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Chapter 5
Lipids
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Student Learning Outcomes 1
5.1 Understand the common properties of lipids.
5.2 List three structural forms of lipids (fats) and the role of
each in our food supply. Distinguish between fatty acids
and triglycerides. Discuss the importance of the essential
fatty acids, as well as the balance between omega-3 and
omega-6 fatty acids, with respect to health.
5.3 Differentiate among food sources of saturated,
monounsaturated, and polyunsaturated fatty acids and
cholesterol.
5.4 Explain how lipids are digested and absorbed.
Student Learning Outcomes 2
5.5 Name the classes of lipoproteins and classify them
according to their functions.
5.6 List the function of lipids, including the roles of
phospholipids and the functions of cholesterol in the body.
5.7 Explain the recommendations for fat intake.
5.8 Characterize the symptoms of cardiovascular disease
and highlight some known risk factors.
5.1 Lipids: Common
Properties
1. What is the common property that all lipid
compounds share?
Lipids: Common Properties
• Diverse group of chemical compounds
• One common property, lipids do not
readily dissolve in water
• Should comprise 20% to 35% of an adult’s
total calorie intake
5.2 Lipids: Triglycerides,
Phospholipids, and Sterols
1. What are four possible structural forms of lipid?
2. In what ways do fatty acids differ from one another?
3. What is difference between a saturated and
unsaturated fatty acid, and between an omega-3 and
an omega-6 fatty acid?
4. Which fatty acids are essential?
5. How do triglycerides differ from phospholipids?
6. What are the main functions of cholesterol in body?
Types of Lipids and Fats
• Types of lipids
– Triglycerides
– Phospholipids
– Sterols (Cholesterol)
• Fats (solid) and oils (liquid)
– 9 kcal /gm
Fatty Acid Structure
Saturated Fatty Acid
Structure
Monounsaturated
Fatty Acid Structure
Polyunsaturated
Fatty Acid Structure
Chemical forms of saturated, monounsaturated, and polyunsaturated fatty acids.
Fatty Acids and Triglycerides
• Found in our body and foods
– In triglycerides, composed of three fatty acids
bonded to glycerol, an alcohol
• Saturated fatty acids, higher in animal fats
– Solid form
• Unsaturated fatty acids, higher in plant foods
– Liquid form
– Cis and Trans
• Fats are composed of both
saturated and unsaturated
Cis and Trans Fatty Acids
Composition of Common Fats / Oils
Chemical
Forms of
Common
Lipids
Essential Fatty Acids
• Must be supplied by the diet to maintain
health
• Omega-3 fatty acid (alpha-linolenic acid)
• Omega-6 fatty acid (linoleic acid)
– immune system function and vision
– help form cell membranes
– produce eicosanoids, which are involved in
practically all important functions in the body
Omega-3 Fatty Acid
• Primarily from nuts, seeds,
fish oil, flax seed oil
• Also found in canola,
walnuts, mussels, crab,
shrimp, and soybean oil
• Recommended intake of
~2 servings of fish per
week
Omega-3 Fatty Acid
(alpha-linolenic acid)
Omega-6 Fatty Acid
• Found in vegetable oils
• Need is about 2-4 tablespoons a day
Omega-6 Fatty Acid
(alpha-linoleic acid)
Essential Fatty Acid Categories
Health-Related Effects 1
• Archidonic acid (Omega-6 )
– Increases blood clotting
– Increases inflammatory responses
Health-Related Effects 2
• DHA, EPA (Omega-3)
– Decrease blood clotting
– Reduce heart attack
– Decrease inflammation
– Excess may cause hemorrhagic stroke
– Other possible uses: lower triglycerides,
rheumatoid arthritis, behavioral disorders
Signs and Symptoms of
Essential Fatty Acids Deficiency
• Flaky, itchy skin
• Diarrhea
• Increased risk of infection
• Stunted growth and reduced wound
healing
Triglycerides
• Most common form of fats and oils
• 3 fatty acids attached to a glycerol
Glycerol + 3 FA’s
Triglyceride +
3 H 20
• diglyceride breakdown product of triglyceride
consisting of two fatty acids bonded to a glycerol
backbone
• monoglyceride breakdown product of a
triglyceride consisting of one fatty acid attached
to a glycerol backbone
Phospholipids
• Built on a glycerol backbone
• Contains phosphorus compound(s)
• Found in body
• Synthesized by the body as needed
• Component of cell membranes
Sterols
• Multi-ringed structure
• Do not have a glycerol backbone
• Cholesterol is a sterol
• Waxy substance
• Do not readily dissolve in water
• Found in animal foods
5.3 Fats and Oils in Foods
1. Which foods are the most fat-dense (>60% total
calories as fat)?
