Chapter 5
The Lipids: Fats
and Oils
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A Primer on Fats
• Lipids: a family of compounds that
includes:
 Triglycerides (fats and oils)
 Phospholipids (lecithin)
 Sterols (cholesterol)
• Obvious sources of fat are oil, butter,
margarine, and shortening.
• Other foods contributing fat include
meat, nuts, mayonnaise, salad
dressings, eggs, bacon, gravy, cheese,
ice cream, and whole milk.
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A Primer on Fats
• Fats: lipids that
are solid at room
temperature.
• Oils: lipids that
are liquid at
normal room
temperature.
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Muscles derive
fuel from fat.
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A Primer on Fats
• After eating, the body stores
some fat as an energy reserve.
• The body has unlimited potential
to store fat.
• Excess carbohydrate and protein
can be converted to fat, but they
cannot be made from fat.
• One pound of body fat is worth
3,500 calories.
Within the fat cell, lipid is
stored in a droplet. This
droplet can enlarge, and
the cell membrane will
grow to accommodate its
swollen contents.
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Fat droplet
Cell membrane
Cell nucleus
p. 138
A Primer on Fats
• Satiety: the
feeling of fullness
or satisfaction
that people feel
after meals.
 Fats slow the rate
at which the
stomach empties.
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A Closer View of Fats
• Excess energy from the energyyielding nutrients is stored as fat.
• The fat is first broken into
fragments called fatty acids.
Fatty acids: basic units of fat
composed of chains of carbon atoms
with an acid group at one end and
hydrogen atoms attached all along
their length.
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A Closer View of Fats
About 95 percent of the
lipids in foods and in the
human body are
triglycerides.
• Triglycerides (tryGLISS-er-ides): the
major class of dietary
lipids, including fats and
oils.
• A triglyceride is made
up of three units known
as fatty acids and one
unit called glycerol.
• Glycerol (GLISS-er-all):
an organic compound
that serves as the
backbone for
triglycerides.
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G
l
y
c
e
r
o
l
Fatty acid
+
Fatty acid
Fatty acid
Glycerol + Fatty acids
Triglyceride
p. 139
A Closer View of Fats
Other members of the lipid family are:
•Phospholipid (FOSS-foh-LIP-ids): a lipid similar
to a triglyceride but containing phosphorus; one of
the three main classes of lipids. Examples include:
 Lecithin - a major constituent of cell
membranes, manufactured by the liver and
found in many foods.
•Sterols (STEER-alls): lipids with a structure similar
to that of cholesterol; one of the three main classes
of lipids. Examples include:
 Cholesterol - one of the sterols, manufactured
in the body for a variety of purposes.
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A Closer View of Fats
• Fatty acids differ in the degree of saturation.
• Saturation refers to the chemical structure—
specifically to the number of hydrogens the
fatty acid chain holds.
 Saturated fatty acids are filled to capacity with
hydrogen.
 Unsaturated fatty acids hold an “empty spot” or
point of unsaturation.
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Saturated vs. Unsaturated Fats
• Saturated fatty acid: a fatty acid carrying the maximum
possible number of hydrogen atoms (having no points of
unsaturation). Saturated fats are found in animal foods like
meat, poultry, and full-fat dairy products, and in tropical oils
such as palm and coconut.
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Saturated vs. Unsaturated Fats
• Unsaturated fatty acid: a fatty acid with one or more
points of unsaturation. Unsaturated fats are found in
foods from both plant and animal sources. Unsaturated
fatty acids are further divided into monounsaturated
fatty acids and polyunsaturated fatty acids.
• Monounsaturated fatty acid: a fatty acid containing
one point of unsaturation, found mostly in vegetable oils
such as olive, canola, and peanut.
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Saturated vs. Unsaturated Fats
• Polyunsaturated fatty acid:
(sometimes abbreviated PUFA) a fatty
acid in which two or more points of
unsaturation occur, found in nuts and
vegetable oils such as safflower,
sunflower, and soybean, and in fatty
fish.
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Saturated vs. Unsaturated Fats
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The Essential Fatty Acids
• The human body can synthesize all
fatty acids except:
 Linoleic (lin-oh-LAY-ic) acid, linolenic (lin-ohLEN-ic) acid: polyunsaturated fatty acids, essential
for human beings.
• Essential fatty acid: a fatty acid that cannot
be synthesized in the body in amounts
sufficient to meet physiological need.
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Omega-6 vs. Omega-3 Fatty Acids
• Omega-3 fatty acids,
found in fish oils, offer
a protective effect on
health.
 Interest in fish oils was
first kindled when
someone thought to ask
why the Eskimos of
Greenland, who eat a
diet very high in fat,
have such a low rate of
heart disease.
