Transcript Chapter 6

Lecture
Outline
Chapter 6
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fats and Other Lipids
Chapter 6
Insert photo of
fries and dip
from chapter
opener
Chapter Learning Outcomes
1. Distinguish various lipids and identify at least
one physiological role of each type of lipid.
2. Identify major food sources of lipids, including
trans fatty acids.
3. Explain the process of atherosclerosis and list at
least 6 risk factors of cardiovascular disease.
4. Distinguish HDL cholesterol from LDL
cholesterol.
5. Identify major dietary sources of omega-3 fatty
acids.
6. List dietary and other lifestyle actions that can
reduce the risk of cardiovascular disease.
Quiz Yourself
True or False

1. To lose weight, use regular, stick margarine
instead of butter because it has 25% fewer
kilocalories per teaspoon. T F
2. Egg yolks are a rich source of cholesterol. T F
3. Taking too many fish oil supplements may be
harmful to health. T F
4. On average, Americans consume 60% of their
calories from fat. T F
5. Increasing your intake of trans fats can reduce
your risk of heart disease. T F
How Did You Do?

1. False Regular stick margarine has about the
same kcal/teaspoon as butter.
2. True Egg yolks are a rich source of cholesterol.
3. True Taking too many fish oil supplements may
be harmful to health.
4. False The average American consumes about
1/3 of his/her daily energy intake from fat.
5. False Increasing your intake of trans fats may
increase your risk of heart disease.
Understanding Lipids
Lipids include:
- Fatty acids
- Triglycerides
- Phospholipids
- Cholesterol
• Lipids are
– insoluble in water
– less dense than water
“Oil and
Water Don’t
Mix”
Since oil is less
dense than water,
it floats on top.
• Insert bottle of oil
and vinegar from
page 145
Fatty Acids
Fatty acids contain a hydrocarbon chain (carbon and
hydrogen atoms) with a methyl group (CH3) at one end
and an acid group (COOH) at the other.
Insert Figure 6.1
Fatty acids vary in their number of carbons:
Short chain fatty acids — 2 to 4 carbons
Medium chain fatty acids — 6 to 12 carbons
Long chain fatty acids –- 14 to 24 carbons
Saturation
Fatty acids also vary by saturation.
• Saturated – each carbon atom within the chain
holds 2 hydrogen atoms.
• Unsaturated – one or more carbon atoms within
the chain lack 2 hydrogen atoms, and as a result,
the molecule has 1 or more double bonds.
Insert figure 6.1
Unsaturated Fatty acids
Insert figure 6.1
Essential Fatty Acids
Insert figure 6.2
The 2 essential fatty acids are:
1) Alpha-linolenic acid 2) Linoleic acid
Benefits of Essential Fatty Acids
• Precursors of prostaglandins
Hormone-like substances formed from
EPA, DHA, and arachidonic acid
• Effects of prostaglandins:
– Stimulate uterine contractions
– Regulate blood pressure
– Promote immune system response
Trans Fats
What are trans fats?
Unsaturated fats with at least 1 trans
double bond rather than the more
common cis bond
Insert figure 6.3 a from page 148
Hydrogenation
Hydrogenation:
Process that adds hydrogen atoms to liquid
vegetable oils
Partial hydrogenation:
– Not all double bonds are hydrogenated.
– Natural cis double bonds convert to the
unhealthy trans form.
Trans Fats and Health
• Used in many processed foods
• High amounts of trans fats in diet
increase heart disease risk by raising
blood cholesterol levels.
• FDA requires amount of trans fat
displayed on Nutrition Facts panel.
Triglycerides
• Composed of 3 fatty
acids attached to a
glycerol “backbone”
• ~ 95% of lipids in the
body and foods is in
the form of
triglycerides.
Insert figure 6.4
Approximate Percentages of Saturated
and Unsaturated Fatty Acids in
Common Fats and Oils
Insert Table 6.1
Insert figure 6.5
Phospholipids
 Chemically similar to a
triglyceride, except 1 fatty
acid is replaced by a
compound containing
phosphorus and nitrogen
groups
Lecithin - The main
phospholipid in foods such
as egg yolks, liver, wheat
germ, peanut butter, and soy
Hydrophobic/
Hydrophilic
Phospholipids act as
emulsifiers, because
they have
hydrophobic and
hydrophilic regions.
