Fats and Other Lipids C hapter 6 1Chapter 6: Fats and other Lipids

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


“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.


Essential Fatty Acids“Essential”- you must have them in your diet but your body can’t make them!


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


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


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.


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;


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.


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


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


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


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


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


Summary of lipid digestion and absorption


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.


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)


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))


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.”


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


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


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.


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


Major Risk Factors for CVD


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.


Modifiable Risk Factors

• Smoking• Hypertension*• Diabetes*• Excess body fat*• Elevated blood cholesterol (LDL)*• Physical inactivity

*Influenced by diet


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


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


VLDL• May contribute to

atherosclerosis• Primarily carries

triglycerides

Roles of HDL, LDL, and Oxidized LDL


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


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.


Coronary Calcium

• Coronary calcium consists of specks of calcium (tiny calcifications) in arteries of the heart.

• Associated with: smoking and elevated total cholesterol.


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.


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.


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


Rich Food Sources of Omega-3 Fatty Acids


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.


Ways to Lower Your Risk of CVD


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 were developed to meet consumer requests for lower fat foods.

OatrimSimplesseOlean


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


Med

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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


Documents

Fats and Other Lipids C hapter 6 1Chapter 6: Fats and other Lipids