 Blood clot formation,
inflammation (e.g.
arthritis, asthma),
irregular heart rhythm,
and cancer also seem to
be beneficially affected
by DHA and/ or EPA.
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Something’s Fishy
Eating fish at least two times per week as
part of a balanced diet can:
 Reduce blood clot formation ( heart
attacks and strokes).
 Decrease risk of heart arrhythmias.
 Decrease blood triglycerides.
 Decrease atherosclerotic plaque formation.
 Improve health of arteries.
 Slightly lower blood pressure.
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A comparison of saturated & unsaturated fatty acids in
dietary fats & oils
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Characteristics of Fats in Foods
• Unsaturated fats are more likely to react with
oxygen and become rancid.
• Food manufacturers may alter fats and oils by:
 Hydrogenation (high-droh-gen-AY-shun): the
process of adding hydrogen to unsaturated fat to
make it more solid and more resistant to chemical
change.
 Antioxidant (anti-OX-ih-dant): a compound that
protects other compounds from oxygen by itself
reacting with oxygen.
 Emulsifier: a substance that mixes with both fat
and water and can break fat globules into small
droplets, thereby suspending fat in water.
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Other Members of the Lipid Family
Phospholipids…
• Important components of
cell membranes.
• Can serve as emulsifiers in
the body, joining with
both water and fat.
• Also used in foods such as
margarine, chocolate,
salad dressings, and
frozen desserts to keep
the fats dispersed.
• Widespread in foods.
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Other Members of the Lipid Family
Sterols such as
cholesterol…
Sterols such as cholesterol
have a multiple-ring
structure.
• Incorporated as an integral
part of the structure of cell
membranes.
• Used to make bile for
digestion.
• Used to make sex
hormones (estrogen and
testosterone).
• Made into vitamin D.
• Deposited in the artery
walls, leading to plaque
buildup and heart disease.
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How the Body Handles Fat
•
Lipoproteins (LIP-oh-PRO-teens): clusters
of lipids associated with protein that serve as
transport vehicles for lipids in blood and lymph.
The four main types of lipoproteins are:
1.
2.
3.
4.
Chylomicron (KIGH-loh-MY-cron): a type of
lipoprotein that transports newly digested fat—mostly
triglyceride—from the intestine through lymph and
blood.
VLDL (very-low-density lipoprotein): carries fats
packaged or made by the liver to various tissues in the
body.
LDL (low-density lipoprotein): carries cholesterol
(much of it synthesized in the liver) to body cells. A
high blood cholesterol level usually reflects high LDL.
HDL (high-density lipoprotein): carries cholesterol
in the blood back to the liver for recycling or disposal.
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The composition of lipoproteins
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“Good” vs. “Bad” Cholesterol
• ATHEROSCLEROSIS: As LDL particles
penetrate the walls of the arteries, they
become oxidized-LDL and next are
scavenged by the body’s white blood
cells.
• These foam cells are then deposited into
the lining of the artery wall.
• This process, known as atherosclerosis,
causes plaque deposits to enlarge, artery
walls to lose elasticity, and the passage
through the artery to narrow.
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Atherosclerosis
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Smooth muscle layer
Artery lining
Vessel
opening
Plaque
Normal artery
Early injury triggers
inflammation*
Oxidized LDL
Scavenger +
oxidized LDL
(incorporated
into lining
of artery as
Cholesterol
loaded foam
cell)
Atherosclerosis
White blood cell (scavenger)
LDL +
oxygen
White blood cell
Muscle cells
Accumulation of cholesterolloaded
foam cells—plaque formation
Fig. 5-6, p. 147
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Nourish the Heart
1. Become a savvy supermarket
shopper.
2. Keep blood cholesterol at or below
the recommended levels.
3. Balance energy intake with
energy needs.
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Checking Out the Food Label for
Fat Information
• Total fat refers to all the fat in the food:
saturated, monounsaturated, polyunsaturated,
and trans fat.
• Total fat, saturated fat, trans fat, and
cholesterol information are required on the
label.
• Listing the amount of monounsaturated and
polyunsaturated fats is voluntary.
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Checking
out the
food label
for fat
information
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Fat Can Be Healthy
• Use olive oil and other plant
oils that are rich in
monounsaturated and
polyunsaturated fats.
• Consume more omega-3 fats.
 Consider eating fish twice a week
as part of a balanced diet.
 Plant sources of omega-3 fats
include soybeans, flaxseed,
pecans, and walnuts.
• Consume a diet that is lower
in saturated fat and higher in
complex carbohydrates and
fiber.
 Include more fruits, vegetables,
whole-grain breads, and other
grains and legumes.
