Fats and Other Lipids

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

2 6.1 Understanding Lipids Lipids include: 1. Fatty acids 2. Triglycerides 3. Phospholipids 4. Cholesterol Oil and Water Don t Mix Because oil is less dense than water, it floats on top. Lipids are insoluble in water less dense than water Chapter 6: Fats and other Lipids 2

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.

3 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

4 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

5 Essential Fatty Acids Essential - you must have them in your diet but your body can t make them! Chapter 6: Fats and other Lipids 5

6 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

7 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

8 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 Oils Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9 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. % Saturated % Monounsaturated % Polyunsaturated 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 Chapter 6: Fats and other Lipids Approximate Percentages (Values for each fat/oil may not total 100% because of rounding) The McGraw-Hill Companies, Inc./Elite Images, photographer;

10 Composed of 3 fatty acids attached to a glycerol backbone 2. Triglycerides ~ 95% of lipids in the body and foods is in the form of triglycerides. Chapter 6: Fats and other Lipids 10

soy Phospholipids act as emulsifiers, because they have hydrophobic and hydrophilic regions.

11 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.

12 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

13 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

14 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

15 Chapter 6: Fats and other Lipids Absorption 15 Lipid Digestion and

16 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

17 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.

18 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 store triglycerides as fat droplets. Adipose cells can break down triglycerides into fatty acid and glycerol molecules before releasing them into blood stream.

19 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) Adipose Cells Chapter 6: Fats and other Lipids 19

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

21 Understanding Nutritional Labeling: Lipids Chapter 6: Fats and other Lipids 21

22 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 a specific fat it can be labeled as having 0 g. Chapter 6: Fats and other Lipids 22

23 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

24 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

25 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

If an embolus lodges in the heart, it can cause a heart attack (myocardial

26 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

27 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

28 Major Risk Factors for CVD Chapter 6: Fats and other Lipids 28

Genetics and CVD Genetics (family history) cannot be modified. Genes may: code for physical conditions that increase risk hypertension and diabetes.

29 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

30 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

31 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

HDL commonly called good cholesterol Transports cholesterol away from tissues and to the liver where it can be eliminated Lipoproteins LDL commonly called bad cholesterol Conveys

32 HDL commonly called good cholesterol Transports cholesterol away from tissues and to the liver where it can be eliminated Lipoproteins 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

33 Roles of HDL, LDL, and Oxidized LDL Chapter 6: Fats and other Lipids 33

34 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 mg/dl* Triglycerides < 150 mg/dl * for men, 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

35 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

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

37 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. Chapter 6: Fats and other Lipids 37

38 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. Chapter 6: Fats and other Lipids 38

39 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 Chapter 6: Fats and other Lipids 39

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

41 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. Chapter 6: Fats and other Lipids 41

42 Ways to Lower Your Risk of CVD Chapter 6: Fats and other Lipids 42

43 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. Chapter 6: Fats and other Lipids 43

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

45 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 Chapter 6: Fats and other Lipids 45

46 Chapter 6: Fats and other Lipids Mediterranean Diet Pyramid 46

47 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: Fats and other Lipids 47

History. Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added. Fat deficiency severely affected

History. Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added. Fat deficiency severely affected Chapter 5 LIPIDS History 1918 Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added Fat deficiency severely affected Bone growth Reproduction Called Vitamin