Heart Association
• For adults who would benefit from lowering blood L D L
cholesterol
• Reduce percentage of calories from saturated fat to between 5 and
6 percent

(Slide 2 of 5)
• Keep saturated fat intake low, less than 10 percent of
calories, within the context of an adequate diet
Dietary Guidelines for Americansb
• Consume less than 10 percent of calories per day from
saturated fats
3. Trans fat
American Heart Association
• For adults who would benefit from lowering blood L D L
cholesterol

(Slide 3 of 5)
• Reduce percentage of calories from trans fat
Dietary Guidelines for Americansb
• A healthy eating pattern limits trans fats
4. Polyunsaturated fatty acids
Dietary Reference Intakesc
• Linoleic acid (at 5 to 10 percent of total calories)
• 17 grams/day for young men
• 12 grams/day for young women
• Linolenic acid (at 0.6 to 1.2 percent of total calories)
• 1.6 grams/day for men

(Slide 4 of 5)
• 1.1 grams/day for women
Dietary Guidelines for Americans
• A healthy eating pattern includes oils
5. Cholesterol
• Minimize cholesterol intake within the context of a healthy
diet
aIncludes monounsaturated fatty acids.
bThe Dietary Guidelines for Americans 2015 use the term solid fats to describe sources of saturated and trans-fatty acids. Solid fats include milk
fat, fats of high-fat meats and cheeses, hard margarines, butter, lard, and shortening.
cFor D R I values set for various life stages, see the back of the book, p. A.

Figure 5.11: Sources of Saturated Fats in
the U.S. Diet
Source: U.S. Department of Health and Human Services and U.S. Department of Agriculture, 2015–2020 Dietary
Guidelines for Americans, 8th edition (2015), available at http://health.gov/dietaryguidelines/2015/guidelines/.

Lipoproteins and Heart Disease Risk
(Slide 1 of 3)
• Lipoprotein helps in movement of fats in the body
• Tissues extract fat from chylomicrons
• Liver picks up remnants for reuse
• Types of lipoproteins
• Chylomicrons
• Very-low-density lipoproteins (or V L D L)
• Low-density lipoproteins (or L D L)
• High-density lipoproteins (or H D L)

Figure 5.12: Lipoproteins

(Slide 2 of 3)
• Low-density lipoproteins
(L D L)
• Larger, lighter, and richer in
cholesterol
• Deliver cholesterol to tissues
• High levels trigger
inflammation and heart
disease
• High-density
lipoproteins (H D L)
• Smaller, denser, and
packaged with more protein
• Scavenge excess cholesterol
and other lipids
• High levels oppose heart
disease and vice versa

(Slide 3 of 3)
• Importance of cholesterol testing
• Blood lipid profile tells about a person’s blood cholesterol and the
lipoproteins that carry it
• Two major risk factors for cardiovascular disease (C V D)
• High blood L D L cholesterol
• Low blood H D L cholesterol

What Does Food Cholesterol Have to Do
with Blood Cholesterol?
• Most saturated and trans fats in foods raise harmful
blood cholesterol
• Food cholesterol has little effect on blood cholesterol
• High blood L D L cholesterol is a major indicator of C V D
risk
• Food lipids associated with raising L D L cholesterol
• Saturated fat and trans fat in excess amounts

Recommendations Applied
• Trend: Fewer people in the United States have high
blood cholesterol than in past decades
• More than 25 percent still test too high for L D L
• Lower L D L
• Trim saturated and trans fats from diet
• Raise H D L
• Physical activity provides benefits for heart health

Figure 5.13: Cutting Solid Fats Cuts Calories and
Saturated Fat
© Polara Studios, Inc. (all photos)

Think Fitness: Why Exercise the Body for
the Health of the Heart?
• Physical activity
• Promotes and maintains the health of the heart
• Body’s response to exercise
• Blood lipids shift toward higher H D L cholesterol
• Muscles of the heart and arteries strengthen and circulation
improves
• Larger volume of blood is pumped with each heartbeat, reducing
the heart’s workload
• Body grows leaner, reducing the overall risk of cardiovascular
disease
• Blood glucose regulation is improved, reducing the risk of diabetes

