This document provides an overview of lipids, including triglycerides, phospholipids, and sterols. It discusses the three major classes of lipids and their functions in the body. Specifically, it covers the structure and roles of triglycerides, fatty acids, essential fatty acids, trans fats, phospholipids, and cholesterol. It also describes how plant sterols and stanols can help lower blood cholesterol levels. The document is intended to help students learn about the different types of lipids and their importance for health.

1. Because learning changes everything.®
Chapter 6
Lipids: Triglycerides,
Phospholipids, and Sterols
Lecture Outline
HUMAN NUTRITION
Science for Healthy Living
Third Edition
Tammy J. Stephenson, Megan R.
Sanctuary, Caroline W. Passerrello
© 2022 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.

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6.1 Introducing Lipids
Learning Outcomes
1. Identify the three major classes of lipids.
2. Describe major functions of lipids in the body.
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Classes of Lipids
Lipids - a class of nutrients that do not dissolve in water
• This is an important property for understanding their
functions and the way they are transported in the body
Lipids include:
• Triglycerides
• Phospholipids
• Sterols
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Oil and Water Do Not Mix
• Oil is 100% lipid and it does
not dissolve in water
• Oil is less dense than water,
and when a water-oil
mixture is left undisturbed,
the oil rises to and forms a
top layer
McGraw Hill Education
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Major Functions of Lipids
The body uses fats and other lipids to:
• Absorb fat-soluble vitamins and phytochemicals
• Cushion the body against bumps and blows
• Form and maintain cell membranes
• Participate in cell signaling
• Insulate the body against cold temperatures
• Produce steroid hormones
• Provide and store energy (triglycerides)
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Assess Your Progress 6.1
1. List the three major classes of lipids.
2. What are the major functions of lipids in the body?
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6.2 Fatty Acids
Learning Outcomes
1. Distinguish among saturated, monounsaturated, and
polyunsaturated fatty acids.
2. Identify the two essential fatty acids, and explain their
nutritional importance.
3. Describe trans fats, including how they are made and
how they are different from most other fats.
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Fatty Acids1
• Fatty acid - a hydrocarbon chain found in lipids; one end
of the chain forms a carboxylic acid, and one end forms
a methyl group
• Hydrocarbon chain - a chain of carbon atoms bonded
to each other and to hydrogen atoms
• Omega (methyl) end - the end of a fatty acid containing
a methyl (–CH3) group
• Carboxylic acid - an organic molecule with a carboxyl
(–COOH) group
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Fatty Acids2
Short-chain fatty acids have 2 to 4 carbons
Medium-chain fatty acids have 6 to 12 carbons
Long-chain fatty acids have 14 to 24 carbons
Fatty acids are identified by:
• Number of carbon atoms
• The type of bond between carbon atoms in the
hydrocarbon chain
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Saturation1
Saturated fatty acid (SFA) - a fatty acid that has each
carbon atom within the chain filled with hydrogen atoms
Unsaturated fatty acid - a fatty acid that is missing
hydrogen atoms and has one or more double bonds within
the carbon chain
• Monounsaturated fatty acid (MUFA) - fatty acid that has
one double bond within the carbon chain
• Polyunsaturated fatty acid (PUFA) - fatty acid that has
two or more double bonds within the carbon chain
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Fatty Acid Structure
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Saturation2
• Stearic acid - an 18-carbon saturated fatty acid
• Oleic acid - an 18-carbon monounsaturated fatty acid
• Linoleic acid - an 18-carbon polyunsaturated fatty acid
with two double bonds; an essential fatty acid
• Alpha-linolenic acid - an 18-carbon polyunsaturated fatty
acid with three double bonds; an essential fatty acid
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Common Fatty Acids
Fatty Acid Name
Number of
Carbon
Atoms
Number
of Double
Bonds
Saturated Fatty
Acids
Myristic acid 14 0
Palmitic acid 16 0
Stearic acid 18 0
Unsaturated
Fatty Acids
Oleic acid 18 1
Linoleic acid 18 2
Alpha-linolenic
acid
18 3
Arachidonic acid 20 4
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Did You Know? – Fats versus Oils
Both fats and oils have fatty acids, but at room temperature:
• Fats tend to be solid
• Oils tend to be liquid
Foods rich in long-chain SFAs tend to be more solid at room
temperature (For example cream cheese) compared to foods
with high content of unsaturated fatty acids (For example
vegetable oil)
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Omega Fatty Acids
Fatty acids are also identified by the location of double bonds
in the carbon chain
Omega‒3 fatty acid - a type of polyunsaturated fatty acid
with the first double bond at the third carbon from the omega
end of the molecule
• Alpha-linolenic acid
Omega‒6 fatty acid - a type of polyunsaturated fatty acid
with the first double bond at the sixth carbon from the omega
end of the molecule
• Linoleic acid
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Essential Fatty Acids1
Essential fatty acids - fatty acids that must be supplied by
the diet; linoleic and alpha-linolenic acid are essential fatty
acids
The body converts:
• Linoleic acid to arachidonic acid
• Alpha-linolenic acid to eicospentaenoic acid and
docosahexaenoic acid
Arachidonic acid (AA), eicosapentaenoic acid (EPA), and
docosahexaenoic acid (DHA) are all essential fatty acids
