C hapter 6
Chapter 6: Fats and other Lipids 1

• Lipids include:
1. Fatty acids
2. Triglycerides
3. Phospholipids
4. Cholesterol
• Lipids are
• insoluble in water
• less dense than water
“Oil and Water Don’t Mix”
Because oil is less dense than water, it floats on top.
Chapter 6: Fats and other Lipids 2

• 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.
• 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
Chapter 6: Fats and other Lipids 3

• 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.
Chapter 6: Fats and other Lipids 4

“ Essential ”- you must have them in your diet but your body can’t make them!
Chapter 6: Fats and other Lipids 5

• Precursors of prostaglandins
– Hormone-like substances formed from
EPA, DHA, and arachidonic acid
• (green ovals from previous slide)
• Effects of prostaglandins:
–
Stimulate uterine contractions
– Regulate blood pressure
– Promote immune system response
Chapter 6: Fats and other Lipids 6

• What are trans fats?
– Unsaturated fats with at least 1 trans double bond rather than the more common cis double bond
– *Fatty acids!*
• Hydrogenation:
– Process that adds hydrogen atoms to liquid vegetable oils to make trans fats
• Partial hydrogenation:
– Not all double bonds are hydrogenated.
– Natural cis double bonds convert to the unhealthy trans form.
– Has a longer shelf-life
Chapter 6: Fats and other Lipids 7

• 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.
Chapter 6: Fats and other Lipids 8

Approximate Percentages of
Saturated and Unsaturated Fatty Acids in
Common Fats and Oils
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
% Monounsaturated % Polyunsaturated % Saturated
Safflower oil
Sunflower oil
Soybean oil
Corn oil
Cottonseed oil
Peanut oil
Canola oil
Margarine (80% fat, partially hardened corn and soybean oils)
Chicken fat
Lard (pork fat)
Olive oil
Palm oil
Beef fat
Butter
Cocoa butter
Coconut oil
0
6.5
7.5
10.8
13.6
16.3
10
14.2
17.7
19.
0
15.1
20
27.1
20.4
31.2
30
23.7
29.0
18.6
41.0
40
51.6
52.1
50
62.4
65.6
60
48.6
64.0
50.0
70
46.8
(Values for each fat/oil may not total 100% because of rounding)
© The McGraw-Hill Companies, Inc./Elite Images, photographer;
80
47.2
75.0
38.7
92.0
43.7
4.2
30.5
4.0
34.4
3.0
6.0
2
21.9
11.7
10.8
9.7
78.4
68.8
60.0
57.4
54.3
33.7
28.5
31.0
90 100
9

• Composed of 3 fatty acids attached to a glycerol “backbone”
• ~ 95% of lipids in the body and foods is in the form of triglycerides.
Chapter 6: Fats and other Lipids 10

• Chemically similar to a triglyceride, 1 fatty acid is replaced
• by a compound containing phosphorus and nitrogen groups
• Lecithin - main phospholipid in foods, such as egg yolks, liver, wheat germ, peanut butter, and soy
• 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
Chapter 6: Fats and other Lipids 11

• Cholesterol is a sterol, a compound that is more complex than most other lipids. It is essential to our diet & only found in animal foods.
• The body uses cholesterol to make various substances, including:
– Vitamin D
– Steroid hormones
• Estrogen
• Testosterone
– Bile
Chapter 6: Fats and other Lipids 12

• Lingual lipase in the mouth is activated in the acidic stomach and small amounts of digestion can occur in the stomach.
• In the duodenum, pancreatic lipase digests triglycerides, forming primarily:
– Monoglycerides
– Free fatty acids
Chapter 6: Fats and other Lipids 13

• Bile made in the liver and stored in the gallbladder
• Bile contains bile salts that aid in lipid digestion.
• Without bile, lipids clump together in large fat globules
Chapter 6: Fats and other Lipids 14

15

• Chylomicrons are transported from the
SI through the lacteals in the lymphatic system
• Lymph vessels eventually return this into general circulation via the subclavian vein
Chapter 6: Fats and other Lipids 16

Chapter 6: Fats and other Lipids 17

• Enterohepatic
Circulation
– After bile salts are used to aid lipid digestion, the salts are absorbed in the ileum and return to liver for the production of new bile.
• Soluble fibers and plant sterols/stanols interfere with bile and cholesterol absorption. Note: Some synthetic margarine spreads contain plant sterols or stanols.
Chapter 6: Fats and other Lipids 18

• Adipose cells store triglycerides as fat droplets.
• Adipose cells can break down triglycerides into fatty acid and glycerol molecules before releasing them into blood stream.
– Liver can convert glycerol to glucose —another energy source.
• Triglycerides provide 9 kcal/g (carbohydrate & protein provide 4 kcal/g)
Chapter 6: Fats and other Lipids 19

• Do Americans eat more or less fat than 100 years ago?
– 1987 to 1988  approx.
54 lbs/year/person
– 2007 to 2008  63 lbs/year/person
• Fat contributes ~34% of the average American’s daily caloric intake.
• Acceptable
Macronutrient
Distribution Range  20 to 35% of total calories
• U.S. Dietary Guidelines
2010
– < 10% of calories from saturated fats
– < 300 mg cholesterol daily
– trans fatty acid intake as low as possible
20
Chapter 6: Fats and other Lipids

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)
Chapter 6: Fats and other Lipids 21

Label states: Total Fat
2 g
Saturated Fat 0 g
Trans Fat 0 g
Poly. Fat 1 g
Mono . Fat 0 g
?
1 g*
* If a food has < 0.5 g of a specific fat it can be labeled as having “0 g.”
Chapter 6: Fats and other Lipids 22

