1. 1 Chapter 3: Fats

2. Introduction 2  Fats are a storage form of concentrated fuel for the human energy system  They supplement CHO, the primary fuel, as an available energy source  In food  solid fat or liquid oil  Not soluble in water  Greasy

3. Objectives 3 Identify the : nature of fats functions of fats food sources of fat body needs of fat digestion of fat dietary fat requirements

4. Fats 4 Fat: - an essential nutrient - concentrated storage fuel - tissue need - health hazard when consumed in excess

5. Fats Key concepts  Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material  Food from animal and plant sources supply distinct forms of fat that affect health in different ways  Excess dietary fat, esp. from animal food sources, is a health risk factor 5

6. Classes of fats 6 “Lipid” is another word for fat. “Lipos” is the Greek word for fat E.g. Hyperlipidemia; liposuction Include fats, oils, waxes, and other fat-related compounds such as cholesterol Glycerides: made up of glycerol with fatty acid(s) attached The principal constituents of adipose (fat) tissue Found in animal and vegetable fats and oils

7. Classes of fats 7 Triglycerides- made up of carbon, hydrogen and oxygen Most have three (“tri”) fatty acids attached to their glycerol base so they are called triglyceride. FATTY ACID + GLYCEROL = GLYCERIDE 3 Fatty Acids + glycerol base = TRIglyceride Other: 1 fatty acid + glycerol base = monoglyceride 2 fatty acids + glycerol base = diglyceride

8. Fatty Acids 8 Main building blocks of fat Fatty acids have 2 significant characteristics: 1. Saturated or unsaturated Fatty acids are “saturated” or “unsaturated” according to whether or not they are filled with hydrogen 2. Essential or nonessential

9. Fatty Acids 9 Saturated fatty acid = “saturated fat: Eg. Sponge – “saturated” with water when it holds all the water that it can hold A saturated fatty acid is one whose structure is filled with all of the hydrogen bonds that it can hold, and as a result, is heavier, more dense, and more solid (eg. meat fat)

10. Fatty Acids 10 Unsaturated fatty acid – Not filled with all the hydrogen that it can hold  less dense, less heavy If the component fatty acid has 1 unfilled spot = monounsaturated Olives, olive oil, peanut oil, avocados If the component fatty acid has 2+ unfilled spots = polyunsaturated Vegetable oils: safflower, corn, cottonseed, and soybean

11. Fatty Acids Most fatty acids in plants are unsaturated (except coconut and palm oils which are saturated) 11

12. Fatty acids 12 Trans fats:  Hydrogenated (hardened) products made from the “cis” and “Trans” forms of unsaturated fatty acids  Cis and Trans refer to two different shapes that a fat molecule can have as its structure

13. Fatty acids  When vegetable oils are “partially hydrogenated” to make food products, the normal bend is changed so that the chains of atoms are on opposite sides of the central bond.  This form is called “trans” or “opposite side” 13

14. Fatty acids 14 Trans Fats- Unsaturated fatty acids become rancid relatively quickly. To combat the instability of unsaturated fatty acids, manufacturers “hydrogenate” them, a process that makes them more stable  more solid and longer lasting form of vegetable oil called “partially hydrogenated” oil. This process increases shelf life, but has bad effects on the human system

15. Fatty acids 15 Trans Fats - When unsaturated vegetable fats are subjected to the process of hydrogenation, a new type of fatty acid is formed  “trans fatty acid” Trans fatty acids increase total cholesterol levels: increase LDL cholesterol (“bad”) Decrease HDL cholesterol (“good”)

16. Fatty acids 16 Trans Fats - Foods containing relatively large amounts of trans fatty acids: Stick margarine Tub margarine High-fat baked goods (doughnuts, cookies, cakes) French-fries, potato chips Any product for which the labels states: “partially hydrogenated vegetable oils”

17. Fatty acids 17 (Trans fats cont.) Heart-healthy fatty acids: Vegetable oils: canola, peanut, olive oil, flax, corn, safflower and sunflower - as long as they have not been subjected to hydrogenation Contain mono- and poly- unsaturated fatty acids which can reduce total cholesterol and increase HDL.