that are precursors to eicosanoids
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Essential Fatty Acids2
Eicosanoids - a group of long-chain fatty acids with
hormonelike functions; there are three classes:
• Thromboxanes
• Leukotrienes
• Prostaglandins - a class of eicosanoids that produce a
variety of important effects on the body
Essential fatty acids are necessary in small amounts for good
health
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Essential Fatty Acids3
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Essential Fatty Acids and Health
Essential fatty acids are necessary in small amounts for good
health
• Infants require DHA and EPA for nervous system
development
• Babies do not grow properly if their diet lacks essential
fatty acids
• Signs of essential fatty acid deficiency include:
• Scaly skin
• Hair loss
• Poor wound healing
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Adequate Intake for Essential Fatty Acids
Adequate Intake (AI) for alpha-linolenic acid is:
• 1.6 g/day for men
• 1.1 g/day for women
• Can be met with meals that contain fatty fish such as salmon and
tuna
Adequate Intake (AI) for linoleic acid is:
• 17 g/day for men
• 12 g/day for women
• Can be met with meals containing pecan, almonds and avocado
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What Are Trans Fats?
Most naturally occurring unsaturated fatty acids are cis fatty
acids
• Cis fatty acids have hydrogen atoms of the double-bonded
carbons on same side of hydrocarbon chain
Trans fats are unsaturated fatty acids that have at least one
trans double bond
• Trans fatty acids have hydrogen atoms of the double-
bonded carbons on opposite sides of hydrocarbon chain
• More solid at room temperature than cis fatty acids
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Cis and Trans Double-Bond Arrangements
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Trans Fats in Foods1
Partial hydrogenation - the food manufacturing process that
adds hydrogen atoms to liquid vegetable oil, forming trans
fats
• Oils containing these artificial fats are called partially
hydrogenated oils (PHOs)
Structurally, trans fatty acids resemble saturated ones,
providing the properties of long-chain saturated fatty acids to
foods
• Solid at room temperature
• Can be stored for longer periods because they are less
likely to undergo oxidation
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Trans Fats in Foods2
In 2015, FDA determined that PHOs from processed foods
pose a health risk and the agency banned their use in foods
• Ban went into effect in January, 2020
• Manufacturers can instead preserve fats in foods by
adding:
• Antioxidants
• “Interesterified oil” (an artificial lipid), which may have undesirable
health effects (listed in ingredients as such, or as “fully
hydrogenated” oil)
Some foods naturally contain small amounts of trans fat
• 2020-2025 Dietary Guidelines for Americans recommend
to keep intake as low as possible
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Did You Know? – Palm Oil
Palm oil is made by pressing the flesh of the fruit of the palm
oil tree
Worldwide, over 47 million tons of palm oil are produced
annually
• One of the most commonly consumed oils across the
globe
• Contains about 50% saturated fatty acids and 50%
unsaturated fatty acids
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Fresh Tips – Clarified Butter
Ghee is a type of clarified butter
• Alternative to cooking oil, often used in Indian and Middle
Eastern dishes
• Made from unsalted butter by separating the water and
milk proteins from the butterfat
• Solid at room temperature
• Higher smoke point than butter – does not burn as easily
at high temperatures
• May be made at home or purchased
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Assess Your Progress 6.2
3. What are saturated, monounsaturated, and
polyunsaturated fatty acids?
4. How does an omega‒3 fatty acid differ from an omega‒6
fatty acid?
5. Identify the two essential fatty acids, and describe key
signs of an essential fatty acid deficiency.
6. What structural characteristic distinguishes a trans fatty
acid from a cis fatty acid?
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6.3 Triglycerides
Learning Outcomes
1. Describe the basic structure of a triglyceride.
2. Compare the percentages of saturated,
monounsaturated, and polyunsaturated fatty acids in
animal-derived fats with those in most plant-derived fats.
3. Name two plant oils that are high in saturated fats.
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Triglycerides
Triglyceride - a lipid that has three fatty acids attached to a
three-carbon compound called glycerol
• Comprises 95% of lipids in
food and the human body
Glycerol - a three-carbon
alcohol that forms the
“backbone” of fatty acids
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Mono- and Diglycerides
• Monoglyceride - lipid that has one fatty acid attached to a
three-carbon compound called glycerol
• Diglyceride - lipid that has two fatty acids attached to a
three-carbon compound called glycerol
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Triglycerides in Foods
Most triglycerides contain a mixture of unsaturated and
saturated fatty acids
• One type of fatty acid predominates in a given food
Generally, animal foods contain higher percentages of SFAs
than most plant foods
• The fat in beef and dairy products contains more saturated
than unsaturated fatty acids
• Olive oil is a rich source of MUFAs
• Liquid corn oil contains a greater proportion of unsaturated
than saturated fatty acids
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Fats and Oils
Source: Data from USDA Agricultural Research Service: USDA Food Composition Tables. Updated November 2020. https://www.nal.usda.gov/usda -food-
composition-database. Accessed November 25, 2020.