2. Where is cholesterol found in the food supply?
3. Which types of fat are used as emulsifiers, and what is
their function in food?
4. What are some strategies used to produce reducedfat foods?
5. How do fats become rancid, and how can this be
prevented?
6. What happens to unsaturated fats during the process
of hydrogenation?
7. What regulations are in place to educate and protect
the public from trans fats in foods?
Lipids in Foods
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Dairy
Fruits
Grains
Vegetables
Protein
ChooseMyPlate.gov
MyPlate:
Sources of Fats
Grains
Vegetables
Fruits
• Crackers
• French fried
• Fruit pies
• Pasta dishes
potatoes
• Avocadoes
with added fat
Dairy
Protein
• Whole milk
•
Low-fat milk
• Marbled meat
(1%, 2%)
• Bacon
• Some yogurts
• Poultry (skin)
• Many cheeses
• Deep-fat-fried
• Premium ice
meat
• Nuts
cream
0-18 grams per
0-27 grams per
0-11 gram per
0-10 grams per
7-17 grams per
serving
serving
serving
serving
serving
(Avocados):© Ingram Publishing/SuperStock RF; (chicken and fries): © BananaStock / PunchStock RF; (Cheese): © Pixtal/age fotostock RF
Functions of Phospholipids
• Emulsifier
– Bile acids
– Lecithins
– Improves food products
• Found in wheat germ,
peanuts, yolks, soy beans,
organ meat
Emulsifiers
Functions of Cholesterol
• Essential component of cell membrane
• Produced by the liver
• Found only in animal products
• Forms important hormones
– estrogen
– testosterone
– vitamin D
• Precursor to bile acids
Cholesterol
Content of
Foods
Food Sources of Fat
Fat Is Hidden in Some Foods
• Look on the Nutrition Facts labels
• Look on the lists of ingredients
• Control portion size
Fat in Food
• Provides:
– Satiety
– Flavor
– Texture
Low-Fat Diets
• Need time to adjust to taste of low-fat diet
– flavorful fruits, vegetables
• Replace whole milk with 1% or skim
– In time, whole milk will taste too creamy
• Weight control and reduced
risk of chronic disease
Fat-Replacement Strategies for
Reduced-Fat Foods
• Fat commonly replaced with sugar
– Keeps calories close to the same
• Water
– Major component of margarine
• Z-trim®
– Starch derivative that binds with water
• Fiber cellulose
– Maltrin®, Stellar®, Oatrim
• Dairy-Lo®
– Protein globules
Fat Substitutes
• Olestra® or Olean®
(links fatty acid to sucrose)
– Not digested
– FDA approved for fried snack foods
– Fat-soluble vitamins absorption issue
• Salatrim® or Benefat®
– Fat and sucrose
– Not digested and/or absorbed well
Fat Rancidity
• Contains products of decomposed oils
• Breakdown of the C=C bonds by UV light,
and/or O2
• Unpleasant odor and flavor
• Polyunsaturated fatty acid more
susceptible
• Limited shelf life of food products
Prevention of Rancidity
• Hydrogenation
• Addition of vitamin E
• Addition of Butylated
hydroxyanisol (BHA)
and Butylated
hydroxytolune (BHT)
Hydrogenation of Fatty Acids
• Process used to solidify an oil
• Addition of H to C=C double bonds
• Increases shelf life of food product
• Formation of trans fatty acid
– (similar to shape of saturated fatty acid)
• Presents health risk like saturated fats
Hydrogenation
Excessive Trans Fatty
Acid Intake
• Increases risk for
cardiovascular
disease
• Required to be
listed on food
labels
Minimize Intake of Trans Fat
• Limit use of hydrogenated fats
• Limit deep-fried foods
• Limit high-fat baked goods
• Limit use of non-dairy
creamers
Main Sources of Fatty
Acids
5.4 Making Lipids Available
for Body Use
1. What enzyme is responsible for digestion
of triglycerides?