• Hydrophobic region
– Attracts lipids and
avoids water
• Hydrophilic region
– Attracts water and
avoids lipids
Insert figure 6.5
Emulsification
Insert Figure 6.6
Cholesterol
Cholesterol: sterol containing carbon,
hydrogen, and oxygen atoms arranged in a
complex
ring-like structure
Insert figure 6.7
Functions of Cholesterol
The body uses cholesterol to make
various substances, including:
– Vitamin D
– Steroid hormones
• Estrogen
• Testosterone
– Bile
Cholesterol Content of Some
Common Foods
Insert Table 6.2
Digesting Triglycerides
Insert figure 6.8
In the duodenum,
pancreatic lipase
digests triglycerides,
forming primarily:
- Monoglycerides
- Free fatty acids
Bile
Bile — made in the
liver and stored in
the gallbladder
– Bile contains bile
salts.
Emulsification occurs in
the small intestine, as
fat droplets are
coated with bile salts.
Insert Figure 6.9
Chylomicron Formation
Insert figure 6.9
Journey Into General
Circulation
Insert figure 6.10
Overview of Lipid Digestion
1. Stomach — minor fat
digestion occurs
2. Liver — produces bile that
helps emulsify fat (bile is
stored in gallbladder)
3. Pancreas — secretes
lipase into small intestine
4. Small intestine — main
site for lipid digestion and
absorption
5. Anus — less than 5% of
undigested fat is
excreted in feces
Insert figure 6.11
Recycling Bile Salts
Enterohepatic
Circulation
Liver: uses cholesterol to
make bile salts
Gallbladder: stores
bile before release into
small intestine
Small intestine: site
where bile emulsifies
fat.
Portal vein: returns bile
salts to liver, where the
compounds are
recycled
Insert Figure 6.12
Using Triglycerides for Energy
Adipose cell — stores a large
triglyceride droplet
Adipose cells can break down
triglycerides into fatty acid and
glycerol molecules, and release them
into blood stream.
Other cells remove fatty acids from
circulation and use them for energy.
Liver can convert glycerol to glucose—
another energy source.
Triglycerides provide 9 kcal/g
(carbohydrate and protein provide 4
kcal/g)
Insert Figure 6.13
Americans’ Lipid Consumption Patterns
and Recommendations
Average Annual Fat Intake
1909 – 1919 - 42 lbs/person
1990 – 1999 - 70 lbs/person
Acceptable Macronutrient Distribution Range
20 to 35% of total calories
U.S. Dietary Guidelines 2005
< 20 to 35% of total calories
< 10% of calories from saturated fats
< 300 mg cholesterol daily
Avoid foods with trans fatty acids
Understanding Nutritional
Labeling: Lipids
Lipid information required
on Nutrition Facts panel:
- Total kilocalories from fat
- Total fat (g)
- Saturated fat (g)
- Trans fat (g)
- Cholesterol (mg)
Panel may include:
- Polyunsaturated (g)
- Monounsaturated (g)
Insert Fig. 6.14
Why “Grams of Fat” May
Not Add Up
2g
Total Fat
Saturated Fat
Trans Fat
Poly. Fat
Mono. Fat
?
0g
0g
1g
0g
1 g*
* If a food has < 0.5 g of a
specific fat it can be labeled
as having “0 g.”
Insert Figure 6.14
Cardiovascular Disease (CVD)
• Diseases of the heart and blood vessels
– Heart disease (“coronary artery disease”)
– Stroke
• 1 in 3 adult Americans have some form of
CVD.
• In 2004, CVD was responsible for ~36% of
deaths in the U.S.
From Atherosclerosis to
Cardiovascular Disease
Atherosclerosis — disease in
which lipid-containing plaques
build up inside artery walls.
Insert figure 6.15
Plaque forms in arteries when
something irritates artery walls.
• Plaque narrows arteries,
interfering with circulation.
• Plaque may also result in the
formation of a fixed clot— a
thrombus.
Embolus Formation
A thrombus that breaks
away and travels through
the blood is an embolus.
• If an embolus lodges in
the heart, it can cause a
heart attack (myocardial infarction).
• If an embolus lodges in the brain and deprives brain cells of
oxygen and nutrients, a stroke can result.