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Triglycerides and Health
The incidence of CVD, certain cancers and other chromic
diseases is higher in some populations with diets containing
more unsaturated than saturated fat
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Did You Know? – Lard
Lard is pork fat.
• Can be used to make biscuits, pie dough, refried beans
• High in saturated fat (41%), but not as high as butter
(66%)
• Experts recommend limiting intake of saturated fats,
including lard
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Assess Your Progress 6.3
7. Identify at least two foods that are rich sources of
(a) saturated fat, (b) monounsaturated fat, and
(c) polyunsaturated fat.
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6.4 Phospholipids
Learning Outcomes
1. Explain how a phospholipid differs in structure from a
triglyceride.
2. List the key roles of phospholipids in foods and in the
body.
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Phospholipids
Phospholipid - a type of lipid needed to make cell
membranes and for proper functioning of nerve cells;
chemically similar to a triglyceride, except that one of the
fatty acids is replaced by a chemical group that contains
phosphorus
• The chemical group often contains also nitrogen
• Naturally found in foods derived from plants and animals
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Phospholipids are Hydrophilic and Hydrophobic
Phospholipids are partially water soluble because the
phosphorus-containing portion of the molecule is hydrophilic,
but it also has a hydrophobic portion
• Hydrophilic - part of a molecule that attracts water
• Hydrophobic - part of a molecule that avoids water and
attracts lipids
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Lecithin (Phospholipid Molecule)
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Phospholipid Functions
By having both hydrophilic and hydrophobic regions, a
phospholipid can serve as an emulsifier
• Substance that helps water-soluble and water-insoluble
compounds mix with each other
Phospholipids are:
• Major structural components of cell membranes
• Found there forming a double layer
• Enable membrane to be flexible and function
• Needed for normal functioning of nerve cells
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Emulsification
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Phospholipids in Cell Membranes
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Phospholipids in the Body and in Foods
Phospholipid deficiencies are uncommon
• Found in a variety of foods
• Healthy adults synthesize them
Choline - a water-soluble, vitamin-like compound;
component of lecithin
• Used to form the neurotransmitter acetylcholine
Lecithin is the most common phospholipid in food
• Found in abundance in egg yolks, liver, wheat germ,
peanut butter, and soybeans
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Did You Know? – Emulsifiers
Manufacturers may add emulsifiers to foods to keep oily and
watery ingredients from separating during storage
• Processed foods (For example processed cheese foods,
salad dressing, ice cream) often have phospholipids
added as emulsifying agents
• Egg yolk naturally contains phospholipids
• Used to emulsify oil and vinegar when making mayonnaise or
mixing oil and milk in cake batters
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Assess Your Progress 6.4
8. What are the components of a phospholipid?
9. Explain the function of an emulsifier in food preparation
and manufacturing.
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6.5 Cholesterol and Other Sterols
Learning Outcomes
1. Describe key roles of cholesterol in the body.
2. Explain how plant sterols and stanols may lower blood
cholesterol levels.
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Sterols
Sterols – type of lipid that has a more chemically complex
structure than triglycerides and phospholipids.
Cholesterol is the most well-known sterol:
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Cholesterol
Cholesterol - a lipid found in animal foods; precursor for
steroid hormones, bile, and vitamin D
• Essential to health
• Can be made in the body
• Found in abundance in:
• Egg yolk
• Liver
• Meat
• Poultry
• Dairy products made from cream or whole milk
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Plant Sterols and Stanols
Plant sterols and stanols - chemicals found in plants that
are structurally similar to cholesterol
• Compete with cholesterol for intestinal absorption, which
reduces the amount of cholesterol absorbed
• Consumption may lower elevated blood cholesterol levels,
a risk factor for heart disease
• Found in:
• Grains
• Fruits
• Vegetables
• Nuts
• Seeds
• Legumes
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Assess Your Progress 6.5
10. Explain why cholesterol is necessary for health.
11. List three food sources of cholesterol.
12. What effect do plant sterols and stanols have on
cholesterol absorption?
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6.6 Lipid Digestion, Absorption, and Transport
Learning Outcomes
1. Summarize the major steps of lipid digestion and
absorption, and identify the major digestive organs
involved in the process.
2. Describe gallstones and strategies for dietary
management.