Essential Polyunsaturated Fatty Acids
• Essential fatty acids that cannot be synthesized by our
body
• Linoleic acid and linolenic acid
• Deficiencies
• Cause skin abnormalities and poor wound healing
• Almost unknown among otherwise healthy adults

Omega-6 and Omega-3 Fatty Acid Families
• Linoleic acid is the parent member of:
• Omega-6 fatty acid
• Arachidonic acid: Starting material for making eicosanoids
• Docosahexaenoic acid (D H A) and eicosapentaenoic
acid (E P A) play critical roles in:
• Regulating heart disease
• Cancer prevention
• Promoting healthy tissue functioning by amassing in cell
membranes
• Brain function and vision

Table 5.5: Food Sources of Omega-6 and Omega-3
Fatty Acids (Slide 1 of 2)
Fatty Acid Family Food Sources
Omega-6: Linoleic
acid
Nuts and seeds (such as cashews, walnuts, sunflower
seeds, others)
Poultry fat
Vegetable oils (such as corn, cottonseed, safflower,
sesame, soybean, sunflower); margarines made from these
oils
Omega-3: Linolenic
acida
Nuts and seeds (such as chia seeds, flaxseeds, walnuts,
soybeans)
Vegetable oils (such as canola, flaxseed, soybean, walnut,
wheat germ; liquid or soft margarine made from canola or
soybean oil)
Vegetables (such as soybeans)
Omega-3: E P A and
D H A
Egg, enriched: 75–100 milligrams D H A/egg (or flaxseed-
enriched) and 100–130 milligrams D H A/egg (or fish oil-
enriched)
Human milk

Table 5.5: Food Sources of Omega-6 and Omega-3
Fatty Acids (Slide 2 of 2)
Fatty Acid
Family
Food Sources
Omega-3: E P
A and D H A
Fish and seafood:
Top contributors: (500–1,800 milligrams/3.5 ounces)
Barramundi, Mediterranean seabass (bronzini), herring
(Atlantic and Pacific), mackerel,b oyster (Pacific wild), salmon
(wild and farmed), sardines, shark,b swordfish,b tilefish,b
toothfish (includes Chilean seabass), lake trout (freshwater,
wild, and farmed)
Good contributors: (150–500 milligrams/3.5 ounces) Black
bass, catfish (wild and farmed), clam, crab (Alaskan king),
croakers, flounder, haddock, hake, halibut, oyster (eastern
and farmed), perch, scallop, shrimp (mixed varieties), sole
Other contributors: (25–150 milligrams/3.5 ounces) Cod
(Atlantic and Pacific), grouper, lobster, mahi-mahi, monkfish,
orange roughy,b red snapper, skate, tilapia, triggerfish, tuna,
wahoo
aAlpha-linolenic acid. Also found in the seed oil of the herb evening primrose.
bKing mackerel, orange roughy, shark, swordfish, and tilefish are highest in mercury and should not be consumed by
children or pregnant or lactating women (see the Consumer’s Guide).

Requirements and Sources
• Seafood
• Recommendation: 8 to 12 ounces each week
• Need for sustainable sources
• Fish oil supplements recommended for people with heart
disease
• Supplements of omega-3 fatty acids or fish oil are not
recommended for most people

The Effects of Processing on Unsaturated
Fats (Slide 1 of 2)
• Hydrogenation
• Altering fatty acids in food while processing
• Makes fats resistant to oxidation and helps stay fresher longer
• Unsaturated oils get rancid on oxidation
• Hydrogenated oils
• Have a high smoking point
• Easy to handle and easy to spread

The Effects of Processing on Unsaturated
Fats (Slide 2 of 2)
• Nutrient losses
• Oils lose their unsaturated character and the health benefits that
go with it
• Decrease of vitamin K activity in the body
• Alternatives to hydrogenation
• Adding chemical preservative that will compete for oxygen
• Examples: B H A and B H T listed on snack food labels
• Keeping the product refrigerated