18. Fatty acids 18 (Trans Fats cont.)  3 steps to reducing the amount of “bad” fat and substituting “good” fat:  AVOID saturated fatty acids found in meat and dairy products as well as the topical oils  AVOID commercially fried foods, high-fat baked goods, and stick margarines  Whenever possible, substitute one of the natural unsaturated vegetable oils in recipes calling for stick margarine, butter, or lard

19. Essential Fatty Acids 19 Terms “essential” and “non essential” refer to the nutrient necessity in a diet. A nutrient is essential if:  absence of it will cause a specific deficiency disease  the body cannot manufacture it in sufficient amounts and it must be obtained from the diet 2 essential fatty acids for the human body:  Linoleic Acid  Linolenic Acid

20. Essential Fatty Acids 20 Linoleic Acid – 17 gm per day Male and 12 gm per day Female Linolenic Acid – 1.6 gm per day Male and 1.1 gm for Women. Found in milk, soybean, flaxseed oil

21. Essential Fatty Acids Both of these fatty acids help with tissue strength, cholesterol metabolism, muscle tone and blood clotting and heart action. EFA  The only fatty acids known to be essential for complete human nutrition are the polyunsaturated fatty acids 21

22. Lipoproteins 22 Combinations of fats, protein and other fat related substances The major vehicle for transport in the blood stream Fat is insoluble in water and blood is mainly water, it needs a water-soluble carrier to get around. (Fat cannot travel freely in the blood stream.) The body solves this problem by wrapping small particles of fat in a covering of protein (“lipoprotein”) which is soluble in water.

23. Lipoproteins 23 The blood then carries these little packages of fat to and from the cells to supply needed nutrients. A lipoprotein’s relative load of fat and protein determines its density: - The higher the protein load, the higher the lipoprotein’s density. (HDL) - The higher the fat load, the lower the lipoprotein’s density (LDL)

24. Lipoproteins 24 LDL= Groups of low-density lipoproteins carry fat and cholesterol to cells HDL= Groups of high-density lipoproteins carry free cholesterol from body tissue to the liver for breakdown and excretion All lipoproteins are closely associated with lipid disorders and the underlying blood vessel disease in heart attacks.

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26. Cholesterol 26 Cholesterol should not be confused with saturated fat Cholesterol belongs to a group of chemical substances called “sterols”: A vital substance in human metabolism that occurs naturally in all animal foods No cholesterol in plants Cholesterol is synthesized by the body in the liver

27. Cholesterol 27 Main food sources of cholesterol: Egg yolks, organ meats- like liver or kidney - as well as other meats No biological requirement for dietary cholesterol and no DRI set for cholesterol consumption. However, Epidemiology studies have found that there is a link between cholesterol intake and coronary heart disease

28. Functions of Fat 28 Fat in foods: Energy – Fats serve as fuel for energy and are an important storage form of body fuel. Essential nutrients Supply the body with essential fatty acids Carry fat-soluble vitamins and aid in their absorption Fat-soluble vitamins: A, D, E, K

29. Functions of Fat 29 Flavor and satisfaction – contributes to the feeling of satiety d/t slower rate of digestion than CHO Fat substitutes- are compounds that are not absorbed and contribute little or no kcals. These also provide flavor and physical texture to low fat foods.  Reshape protein  Develop indigestible form of sucrose  Simplesse, Olestra Long-term safety is not well established due to relative newness of these substitutes

30. Fat in the body 30 Adipose tissue – Tissue in the body which gives us padding, tissue support, vital organs protection, insulation (regulates body temperature), protection of nerves and helps relay nerve impulses Cell membrane structure – Fat forms the fatty center of cell walls and helps carry nutrient material across cell membrane

31. Food Sources of Fat 31 Animal fats – Most concentrated; increase cholesterol:  Meat foods such as bacon, sausage  Dairy fats and products  Egg yolks  Lean portions of meat can decrease cholesterol

32. Plant fats – supply most monounsaturated and polyunsaturated fats  safflower oil  corn  Cottonseed  Soybean  Peanuts  Olives Note that coconut and palm oils are plant-based, but do contain saturated fats 32