3. Identify the function of lipoproteins.
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Lipid Digestion1
Most lipids are completely insoluble in water, complicating
their digestion, absorption and transport
• These processes involve water
Lipases - enzymes that break down lipids
In the mouth, an inactive lipase in saliva mixes with fat-
containing food
• The acidic environment of the stomach activates the
lipase, which begins fat digestion
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Lipid Digestion2
The small intestine is the primary site of lipid digestion; it
secretes hormones in response to fatty chyme:
• Secretin - a hormone that stimulates the liver to produce
bile, and the pancreas to secrete bicarbonate-rich
pancreatic juice (neutralizes stomach acid)
• Cholecystokinin (CCK) - a hormone that stimulates the
gallbladder to release bile and the pancreas to secrete
digestive enzymes, including pancreatic lipase
• Also stimulates liver top produce bile, and the sphincter that
controls the flow of bile into the duodenum to open
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Pancreatic Lipase and Bile Salts
Pancreatic lipase - the digestive enzyme that removes two
fatty acids from each triglyceride molecule
Bile salts - a component of bile; aid in lipid digestion
• Enhance digestion and absorption of lipids by emulsifying
them in the aqueous environment of small intestine,
forming small droplets with greater surface area for better
lipase access
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Triglyceride and Phospholipid Digestion
Triglyceride digestion by pancreatic lipase renders:
• Monoglycerides
• Glycerol
• Fatty acids
A pancreatic phospholipase removes the fatty acid from the
second position of the molecule, yielding:
• Free fatty acids
• Phospholipid remnants
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Lipid Digestion and Absorption1
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Lipid Digestion and Absorption2
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Lipid Absorption1
The majority of lipid absorption (including undigested
cholesterol) occurs in the small intestine
Short- and medium-chain fatty acids diffuse into the
absorptive cells of the villi
• Enter the capillary network (bloodstream)
Long-chain fatty acid absorption requires additional steps
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Lipid Absorption2
Long-chain fatty acids, bile, cholesterol, and fat-soluble
vitamins pack together into micelles
• Micelle - water-soluble, spherical lipid cluster; bile salts
create a shell around each cluster, allowing for the
structure to be suspended in watery digestive juices
• When micelles come close to villi, their contents diffuse
into absorptive cells (enterocytes)
Fat malabsorption - impaired fat absorption; symptoms
include diarrhea, fatty stools, and rapid weight loss
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Lipid Transportation
After absorption, fatty acids, glycerol, monoglycerides, and
phospholipid fragments are reassembled into triglycerides
and phospholipids inside enterocytes
Cholesterol and the reassembled triglycerides are coated
with a thin layer of protein, phospholipids, and cholesterol to
form chylomicrons
• Chylomicron - a type of lipoprotein formed in enterocytes
to transport lipids away from the GI tract
• Chylomicrons enter into the lacteals
Lipoproteins - water-soluble structures that transport lipids
through the bloodstream
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Lipoproteins: A Chylomicron
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Transportation of Chylomicrons
The lymphatic system transports chylomicrons to the thoracic
duct
• Enter the bloodstream through the left subclavian vein
• Circulate through the body
• Lipoprotein lipase (LPL) - an enzyme in capillary walls,
breaks down triglycerides
• Nearby cells pick up fatty acids and glycerol to use for energy
• 10-12 hours after a meal, most chylomicrons are reduced
to cholesterol-rich remnants
• Cleared from bloodstream by the liver
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Journey into the General Circulation
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Summary of Lipid Digestion and Absorption
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Lipoproteins1
The body makes additional lipoproteins for lipid transport
• Each type carries different proportions of protein,
cholesterol, triglycerides, and phospholipids
• Their density varies accordingly
Very-low-density lipoprotein (VLDL) - a lipoprotein made in
the liver; carries much of the triglycerides in the bloodstream
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Lipoproteins2
Low-density lipoprotein (LDL) - a lipoprotein that carries
cholesterol into tissues
• Elevated LDL is linked to increased risk of CVD
High-density lipoprotein (HDL) - a lipoprotein that
transports cholesterol away from tissues and to the liver,
where it can be eliminated
• Low HDL is linked to increased risk for CVD
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Major Lipoproteins
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Enterohepatic Circulation of Bile
Enterohepatic circulation -
process that recycles bile salts in
the body
• About 98% of bile salts are
reabsorbed in ileum, travel in
bloodstream to liver, where
they are incorporated into new
bile
• Plants contain substances (For example soluble fiber) that
interfere with cholesterol and bile absorption, helping
reduce blood cholesterol levels
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Gallstones1
Gallstones - hard particles that can accumulate in the
gallbladder or become lodged in one of the ducts carrying
bile from the gallbladder to the small intestine
Cholecystectomy - surgery to remove a diseased
gallbladder
Steatorrhea - presence of lipid in the stool
• Can occur if gallbladder is diseased or removed, as fats
digestion is less efficient
• Eat smaller, more frequent meals and avoid high-fat meals
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Gallstones2
Clinical Photography, Central Manchester University Hospitals NHS Foundation Trust, UK/Science
Source
Gallstones can form in the
gallbladder
The stones usually consist
of cholesterol
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Lipid Storage Diseases
Lipid storage diseases (singular lipidosis, plural lipidoses)
are genetic conditions that cause lipid accumulation in cells,
damaging tissues
• Some signs of lipidoses include an enlarged spleen or
liver, swollen abdomen, skeletal disorders, and swollen
lymph nodes
Gaucher disease - the most common lipid storage disease;
caused by a deficiency of an enzyme involved in lipid
metabolism
• Lipids accumulate in bone marrow and some organs, and
can be fatal
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Assess Your Progress 6.6
13. Describe what happens to the fat in a piece of fried
chicken as it undergoes digestion and absorption;
include the roles of bile, CCK, pancreatic lipase, villi, and
micelles.
