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Fats and Other Lipids Chapter 6
1Chapter 6: Fats and other Lipids
6.1 Understanding Lipids
• Lipids include:1. Fatty acids
2. Triglycerides
3. Phospholipids
4. Cholesterol
• Lipids are• insoluble in water• less dense than water
2Chapter 6: Fats and other Lipids
“Oil and Water Don’t Mix”Because oil is less dense than
water, it floats on top.
1. 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.
• 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
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.
Chapter 6: Fats and other Lipids 4
Essential Fatty Acids“Essential”- you must have them in your diet but your body can’t make them!
5Chapter 6: Fats and other Lipids
Essential Fatty Acids
• 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
Trans Fats• 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
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.
Chapter 6: Fats and other Lipids 8
Approximate Percentages of Saturated and Unsaturated Fatty Acids in
Common Fats and OilsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or
display.
0
78.4
0
2
% Saturated % Monounsaturated % Polyunsaturated
Safflower oil
Sunflower oil
Soybean oil
Corn oil
Cottonseed oil
Peanut oil
Canola oil
Margarine (80% fat, partially hardenedcorn and soybean oils)
Chicken fat
Lard (pork fat)
Olive oil
Palm oil
Beef fat
Butter
Cocoa butter
Coconut oil
Approximate Percentages(Values for each fat/oil may not total 100% because of rounding)
6.5
10.8
16.3
15.1
20.4
23.7
29.0
18.6
48.6
64.0
50.0
46.8
47.2
75.0
38.7
100908070605040302010
6.092.0
3.0
4.0
4.2
9.7
10.8
11.7
21.9
31.0
28.5
33.7
54.3
57.4
60.0
68.8
34.462.4
65.6
52.1
51.6
41.0
27.1
31.2
13.6
17.7
7.5
19.
14.2
43.7
30.5
© The McGraw-Hill Companies, Inc./Elite Images, photographer;
9Chapter 6: Fats and other Lipids
2. 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.
10Chapter 6: Fats and other Lipids
3. Phospholipids• 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
4. Cholesterol
• 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
6.2 What happens to lipids in your body?
• 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
Gallbladder
• 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
Lipid Digestion and
Absorption
15
Chapter 6: F
ats and other Lipids
Journey Into the General Circulation• 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
Summary of lipid digestion and absorption
Chapter 6: Fats and other Lipids 17
Recycling Bile Salts• 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• 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
Lipid Consumption Patterns• 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 possibleChapter 6: Fats and other Lipids
20
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
Why “Grams of Fat” May Not Add Up
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 aspecific fat it can be labeledas having “0 g.”
22Chapter 6: Fats and other Lipids
Lipids and Health:Cardiovascular Disease (CVD)
• 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
From Atherosclerosis to Cardiovascular Disease
• 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
Healthy artery vs. Atherosclerotic artery• 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
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 results.
Chapter 6: Fats and other Lipids 26
Arteriosclerosis • 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
Major Risk Factors for CVD
28Chapter 6: Fats and other Lipids
Genetics and CVD• 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
Modifiable Risk Factors
• Smoking• Hypertension*• Diabetes*• Excess body fat*• Elevated blood cholesterol (LDL)*• Physical inactivity
*Influenced by diet
Chapter 6: Fats and other Lipids 30
Lipoproteins and Atherosclerosis• 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
LipoproteinsHDL
• 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
Chapter 6: Fats and other Lipids 32
VLDL• May contribute to
atherosclerosis• Primarily carries
triglycerides
Roles of HDL, LDL, and Oxidized LDL
33Chapter 6: Fats and other Lipids
Assessing Your Risk of Atherosclerosis
• 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
C-reactive Protein• High-sensitivity C-
reactive 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
• 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
Reducing Your Risk of Atherosclerosis: Dietary Changes
• 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.
37Chapter 6: Fats and other Lipids
Dietary Recommendations
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.
38Chapter 6: Fats and other Lipids
Omega-3 and Omega-6 Fatty Acids
Omega-3• Sources: Fatty fish,
canola oil, walnuts, and flaxseed
• Actions: Reduces inflammation, blood clotting, and blood pressure
• May reduce risk of heart disease
Omega-6 • Sources: Animal fats
and vegetable oils
• Actions: Increases inflammation and blood clotting
• May also reduce risk of heart disease
39Chapter 6: Fats and other Lipids
Rich Food Sources of Omega-3 Fatty Acids
40Chapter 6: Fats and other Lipids
Common Questions About Fats
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.
41Chapter 6: Fats and other Lipids
Ways to Lower Your Risk of CVD
42Chapter 6: Fats and other Lipids
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.
43Chapter 6: Fats and other Lipids
Fat Replacers
Synthetic fat replacers were developed to meet consumer requests for lower fat foods.
OatrimSimplesseOlean
44Chapter 6: Fats and other Lipids
Other Dietary Modifications
• 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
45Chapter 6: Fats and other Lipids
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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
47Chapter 6: Fats and other Lipids