Figure 5.14: Hydrogenation Yields Both Saturated
and Trans-Fatty Acids
Unsaturated fatty acid: Points of unsaturation are places on fatty acid chains where
hydrogen is missing. The bonds that would normally be occupied by hydrogen in a
saturated fatty acid are shared as a somewhat unstable double bond between two
carbons.
Hydrogenated fatty acid (now fully
saturated): When a positively charged
hydrogen is made available to an
unsaturated bond, it readily accepts the
hydrogen and, in the process, becomes
saturated. The fatty acid no longer has
a point of unsaturation.
Trans-fatty acid: The hydrogenation
process also produces some trans-fatty
acids. The trans-fatty acid retains its
double bond but takes a twist instead of
becoming fully saturated. It resembles a
saturated fatty acid both in its shape
and in its effects on health.
aThe usual shape of the double bond structure is known as a cis (pronounced sis) formation.

Trans-Fatty Acids
• Formation of trans-fatty acids
• Hardening of polyunsaturated oils by hydrogenation
• Change in chemical structure
• Health effects
• L D L cholesterol levels raised
• Similarities with saturated fat
• Swapping trans fats for saturated fats
• Trans fat in foods

Fat in the Diet
• Essential fat
• Few teaspoons of raw oil per day and two servings of seafood per
week
• Replace fats instead of adding fats
• Visible versus invisible solid fats
• Added fats
• Majority are invisible fats

Fats in Protein Foods
• Limit intake to 5 to 7 ounces per day
• Choosing low-fat meats
• Ground turkey and chicken are naturally lean
• Commercial processing adds solid fats
• Milk and milk products
• Cream and butter fall in solid fats category
• Grains
• Low in fat when in natural state

Figure 5.15: Calories, Fat, and Saturated Fat in
Cooked Ground Meat Patties
All patties weigh three ounces, cooked. Larger servings will, of course, provide more fat, saturated fat, and
calories than the values listed here.

Figure 5.16: Lipids in Milk and Milk
Products

Defensive Dining (Slide 1 of 2)
• Reading ingredient lists
• In grocery stores
• Choosing seafood
• Choosing among margarines and unsaturated oils
• Adding nuts
• Fat replacers and artificial fats
• Olestra
• “Fat-free” options

Solid Fat Ingredients on Labels (Slide 1 of 2)
• Beef fat
• Butter
• Chicken fat
• Coconut oil
• Cream
• Hydrogenated oil
• Margarine
• Milk fat

Solid Fat Ingredients on Labels (Slide 2 of 2)
• Palm kernel oil; palm oil
• Partially hydrogenated oil
• Pork fat (or lard)
• Shortening

Defensive Dining (Slide 2 of 2)
• Revamp recipes to cut down on solid fats
• Choosing fast foods low in calories and saturated fats to
make fast-food meals healthy
• Change habits
• Small changes can yield big dividends in terms of reducing solid
fat intake

Table 5.7: Solid Fat Replacements (Slide 1 of 5)
Select foods that replace solid fats with polyunsaturated or monounsaturated fats.
Avoid foods that replace fats with refined white flour or added sugars, as these may
present risks of their own. Remember that “light” on a label can refer to color or
texture, so always compare the Nutrition Facts panel with the regular product.
Instead of these solid fats and oils Try choosing these
Regular margarine and butter for
spreading, cooking, or baking
Olive, nut, seed, and other vegetable
oils; reduced-fat, diet, liquid, or spray
margarine; granulated butter replacers;
fruit butters, hummus, nut butters, or
avocado for spreading
Shortening or lard in cooking Nonstick cooking spray, olive oil, or
vegetable oil for frying; applesauce or
oil for baking
Solid fats as seasonings: bacon, bacon
fat, butter; fried onion or greasy crouton
salad toppers
Herbs, lemons, spices, liquid smoke
flavoring, ham-flavored bouillon cubes,
broth, wine; olive oil; olives; toasted nut
or toasted whole-grain crouton toppers