14. Compare the composition of a chylomicron, VLDL, LDL,
and HDL.
15. Explain the relationship between fat malabsorption and
steatorrhea.
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6.7 Lipid Consumption Patterns
Learning Outcomes
1. Summarize current lipid consumption patterns in the
United States.
2. List total dietary fat, saturated fat, trans fat, and
cholesterol intake recommendations.
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Lipid Consumption Patterns1
In 2017-2018 Americans consumed on average about 37%
of their total daily energy from fat
• AMDR for fat is 20 to 35%
According to the 2020-2025 Dietary Guidelines for
Americans, adults should emphasize foods that are rich in
PUFAs and MUFAs
• Fish
• Nuts
• Vegetable oils
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Lipid Consumption Patterns2
In 2017-2018 Americans consumed about 12% of their total
daily energy from saturated fat, 12% from monounsaturated
fat, and 9% from polyunsaturated fats
• Average cholesterol consumption was 321 mg/day for
males and 245 mg/day for females
According to the 2020-2025 Dietary Guidelines for
Americans, adults should:
• consume less that 10% of their total calories from
saturated fatty acids
• limit trans fat and cholesterol intakes
AMDRs have been established for the essential fatty acids
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Dietary Fat and Cholesterol Recommendations
• Total fat: 20 to 35% of total calories (45 to 75 g total fat for
a 2,000-kcal diet)
• Saturated fat: Less than 10% of total calories (22 g
saturated fat for a 2,000-kcal diet)
• Linoleic acid: 5-10% of total calories (11-22 g linoleic acid
for a 2,000-kcal diet)
• Alpha-linolenic acid: 0.6-1.2% of total calories (1-3 g
alpha-linolenic acid for a 2,000-kcal diet)
• Cholesterol: As little as possible while consuming a
healthy diet
• Trans fat: Keep intake as low as possible
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Assess Your Progress 6.7
16. What percentage of total energy intake does fat
contribute in the “average” American’s diet?
17. According to the 2020-2025 Dietary Guidelines for
Americans, how much saturated fat, cholesterol, and
trans fat should an adult consume?
18. Calculate how many grams of total fat, saturated fat,
linoleic acid, and alpha-linolenic acid an adult should
consume who is eating 2,300 kcal daily.
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6.8 Lipids and Cardiovascular Disease
Learning Outcomes
1. Explain the process and health effects of atherosclerosis.
2. List at least six risk factors for developing cardiovascular
disease.
3. Distinguish between high-density lipoprotein (HDL) and
low-density lipoprotein (LDL).