• CVD: diseases of the heart and blood vessels
• Most common forms of CVD are:
• Heart disease (“coronary artery disease”)
• Stroke
• 1 in 3 adult Americans have some form of
CVD.
– Responsible for ~30% of deaths in the U.S. in
2009
Chapter 6: Fats and other Lipids 23

• Atherosclerosis — disease in which lipid-containing plaques build up inside arteries
• Plaque forms in an artery when something irritates the lining of the artery wall.
• Plaque narrows arteries, interfering with circulation.
• Plaque may also result in the formation of a fixed clot — a thrombus.
Chapter 6: Fats and other Lipids 24

• Note differences between the cross sections of the two arteries. The one artery is almost blocked completely from atherosclerosis
Chapter 6: Fats and other Lipids 25

• 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 results.
Chapter 6: Fats and other Lipids 26

• What is
Arteriosclerosis?
– Condition that results from atherosclerosis
– Characterized by loss of arterial flexibility
– Commonly referred to as
“hardening of the arteries”
– Contributes to hypertension
• What is
Hypertension?
– Chronic condition characterized by abnormally high blood pressure levels
– May cause these hardened arteries to tear or burst
Chapter 6: Fats and other Lipids 27

Chapter 6: Fats and other Lipids 28

• Genetics (family history) cannot be modified.
– Genes may:
• code for physical conditions that increase risk hypertension and diabetes.
• influence way circulatory and immune systems respond to diet.
• Someday genetic testing may be available to determine markers for
CVD.
Chapter 6: Fats and other Lipids 29

• Smoking
• Hypertension*
• Diabetes*
• Excess body fat*
• Elevated blood cholesterol (LDL)*
• Physical inactivity
* Influenced by diet
Chapter 6: Fats and other Lipids 30

• Lipoproteins:
– Transport lipids in the blood
– Play major role in atherosclerosis development
– Carry different types of lipids and can influence plaque formation differently
– 3 types of lipoproteins:
1.
High density lipoproteins
– HDL
2.
Low density lipoproteins
– LDL
3.
Very Low density lipoproteins
– VLDL
Chapter 6: Fats and other Lipids
31

HDL
• commonly called
“good” cholesterol
• Transports cholesterol away from tissues and to the liver where it can be eliminated
LDL
• commonly called
“bad” cholesterol
• Conveys cholesterol to tissue.
• May become oxidized LDL & contribute to atherosclerotic plaque
VLDL
• May contribute to atherosclerosis
• Primarily carries triglycerides
Chapter 6: Fats and other Lipids 32

Chapter 6: Fats and other Lipids 33

• Lipid (Lipoprotein) Profile
– Blood test that determines total cholesterol, HDL & LDL cholesterol, and triglyceride levels
• Desirable levels:
– Total Cholesterol < 200 mg/dl
– LDL Cholesterol < 100 mg/dl
– HDL Cholesterol 40-60 mg/dl*
– Triglycerides < 150 mg/dl
• * 40-60 for men, 50-60 for women
Chapter 6: Fats and other Lipids 34

• High-sensitivity Creactive protein
– (hs-CRP)
– Protein produced primarily by liver in response to inflammation
• This protein is a marker for CVD and hypertension
– Note: A “marker” is an early physiological warning sign that can be measured.
Chapter 6: Fats and other Lipids 35

• Coronary calcium consists of specks of calcium (tiny calcifications) in arteries of the heart.
• Associated with: smoking and elevated total cholesterol.
Chapter 6: Fats and other Lipids 36

• Impact of dietary fat & cholesterol on blood lipids:
– Saturated fats increase LDL and HDL
– Trans fats increase LDL but lower HDL
– Cholesterol increases LDL
– Monounsaturated fats lower LDL but not HDL
– Polyunsaturated fats lower LDL and lower
HDL in some people.
Chapter 6: Fats and other Lipids 37

 Limit:
Saturated fats to <10% of total kcal
- Trans fats limited to as little as possible
 Choose unsaturated fats to replace saturated and trans fats.
Chapter 6: Fats and other Lipids 38

Omega-3
• Sources: Fatty fish, canola oil, walnuts, and flaxseed
• Actions: Reduces inflammation, blood clotting, and blood pressure
• May reduce risk of heart disease
Chapter 6: Fats and other Lipids
Omega-6
• Sources: Animal fats and vegetable oils
• Actions: Increases inflammation and blood clotting
• May also reduce risk of heart disease
39

Rich Food Sources of Omega-3 Fatty Acids
Chapter 6: Fats and other Lipids 40

 Should You Avoid Eggs?
• Dietary sources of cholesterol, such as eggs, does not increase blood cholesterol levels as much as dietary sources of saturated fat.
 Is It Safe to Eat Butter?
• “ Stick” margarine may be more harmful to health, 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.
Chapter 6: Fats and other Lipids 41

Chapter 6: Fats and other Lipids 42

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.
Chapter 6: Fats and other Lipids 43

Synthetic fat replacers were developed to meet consumer requests for lower fat foods.
 Oatrim
 Simplesse
 Olean
Chapter 6: Fats and other Lipids 44

• Increase soluble fiber intake
• Reduce intake of refined carbohydrates
• Monitor alcohol intake
– A small amount can raise HDL but increase blood triglyceride levels and blood pressure
• Lose excess body fat
• Follow the Mediterranean Diet Pyramid
Chapter 6: Fats and other Lipids 45

46

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: Fats and other Lipids 47