Arteriosclerosis and Hypertension
Arteriosclerosis
- Condition that results from atherosclerosis
- Characterized by loss of arterial flexibility
- Commonly referred to as “hardening of the
arteries”
- Contributes to hypertension
Hypertension
- Chronic condition characterized by abnormally high
blood pressure levels
- May cause hardened arteries to tear or burst
Cardiovascular Disease: Major Risk Factors
Insert Table 6.3
Modifiable Risk Factors
Hypertension*
Diabetes*
Excess body fat*
Elevated blood cholesterol (LDL)*
Physical inactivity
*Influenced by diet
High-density Lipoproteins
HDL commonly
called “good”
cholesterol
• Transports
cholesterol away
from tissues and
to the liver where
it can be
eliminated
Insert Figure 6.18
Low-density Lipoproteins
LDL commonly
called “bad”
cholesterol
• Conveys
cholesterol to
tissues
• May become
oxidized LDL and
contribute to
atherosclerotic
plaque
Insert Figure 6.18
Roles of HDL, LDL, and Oxidized LDL
Insert figure 6. 19
Very Low-density Lipoproteins
High levels may
contribute to
atherosclerosis
VLDL primarily
carries
triglycerides
Insert Figure 6.18
Assessing Your Risk of
Atherosclerosis
Lipid Profile
Blood test that determines total
cholesterol, HDL and LDL cholesterol, and
triglyceride levels
Desirable levels:
Total Cholesterol
LDL Cholesterol
HDL Cholesterol
Triglycerides
< 200 mg/dl
< 100 mg/dl
> 40 mg/dl
< 150 mg/dl
C-reactive Protein
• High-sensitivity C-reactive protein
(hs-CRP)
- Protein produced primarily by liver in
response to infection and
inflammation
- Marker for CVD and hypertension
(“Marker” = early physiological warning
sign that can be measured)
Dietary Recommendations to
Reduce Risk of CVD
 Limit:
- saturated fats to <7% of kcal
- trans fats to <1% of kcal
- polyunsaturated fats to ~10% of kcal
- total fat to 35% or less of total energy
intake
 Choose unsaturated fats to replace
saturated and trans fats.
 Include omega-3 rich fish twice a week.
Dietary Recommendations to
Reduce Risk of CVD (continued)
 Include fiber-rich foods, especially
sources of soluble fiber.
 For people who consume
alcohol, limit to 1-2 drinks/day.
Rich Food Sources of Omega-3 Fatty Acids
Insert Table 6.5
Ways to Lower Your Risk of CVD
Insert Table 6.6
Genetic Factors
Homocysteine
- Amino acid associated with risk of CVD
- Vitamin B-6 and folate are needed to
metabolize homocysteine.
- Some people have a genetic predisposition
for high homocysteine levels.
High-fat Diet and CVD
- Scientists have identified gene that increases
risk of CVD, particularly when people with
the gene consume high-fat diets.
Should You Avoid Eggs?
• Eating an egg/day does not increase coronary artery disease
or stroke risk.
 Is It Safe to Eat Butter?
Common
Questions
About
• “Stick” margarine
may be more harmful
to health,Fats
because it
contains cholesterol-raising trans fat. Liquid or soft margarines
may be less harmful.
 Will Weight Loss and Exercise Help?
• Achieving a healthy body weight often reduces CVD risk.
Excess abdominal fat is associated with elevated LDL levels.
Food Selection and Preparation
Strategies to reduce dietary fat include:
Reduce intake of fried foods.
Purchase lean cuts of meat and trim visible
fat.
Replace some fatty foods with reduced-fat or
fat-free alternatives.
Replace high-fat sandwich meats with nut
butters.
Choose low-fat snack foods.
Use less salad dressing on salads.
Fat Replacers
Synthetic fat replacers developed to
meet consumer requests for lower fat
foods
Oatrim
Simplesse
Olestra
What If Lifestyle Changes Don’t Work?
People who cannot lower blood cholesterol
levels after lifestyle modifications may
need prescription drugs such as:
Statins — class of medications that
interfere with liver’s metabolism of
cholesterol
“Zetia©” — inhibits intestinal absorption
of cholesterol
Chapter 6 Highlight
Drink to Your Health?
Ethanol (“Alcohol”)
• Simple 2-carbon
compound
• In beer, wine,
vodka, whiskey,
sake, koumiss, and
kefir
Insert Figure 6.A
Alcohol Production
Alcohol production requires:
- Microbes (typically yeast)
- Warm conditions
- A source of simple sugar
Typical sugar sources for common
beverages are grains, fruits, and
potatoes.
Koumis is made from mare’s milk.
Kefir is from camel’s milk.
Approximate Alcohol, CHO, & Kcal
Contents of Alcoholic Beverages
Insert Table 6.A
How the Body Processes Alcohol
• Alcohol requires no digestion.
– Rapidly absorbed in the mouth, esophagus,
stomach, and small intestine
• Detoxification begins in stomach where
alcohol dehydrogenase metabolizes ~20%
of alcohol consumed.
– Most alcohol is absorbed in small intestine
– Travels to the liver where it is metabolized
Main Pathway for Alcohol Metabolism
At relatively low doses, the enzymes alcohol
dehydrogenase and acetaldehyde dehydrogenase
convert alcohol to acetyl CoA.
Acetyl CoA can be used to form glucose or fatty acids.