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Cardiovascular Disease in the USA
According to the American Heart Association, in 2019, 121.5
million Americans were living with one or more forms of CVD
In 2017, heart disease and stroke together accounted for
28% of all deaths
People often establish poor lifestyle practices early in life
• Changing these practices at any age can reduce their
chances of developing CVD
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From Atherosclerosis to Cardiovascular Disease
• Cardiovascular disease (CVD) - a group of diseases that
affect the heart and blood vessels; includes coronary
artery disease, stroke, and disease of the blood vessels
• Atherosclerosis - a long-term disease process in which
plague builds up inside arterial walls
• Arteriosclerosis - a condition that results from
atherosclerosis and is characterized by loss of arterial
flexibility
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How Atherosclerosis Develops 1
When the arterial lining is injured (For example by oxidation,
infection, nutrient deficiency), a cascade of events begins,
resulting in atherosclerosis
• Injured arterial lining becomes inflamed due to immune
response
• WBCs contribute to lesions on blood vessel walls as they
attempt to repair damage
• Enlarged WBCs get trapped in artery wall, contributing to
formation of artery plaque
• Arterial plaque, a fatty buildup in the artery
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How Atherosclerosis Develops 2
• Arterial plaque narrows the artery
• Interferes with circulation
• May block its entire opening (lumen)
• Arterial plaque roughens the normally smooth arterial
endothelial surface
• Blood flow to the area supplied by the artery is slowed down
• Blood clots are more likely to form
• When a plaque ruptures, its repair also involves clot formation
• Blood clots can be life threatening
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Atherosclerosis
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Healthy and Atherosclerotic Arteries
(a) Al Telser/McGraw Hill; (b) Image Source/Getty Images
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Myocardial Infarction, Stroke, and Gangrene
Thrombus - fixed bunch of clots that remain in place and
disrupt blood flow
• Partially closes off artery’s lumen
Myocardial infarction - heart attack; occurs when a
thrombus completely blocks blood flow to the heart muscle
and the muscle dies
• If severe, sudden death can occur
Stroke - occurs when a clot blocks an artery in the brain;
brain cells that are nourished by the vessel die
When artery to a limb is blocked, the tissue dies, causing
gangrene; may require amputation to avoid infection
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Embolus Formation
• Embolus - a thrombus
or part of a plaque that
breaks free and travels
through the bloodstream
• Can create same serious
consequences as a
stationary thrombus
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Atherosclerosis in the Carotid Arteries
• The carotid arteries convey
blood to the brain
• Atherosclerosis in these
arteries can reduce blood
flow to the brain and
increase the risk of stroke
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CVD: Major Risk Factors
Nonmodifiable Risk Factors
• Family history of CVD
(especially before 60 years
of age)
• Advanced age
• Male sex
• Race/ethnic background
Modifiable Risk Factors
• Diabetes mellitus
• Elevated blood cholesterol
(especially LDL
cholesterol)
• Excess body fat
• Hypertension
• Physical inactivity
• Tobacco use or exposure
to tobacco smoke
• Unhealthy diet
• Untreated sleep apnea
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Did You Know? – Sleep-Disordered Breathing (SDB)
Conditions
SDB conditions, including sleep apnea, are common among
overweight and obese people
A person with sleep apnea stops breathing while asleep
• Wakes up repeatedly
• Does not feel refreshed after sleeping
College and professional football players are at high risk for
SDB
SDB sufferers have an increased risk for chronic disease,
including heart disease
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Homocysteine and Cardiovascular Disease
Homocysteine - an amino acid that may play a role in the
development of atherosclerosis
• Not found in human proteins
• Toxic by-product of protein metabolism
• Cells use vitamins B-6, B-12 and folate to eliminate it
Homocysteinuria - a group of conditions caused by gene
mutations that cause homocysteine to accumulate in the
blood
• May injure arterial walls
• Lead to increased risk of developing CVD
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Lipoproteins and Atherosclerosis
Lipoproteins play major roles in the development of
atherosclerosis
• HDL is “good” cholesterol, conveys lipids away from
tissues and to the liver, where they can be processed and
eliminated
• LDL is “bad” cholesterol, conveys lipid from the liver to
body tissues
• Small, dense forms of LDL contribute more to atherosclerosis
Oxidized LDL - LDL that has been damaged by free radicals
• May lead to atherosclerosis
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Role of HDL and LDL in Lipid Transport
Access the text alternative for slide images.
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VLDL Carries More Triglycerides than Cholesterol
VLDLs shuttle lipids to adipose cells, which remove
triglycerides from them
• Adipose (fat) cells store triglycerides
As blood concentrations of triglycerides increase, HDL levels
decrease
• May contribute to CVD
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COVID-19 and Heart Disease
• Stroke survivors and those with heart disease, including
HBP and congenital heart defects, are at increased risk for
complications from COVID-19
• As of January 2021, the American Heart Association
(AHA) has committed $2.5 million to research the
relationship between COVID-19 and CVD
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Assessing Risk of Atherosclerosis1
Lipoprotein profile - a series of blood tests to evaluate total
cholesterol, HDL cholesterol, LDL cholesterol, and
triglyceride levels
• Helps determine a person’s risk for developing
atherosclerosis
According to the AHA, the desirable range for total blood
cholesterol is < 200 mg/dL
• In the USA, 95 million adults have total cholesterol levels >
200 mg/dL, and 29 million > 240 mg/dL
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Assessing Risk of Atherosclerosis2
The ratio of LDL and HDL are more critical risk factors than
total cholesterol
• About one in three U.S. adults has high LDL cholesterol
The amount of lipids in serum or plasma, rather than in whole
blood, is usually measured
Serum – the liquid portion of blood that has had the cells and
clotting factors removed
Plasma – the liquid portion of blood that has had the cells
removed; contains clotting factors
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Classification of Fasting Blood Lipid Levels
Total Cholesterol (mg/dl) Classification
< 200 Desirable
200-239 Borderline high
≥ 240 High
LDL Cholesterol (mg/dl) Classification
< 100 Optimal
100-129 Near optimal/Above optimal
130-159 Borderline high
160-189 High
≥ 190 Very high
HDL Cholesterol (mg/dl) Classification
< 40 (for men); < 50 (for women) Low
≥ 40 (for men); ≥ 50 (for women) Desirable
Triglycerides (mg/dl) Classification
< 150 Normal
150-199 Borderline high
≥ 200 High
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C-Reactive Protein (CRP)
• The development of CVD involves chronic inflammation
• High-sensitivity C-reactive protein (hs-CRP) - a protein
produced primarily by the liver in response to
inflammation; a marker of CVD
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Did You Know? – Coronary Calcium
Cigarette smoking and elevated total cholesterol levels in
early adulthood are associated with the formation of coronary
calcium (calcium deposits in arteries of the heart)
• High amounts of coronary calcium are associated with
increased risk of atherosclerosis
Aortic valve calcification can be detected by
echocardiography or computed tomography (CT) scans
• CT scanning involves exposure to ionizing radiation, and
physicians generally reserve its use for other diagnostic
purposes
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Assess Your Progress 6.8(1)
19. Discuss the series of physiological changes that occur in
arteries and contribute to the development of CVD.