2. What are the end products of fat
digestion?
3. What are the differences between the
absorption of long-versus short-chain fatty
acids?
Digestion
• Enzyme lipase
• Fat-digesting enzyme produced by
salivary glands, stomach, and pancreas
– Acts on triglycerides containing shortand medium-chain fatty acids
Digestion of Fat in
Small Intestine
• Primary site of fat digestion
• Hormone cholecystokinin (CCK)
– Stimulates release of pancreatic lipase
• Bile acid released
– Emulsifies digested fat
• Fat is broken down
– To monoglycerides and fatty acids in watery
digestive juices
Fat Digestion and
Absorption 1
Fat
Digestion
and
Absorpti
on 2
Fat Digestion
and
Absorption
Digestion of Phospholipids
• Enzymes released
– From pancreas
– From cells of the small intestine
• Broken down to
– Glycerol
– Fatty acids
– Remaining parts
Digestion of Cholesterol
• Enzymes released
– From pancreas
• Cholesterol is absorbed
Absorption
• 95% of dietary fat is absorbed
• Diffused into the absorptive cells
• Short- and medium-chain (<12 C) fatty acids
– Are water soluble
– Enter the portal system
• Long-chain fatty acids re-form into triglycerides
– Not water soluble
– Enter the lymphatic system
5.5 Carrying Lipids in the
Bloodstream
1. How do lipids move through the bloodstream?
2. How are dietary fats packaged in the small
intestine and transported?
3. Where are VLDLs made and what do they
contain?
4. Where do the LDLs originate and what is their
destination?
5. Why are HDLs considered “good” cholesterol?
Dietary Fats Are Carried by
Chylomicrons
• Fatty acids re-formed into triglycerides
• Packaged into chylomicrons
• Lipoprotein lipase
– Breaks down triglycerides in the chylomicrons
• Chylomicron remnant
– Delivered to the liver
Carrying Lipids in the
Bloodstream
• Water and oil (fat) do not mix easily
• Unique system of fat transportation is
needed
• Lipoprotein compound in bloodstream
containing a core of lipids with shell
composed of protein, phospholipid, and
cholesterol
– Vehicle used for lipid transport
Structure of a Lipoprotein
Other Lipoproteins Transport Lipids
from the Liver to the Body Cells
• Made primarily by the liver
• Very-Low-Density Lipoprotein
(VLDL), bad
• Low-Density Lipoprotein
(LDL), bad
• High-Density Lipoprotein
(HDL), good
Composition of Lipoproteins
Major Lipoproteins in Blood
Lipoprotein Production and
Function
High-Density Lipoprotein (HDL)
• Synthesized by liver and intestine
• High proportion of protein
• Picks up cholesterol from dying cells and
other sources
• Transfers cholesterol to other lipoproteins
• Transfers cholesterol directly back to the
liver
Benefits of a High HDL level
• Removes cholesterol from the
bloodstream
• HDL may block oxidation of LDL
• Reduces risk of cardiovascular disease
• Pre-menopausal women have higher HDL
Scavenger Cells
• Scavenger WBC removes (oxidized) LDL
from circulation
• Build-up of atherosclerosis plaque on walls
of the blood vessels
• Development of atherosclerosis
• Increased vessel damage caused by
– Smoking, diabetes, hypertension,
homocysteine, high LDL, infection
5.6 Broader Roles for Lipids
in the Body
1. What are functions of triglycerides in
body?
2. Where are phospholipids found in body?
3. What are some compounds made from
cholesterol in body?
Functions of Fatty Acids
• Provide energy
• Efficient storage of energy
• Insulating and protecting body
• Transport fat-soluble vitamins A, D, E, and K
• Phospholipids, become part of cell membrane
• Cholesterol, becomes part of hormones,
estrogen, testosterone, and precursor of active
vitamin D hormone
– Structural component in cells and lipoproteins
Phospholipid and Cell Membranes
Adipose Cell
5.7 Recommendations for
Fat Intake
1. How does percent of calories as fat in
North American diet compare to
recommendations?
2. What is limit for cholesterol intake?
3. What are characteristics of Mediterranean
diet?