Instead of these milk products/dairy
products
Try choosing these milk
products/dairy products
Whole milk; half and half Fat-free or reduced-fat milk; fat-free half
and half
Regular ricotta cheese; mozzarella
cheese; yogurt or sour cream
Part-skim ricotta or fat-free cottage
cheese; part-skim mozzarella; fat-free
sour cream, “zero” plain Greek-style
yogurta
Regular cheddar, American, or other
cheeses; cream cheese
Low-fat or fat-free cheeses; fat-free or
reduced-fat cream cheese, Neufchatel
cheese
Large amounts of mild cheeses Small amounts of strong-flavored aged
cheeses (such as sharp cheddar; grated
Asiago, Romano, or Parmesan)
Ice cream, mousse, cream custards “Light” ice cream, frozen yogurt, or other
frozen desserts; low-sugar sherbet or
sorbet; skim milk low-sugar puddings

Instead of these protein foods Try choosing these protein foods
Bologna, salami, other sliced sandwich
meats; hot dogs
Low-fat sandwich meats and hot dogs
(95–97% lean, or “light”)
Breakfast sausage or bacon Canadian bacon, lean ham, or soy-
based sausage or bacon-like products
High-fat beef, pork, or lamb; ground beef Leaner cuts trimmed of fat, broiled
salmon or other seafood; ground turkey
breast (98% lean), soy-based “ground
beef” crumbles; legume main dishes
Poultry with skin Skinless poultry
Commercial fish sticks, breaded fried
fish fillets
Plain fish fillets, broiled or rolled in
seasoned whole-wheat breadcrumbs
and pan sautéed in oil

Instead of these grains and desserts Try choosing these grains and
desserts
Chips, such as tortilla or potato;
appetizer crackers
Baked or “light” chips; reduced-fat
crackers and cookies, saltine-type
crackers; nut, seed, or whole-grain
crackers low in saturated and trans fat
Cakes, cookies; doughnuts, pastries,
other desserts
Fresh and dried fruit; whole-grain
muffins, quick breads, or cakes made
with oil (not shortening)
Granola, other cereals with saturated
fat or hydrogenated fat
Cereals low in saturated fat, with no
trans fat (compare the Nutrition Facts
panel information)
Macaroni and cheese Spaghetti and marinara sauce
Ramen-type noodlesb Soba noodles or other whole-grain
noodles cooked in broth, with Asian
seasonings

Instead of these foods Try choosing these foods
Frozen or canned main dishes with more
than 2 or 3 gram saturated fat per serving
Similar foods with less saturated fat per
serving (compare the Nutrition Facts panel
information)
Cream-based, cheese, or “loaded” soups Broth-based, vegetable, or bean soups;
poultry-based, meatless, or other low-fat
chili
aIf the food must be boiled, stabilize the cottage cheese or yogurt with a
small amount of cornstarch or flour.
bRamen noodles are often fried in saturated oils during processing.

Controversy 5: Is Butter Really Back?
The Lipid Guidelines Debate
• Shifting guidelines
• Cut the fat and improve health
• 1960s study: Finland and Crete
• Both countries had high fat intakes (40 percent calorie intake)
• Finland had highest death rate from C V D and Crete had lowest
• Difference: Saturated fats versus olive oil

Dietary Guidelines for Americans 2015
(Slide 1 of 2)
• Saturated fat is a public
health nutrition concern
• Replace with unsaturated fats
• Avoid trans fats
a When replaced by polyunsaturated fat;
the effect of carbohydrate is not clear and
may depend on the type and source of
carbohydrate.
Source: U.S. Department of Agriculture and U.S. Department
of Health and Human Services, Scientific Report of the 2015
Dietary Guidelines Advisory Committee (2015): D-6-12-17,
available at www.health.gov.

Dietary Guidelines for Americans 2015
(Slide 2 of 2)
• 2014 meta-analysis
• Failed to find correlation between saturated fat intake and elevated
C V D risk
• Objections arose from the data
• Power of eating pattern approach helped in:
• Controlling body fatness
• Reducing C V D risk factors

CHAPTER 5 LIPIDS

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