20. What are the recommendations concerning healthy
blood lipoprotein levels?
21. List at least three major risk factors for developing CVD
that are nonmodifiable and at least five that are
modifiable.
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Assess Your Progress 6.8(2)
22. Discuss the possible connection between elevated blood
homocysteine levels and CVD.
23. Bernard’s total blood cholesterol level is 195 mg/dL, and
his HDL cholesterol level is 62 mg/dL. Based on this
information, does Bernard have a high risk or low risk of
developing CVD? Explain your answer.
24. What is “hs-CRP”? How does it relate to the risk of
developing CVD?
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6.9 Reducing Risk of Atherosclerosis: Dietary Changes
Learning Outcomes
1. Explain dietary factors that can reduce risk for developing
atherosclerosis.
2. Summarize lifestyle factors that can reduce risk for
developing atherosclerosis.
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Dietary Changes1
SFAs impair liver cell function, and thus less cholesterol gets
removed from the bloodstream
• Most SFAs increase total cholesterol by raising both HDL
and LDL cholesterol
MUFAs generally lower blood LDL cholesterol without
reducing HDL cholesterol
• While PUFAs may also reduce HDL cholesterol in some
individuals, they tend to be healthful because they do not
promote atherosclerosis
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Dietary Changes2
To reduce the risk of developing CVD, the 2020-2025 Dietary
Guidelines for Americans and AHA recommend:
• Limit saturated fat intake to less than 10% of total energy
• By replacing foods that are rich sources of long-chain saturated fat
with foods that contain greater percentages of unsaturated fat
• Limit trans fat intake as much as possible as trans fats
also raise blood cholesterol levels
• By eating fewer solid fats, especially foods made with partially
hydrogenated oils, such as stick margarine
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Did You Know? – Coconut Oil
Coconuts and coconut oil are important components of diets
in many parts of the world
• Coconut oil has been marketed in the United States as a
"heart-healthy" oil
Research suggests that consumption of coconut oil raises
blood cholesterol levels to a greater extent than unsaturated
plant oils
• Coconut oil may be a heart-healthy alternative to saturated
fat sources, such as butter, but should be consumed in
moderation due to its potential to raise total and LDL blood
cholesterol levels
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Omega-6 and Omega-3 Fats
The typical American consumes far more omega-6 than
omega-3 fatty acids
• The essential omega-6 fatty acid, linoleic acid, is found in
vegetable oils used for frying and for making margarines
and salad dressings
• Eating foods that supply omega-3 fatty acids reduces risk
of developing heart disease more than eating foods that
supply omega-6 fatty acids
• Omega-3 fatty acid supplements in doses higher than 3 g/day may
interfere with blood clotting and increase stroke risk
• Consumers should consult healthcare provider before taking fish oil
supplements
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Possible Health Benefits of Omega-3 Fatty Acids
Omega-3 Fats May Reduce the Risk of Developing
• Alzheimer’s disease
• Arthritis
• Certain cancers
• Dental disease
• Depression, including postpartum depression
• Heart disease
• Preterm birth
Omega-3 Fats May Improve
• Alzheimer’s disease
• Cognitive development in infants
• Rheumatoid arthritis symptoms
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Rich Food Sources of Omega-3 Fats
Fish/Shellfish (DHA and EPA)
Herring, salmon, sablefish,
anchovies, tuna, bluefish, sardines,
catfish, striped bass, mackerel, trout,
halibut, pollock, flounder, shrimp,
mussels, crab
Oils
Flaxseed, walnut, canola, soybean
Nuts and Seeds
Walnuts, flaxseeds
Other
Algae
The 2020-2025
Dietary Guidelines
for Americans
recommends
consumption of at
least 8 ounces of
seafood (fish and
shellfish) a week.