Recommendations for Fat Intake
• No RDA but 2010 Dietary Guidelines AMDR 20%
to 35% of calories, 44 to 78 grams
• AHA recommendations
– 20-30% of total kcal from fat
– 7-10% can come from saturated/trans fat
– 200-300 mg cholesterol/day
• Average U.S. intake:
– 33% of total kcal from fat
– 13% of kcal from saturated fat
– 180-320 mg cholesterol/day
Goal of Healthy People 2020
• Reduce
consumption of
saturated fat in
population ages 2
years and older to
9.5% of total calorie
intake
AHA Recommendations
Advice from National Cholesterol
Education Program and Food and
Nutrition Board
• Keep saturated fat, cholesterol, and
trans fat to a minimum
• If diet and exercise are ineffective,
medication intervention recommended
– E.g., Atorvistatin (Lipitor)
– Require physician monitoring
Other Recommendations
• Fat intake can be higher as long as
saturated and trans fatty acid are minimal
• Eat plenty of fruits and vegetables
• Cut down on red meats
• Cut down on simple sugars and refined
carbohydrate
• Promote healthy weight
• Be active
Tips for Avoiding Too Much
Fat, Saturated Fat,
Cholesterol, and Trans Fat
Lipids Concept Map
Nutrition and Your Health
Lipids and
Cardiovascular Disease
Cardiovascular Disease
• Leading cause of death in North America
– 600,000 people die each year
– Annual cost is $108.9 billion each year
• Myocardial infarction
– death of part of heart muscle
– also termed a heart attack
• Cerebrovascular accident
– death of part of brain tissue due typically to a blood
clot
– also termed a stroke
Development of
Cardiovascular Disease
• Plaque
– cholesterol-rich substance deposited in
blood vessels
– contains various white blood cells,
smooth muscle cells, various proteins,
cholesterol, other lipids, and eventually
calcium
The Road to a
Heart Attack
Plaque Buildup in Artery
Walls
View of cholesterol
plaque deposited
inside blood vessel
Risk Factors for
Cardiovascular Disease
• Total blood cholesterol > 200 mg/dl
• Smoking
– Increases clotting
– Increases expression of genetic link
• Hypertension (greater than 139/89)
• Diabetes
– Insulin increases cholesterol synthesis
– Guarantees development of cardiovascular
disease
Other Risk Factors
• Low HDL (< 40 mg/dl)
• Age
• Family history
• Blood triglycerides > 200 mg/dl
• Obesity
– Fat around the waist
– Insulin resistance
• Inactivity
Signs of a Heart Attack
• Intense, prolong chest pain
• Shortness of breath
• Sweating
• Nausea and vomiting
• Dizziness
• Weakness
• Jaw, neck, shoulder pain
• Irregular heartbeat
Medications to Lower
Blood Lipids
• For those who experience a heart attack
– Or have CVD or diabetes
• Heart Attack Risk Calculator
• Medication to lower LDL
– Reduce cholesterol synthesis (Statins,
“Lipitor”)
– Binds to bile acids for elimination
• Medication to lower blood triglycerides
– Reduce triglyceride synthesis
Lowering LDL
• See your doctor to assess for other
conditions
• Reduce dietary saturated fat and
cholesterol
• Increase mono and polyunsaturated fats in
diet
• Increase dietary fiber (soluble)
Lowering Blood Triglycerides
• Is the most diet-responsive blood lipid
• Avoid overeating
• Limit alcohol
• Limit simple sugars
• Small frequent meals
• Include fish in the diet, 2 times per week
Plant Sterols for
Cardiovascular Disease
• Benecol and Take Control margarines
– Plant stanol/sterol esters
– Cholesterol-lowering effects
– Decrease absorption of cholesterol and
lower amount returning via enterohepatic
circulation
– Liver takes up more cholesterol from the
blood
Raising HDL
• Physical activity
• At least 45 min/day,
4 days a week
• Don’t smoke
• Eat regularly
• Eat less total fat
• Moderate intake of alcohol increases HDL
Sorting
Out
One’s
Goals for
Cardiova
scular
Disease
Preventio
n/Treatm
ent
Surgical Treatment for
Cardiovascular Disease
• Two common surgical treatments
– Percutaneous transluminal coronary
angioplasty (PTCA)
• insertion of a balloon catheter into an artery, once
advanced to area of lesion, balloon is expanded to
crush lesion
– Coronary artery bypass graft (CABG)
• removal and use of a saphenous vein (leg), or
mammary vein, sewn into aorta, for bypass