Insert Figure 6.B
2nd Pathway for Alcohol Metabolism
(Also occurs in the liver)
At high doses, the liver’s ability to metabolize
alcohol using the dehydrogenase pathway
is overwhelmed.
Under these conditions, the microsomal
ethanol oxidizing system (MEOS) is used.
- MEOS wastes energy as the heat
produced dissipates into the
environment.
Factors That Influence Alcohol Metabolism
Sex
- Men have
•
•
•
more gastric alcohol dehydrogenase
larger livers that can metabolize more alcohol at a time
more body water
As a result, a man’s BAC rises more slowly than a woman’s.
Inset Figure
6.D
Factors That Influence
Alcohol Metabolism
Prior Drinking History
Regular drinkers develop tolerance
– level of alcohol-detoxifying liver enzymes increase
As tolerance increases, alcohol dependence
(alcoholism) is likely to occur
Classifying Drinkers
Insert table 6.B
Alcohol Abuse and Dependence
Data on U.S. alcohol abuse:
- Based on U.S.D.H.H.S. data, ~ 15 million
Americans, over age 12 yrs, abused or were
dependent on alcohol in 2003.
- Alcohol abuse negatively affects 13% of
Americans at some point in their lives.
Alcohol Abuse vs Dependence
Abuse
Drinker:
- has control over
alcohol intake
- does not have a
powerful craving
for alcohol
- does not experience
withdrawal
symptoms
Dependence
Drinker:
- has uncontrollable
need to drink
- is unable to limit
alcohol
consumption
- suffers withdrawal
symptoms
- develops tolerance
to alcohol
Signs of Alcohol Abuse
Insert Table 6.C
Alcohol and Health
Effects vary from person to person due to:
- Differences in overall health
- Drinking habits
- Genetic backgrounds
Alcohol affects every cell in the body and
excesses can damage every organ system.
Alcohol and the Body
• Insert figure 6.D
Alcohol and the Brain
Effects on the CNS appear within a few
minutes after consumption.
Acts as a depressant, slowing
transmission of messages between nerve
cells.
Effects on the brain vary and depend on
blood alcohol concentration (BAC) .
Typical Effects of Alcohol at
Various BAC Levels
Insert Table 6.D
Alcohol and the Liver
Excessive amounts of alcohol are converted to
fatty acids in the liver.
“Fatty liver”
• condition is reversible if the person avoids alcohol.
Continued alcohol consumption results in fat
buildup in liver
• destroys liver cells and results in scar tissue formation
Liver cirrhosis — irreversible hardening of
liver
Alcohol and the Cardiovascular
System and Cancer
Cardiovascular system
Excess consumption can damage heart
muscle and elevate blood pressure.
Cancer
Chronic drinkers are more likely to develop
cancers of oral cavity, esophagus,
stomach, liver, pancreas, and
colon/rectum.
Alcohol and Drug Interactions
• Prescription and over-the-counter
medications may amplify effects of
alcohol.
• Alcohol may interact with certain
drugs, causing serious side effects.
Effects of Alcohol on Nutritional
Status
• Moderate alcohol stimulates appetite
• Excessive alcohol:
– inhibits appetite
– displaces intake of nutrient-dense foods
– interferes with body’s utilization of
certain vitamins, minerals, and fat
Alcohol and Body Water
• Alcohol is not a “thirst quencher.”
• It is a diuretic that suppresses the
production of antidiuretic hormone
(ADH).
– As a result, kidneys excrete more urine,
which is mostly water, and certain
minerals and vitamins.
Fetal Alcohol Syndrome
• Alcohol is toxic to cells, including
embryonic cells.
• Infants born with fetal alcohol
syndrome have physical
deformities and experience
developmental delays.
Who Should Avoid Alcohol?
Insert Table 6.E
Health Benefits of Alcohol
• Light to moderate alcohol intakes
– Raise HDL cholesterol
– Reduce blood levels of fibrinogen
• Decrease platelet stickiness
• Controversy over the health benefits of
alcohol
– Benefits of drinking red wine and beer
rather than white wine and liquor
• Alcohol itself or the antioxidants and certain
vitamins in beer and red wines may provide
health benefits.
Alcohol and Physical
Performance
• American College of Sports
Medicine recommends:
– Athletes should learn about alcohol’s
effects on health.
– Avoid excessive alcohol during the
48 hrs before an event.
– After exercise, avoid alcohol until
body is rehydrated.
Where to Get Help for Alcohol
Abuse or Dependence
• National Drug and Alcohol Treatment Referral Routing
Service
1-800-662-HELP
• Alcoholics Anonymous www.alcoholics-anonymous.org
• National Clearinghouse for Alcohol and Drug Information
ncadi.samhsa.gov
• AlAnon/Alateen www.al-anon.alateen.org