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Dietary Cholesterol
Many foods derived from animals are high in cholesterol and
saturated fat
• Limiting consumption may help reduce dietary cholesterol
and saturated fat intakes
Scientific evidence suggests that dietary cholesterol does not
have as much effect on blood cholesterol levels as dietary
saturated fat
• The liver synthesizes less cholesterol when dietary
cholesterol intake is higher
• Eating large amounts of saturated fat increases the liver’s
cholesterol production
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Sustainability and Your Diet
Consumption of grass-fed beef has increased in the USA due
to awareness of issues related to sustainability, animal
welfare, and potential health benefits
• Compared to grain-fed beef, grass-fed beef often has a
lower total fat content with less saturated fat and more
omega-3 fatty acids
• But factors such as breed, season, forage type, and
location impact the fatty acid composition of beef
• It is important to read nutrition labels carefully
Consuming locally produced, grass-fed beef can be a
sustainable choice that supports local farmers and reduces
the environmental impact
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Food Selection and Preparation
Certain practices help reduce intake of dietary fats,
especially unhealthy ones
• Limit processed and cured meats
• Use cooking methods that do not add fat
• After cooking, avoid eating the visible fat that remains
• Trim away or drain from pan the fat from meat
• Do not use pan drippings to make sauces or gravies
• Beware of foods high in fat
• Cream cheese, margarine, fried foods, salad dressings, bacon,
sausage, hot dogs, luncheon meats, hard cheeses
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Other Dietary Modifications
Other dietary changes may reduce risk of developing CVD
• Eating foods high in fiber, especially soluble fiber
• Reducing intake of refined carbohydrates: candy, pastries,
sugar-sweetened soft drinks
• Consuming less alcohol
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Fresh Tips – Reducing Saturated and Trans Fat Intakes
Read the Nutrition Facts panel and the ingredient list on the
label when choosing processed foods
• Avoid products that include interesterified (fully
hydrogenated) oil, partially hydrogenated fat, or shortening
Eat fewer commercially prepared baked goods, snack foods,
and fried fast-food items
Buy plain popcorn, and pop the kernels using a small amount
of hot oil in a covered saucepan
Consume commercial frostings in moderation
Use natural peanut or almond butter with just peanuts or
almonds on the ingredient list
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Weight Loss and Physical Activity
Engaging in moderate-intensity physical activity at least 150
minutes a week and consuming moderate amounts of a variety of
healthy foods can help achieve and maintain healthy body weights
• Taking these steps can also reduce blood LDL and triglyceride
levels and raise blood HDL levels
If lifestyle changes do not work:
• Statins - class of prescription drugs that interfere with liver’s
metabolism of cholesterol, reducing LDL and triglycerides
• Zetia® is a drug that inhibits intestinal absorption of cholesterol,
lowering LDL levels; questions about its safety have been
raised
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Did You Know? – Coffee Beverages and Fat
To reduce fat intake from coffee beverages, select low-fat
options and add only small amounts of creamer
The calorie, total fat, and saturated fat content for a 2-
tablespoon serving of commonly added ingredients are:
• Light cream (59 kcal, 6 g total fat, 4 g saturated fat)
• Coffee creamer, liquid (41 kcal, 3 g total fat, 1 g saturated
fat)
• Half-and-half (39 kcal, 3 g total fat, 2 g saturated fat)
• Whole milk (18 kcal, 1 g total fat, 1 g saturated fat)
• 2% milk (15 kcal, 1 g total fat, less than 1 g saturated fat)
• Soy milk (13 kcal, 0 g total fat, 0 g saturated fat)
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Assess Your Progress 6.9
25. Suggest at least four ways people can reduce their
intakes of saturated fats and increase their intakes of
unsaturated fats.
26. List at least two strategies for reducing trans fat intake.
27. Describe four health benefits of omega-3 fatty acid
consumption.
28. List five rich food sources of omega-3 fatty acids.
29. Describe how prescription medications may improve
blood lipid levels.
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Case Study1
Lipids and heart health
Although she was overweight, 45-year-old Samantha was
surprised to learn at her last doctor’s appointment that she
had high blood pressure. Additionally, her lab values
indicated that some of her blood lipids were not within the
desirable range.
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Case Study2
Her total cholesterol was 230 mg/dL; her LDL cholesterol
was 140 mg/dL; her HDL cholesterol was 35 mg/dL; and her
triglycerides were 90 mg/dL. The physician told Samantha
she had a high risk for developing heart disease. As a result
of her physician’s advice, Samantha is ready to make
lifestyle changes to lower her risk of heart disease.
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Case Study3
1. What are normal blood lipid levels for adult females?
2. Explain the differences between HDL cholesterol and LDL
cholesterol.
3. Describe how blood lipid concentrations contribute to the
development of heart disease.
4. List five dietary recommendations to help Samantha
lower her risk of developing heart disease.
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