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Fat Can Be Healthy
One place to find omega-3 fats is
fish, especially fatty fish like
salmon.
Nuts are rich in
many nutrients and
other beneficial
substances but are
also high in fat.
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Major sources of saturated fat in the U.S. diet
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Legumes and nuts
2%
High-fat meats
(e.g., beef, pork)
High-fat dairy products
(e.g., whole milk, cheese,
ice cream, butter)
20%
Eggs
2%
40%
34%
Other (fruits, vegetables,
grains) 2%
Added fats and oils (e.g.,
shortening, palm oil, coconut
oil, palm kernel oil)
Fig. 5-8, p. 153
Trans Fatty Acid Controversy
• Trans fatty acid: a type of
fatty acid created when an
unsaturated fat is
hydrogenated.
 Found primarily in
margarines, shortenings,
commercial frying fats, and
baked goods.
 Trans fatty acids have been
implicated in research as
culprits in heart disease.
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Trans Fat Controversy
Major sources of trans fatty acids in the U.S. diet
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Animal products
Candy: 1%
Breakfast cereal: 1%
Cakes, cookies, crackers,
pies, bread, etc.
21%
40%
Salad dressing: 3%
Household shortening: 4%
Potato chips, corn
chips, popcorn: 5%
17%
Fried potatoes: 8%
Margarine
Fig. 5-10, p. 154
Trans Fat Controversy
Compare spreads
In 2006, the Food and Drug Administration began
requiring that manufacturers list the trans fat
content on food labels.
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Choose Fats Sensibly
Choose Fats Sensibly…
• Cook and bake with a vegetable oil,
such as canola or olive oil, instead of
butter, shortening, or margarine
whenever possible.
• Try reducing fat in recipes a little at a
time and use nonstick sprays, fat-free
broth or wine in place of butter or
margarine.
• Refrigerate soups and broth, then
skim off the hardened fat.
• Prepare lean meats, trim visible fats,
remove poultry skin and cook meats
so that fats can drain off.
• Use herbs, spices, onions or garlic,
salsa, lemon juice, or mustard instead
of butter, margarine, or oil.
Bake, broil, poach, or steam.
Season with herbs & spices.
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Understanding Fat Substitutes
• Simplesse®: the trade name for a
protein-based, low-calorie artificial
fat, approved by the FDA for use in
foods such as frozen desserts; cannot
be used for frying or baking.
• Olestra: an artificial fat derived from
vegetable oils and sugar combined in
such a way that the body cannot
break them down. Sold under the
brand name Olean®, olestra does not
contribute calories to food.
 It can, however, prevent
absorption of some nutrients.
Thus, the FDA requires all
products made with it to be
fortified with fat-soluble vitamins.
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Diet & Heart Disease
• More than half the people who die
in the U.S. each year die of heart
and blood vessel disease.
• Twin demons that lead to heart
disease are:
1. Atherosclerosis: narrowing of the
arteries caused by plaque build-up.
2. Hypertension: high blood pressure.
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A normal artery provides
open passage for blood
to circulate.
Plaques along an artery
wall narrow the passage
and obstruct blood flow.
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Leading Risk Factors for
Heart Disease
• High LDL blood
cholesterol level
• Low HDL blood
cholesterol level
• High blood pressure
• Cigarette smoking
• Obesity
• Physical inactivity
• Diabetes
• An “atherogenic” diet
(high in saturated
and trans fats, & low
in fruits, vegetables,
legumes, & whole
grains)
• Other risk factors
cannot be changed:
advanced age, male
gender, & family
history
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Relationship between blood cholesterol level & death
rate from heart disease
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Diet and Heart Disease
• Eat a variety of antioxidant-rich fruits and
vegetables. Choose 5 or more daily.
• Choose fat-free or low-fat dairy products, such
as fat-free milk or low-fat or fat-free yogurt.
• Consume abundant legumes of many
varieties, including soybeans, kidney beans,
and lentils.
• Eat a variety of grains, including whole grains.
• Choose skinless poultry, lean meat, and fish,
especially omega-3 fatty acid-rich fish such as
salmon.
• Limit intake of foods high in calories and low
in nutrition.
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Diet and Heart Disease
• Limit foods high in saturated fat, trans fat,
and/or cholesterol, such as full-fat milk
products, fatty meats, tropical oils, partially
hydrogenated vegetable oils and egg yolks.
• Adopt low-fat cooking methods, such as
broiling, baking, steaming, braising, and stirfrying.
• Eat less than 6 grams of salt (sodium chloride)
per day (2400 milligrams of sodium).
• Consume alcohol only in moderation, if at all.
• Have no more than one alcoholic drink per day
(woman) or no more than two drinks per day
(man).
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