33. Food Sources of Fat 33 Hydrogenated fats- Modified vegetable oils by adding hydrogen  trans fatty acid food products Can add vitamins or cultured products to the oil to attempt to equal the nutritional value of the food for which it is substituted E.g. Margarine for butter

34. Food Label Information 34 Content of Information: Mandatory and Voluntary Mandatory: Calories from fat Total fat Saturated fat Cholesterol Voluntary: calories from saturated fat, trans fat, polyunsaturated fat, monounsaturated fat

35. Food Label Information 35

36. Characteristics of Food Fat Sources 36 Visible fat – butter, margarine, cream, salad dressing, bacon, sausage and salt pork. Easier to control in the diet Invisible (hidden) fat – cheese, milk, egg yolk, nuts, seeds, olives, avocados, lean meat

37. Characteristics of Food Fat Sources 37 Digestibility and market availability of food fats: Vary:  food source: butter digests more easily than meat fat  cooking method: fried foods, especially those saturated with fat in the frying process, are digested more slowly than baked or broiled foods When fried foods are cooked at too high of a temperature, they are more difficult to digest because substances in the fat break down into irritating materials.

38. Definitions 38 Bile – secreted by the liver and transported to the gallbladder for concentration and storage Released into the duodenum with the entry of fat Facilitates enzymatic fat digestion by acting as an emulsifier Emulsifier– An agent that breaks down large fat globules into smaller particles

39. Definitions Micelles– Packages of free fatty acids, monoglycerides and bile salts Chylomicron– Lipoprotein formed in the intestinal cell composed of triglycerides, cholesterol and phospholipids and protein. Allows for the absorption of fat into the lymphatic circulatory system before entering the blood circulation 39

40. Digestion of fats 40 In “digestion” plant and animal fats (basic fuel fats) are changed into refined fuel that cells can burn for energy. Mouth – Initial chemical breakdown begins in the mouth + mechanical action (chewing) + moisture. Lingual lipase: secreted by Ebner’s glands in the back of the tongue Important only in infancy

41. Digestion of Fats 41 Stomach – Fat is mixed with stomach contents by muscle action.  Gastric lipase acts on emulsified butter fat.  Note: No significant amount of fat enzymes are present in gastric secretion Specific digestive agents come from the gallbladder, pancreas and small intestine

42. Digestion of Fats Gallbladder:  The fat coming into the duodenum, the first section of the small intestine, stimulated the secretion of cholecystokinin, a hormone released from glands in the intestinal walls.  Cholecystokinin causes the gall bladder to contract, relax its opening muscle, and secrete bile into the intestine 42

43. Digestion of Fats Bile is an emulsified that prepares fat for chemical digestion by: Breaking the fat into smaller pieces allowing more surface area for enzyme action Decreasing surface tension of fat particles, allowing enzymes to penetrate more easily 43

44. Digestion of Fats 44 Pancreatic Lipase: Pancreatic juice flowing into the small intestine contains an enzyme for triglycerides and another for cholesterol Pancreatic Lipase: a powerful fat enzyme Small intestine- Fat digestion occurs primarily in small intestines: Major enzymes needed for chemical changes are present here

45. Digestion of Fats 45 In the small intestine the triglycerides are turned into diglycerides and monoglycerides and then to fatty acids and glycerol Absorption – fatty acids, monoglycerides and glycerol are absorbed. Some remaining fat may pass into large intestines for fecal elimination

46. 46 1.Very minor fat digestion in stomach 2.Fat digested mainly into monoglycerides and fatty acids by lipase enzyme released from the pancreas 3.Bile made by the liver aids fat digestion and absorption 4.Fat absorbed is mostly made into chylomicrons after triglycerides are resynthesized in the small intestine and transferred into lymph 5.Less than 5 % of fat normally excreted in feces

47. Body Needs for Fats 47 Americans, age 2 and older eat an average of 134 % of the recommendations based on Dietary Reference Intakes No more than 20 – 35% of a person’s total kcal should come from fat

48. Body Needs for Fats Health problems-  Amount of fat- too many Kcal in diet- regardless of source- will exceed requirements  Type of fat – excess cholesterol and saturated fat in diet will increase risks for atherosclerosis, heart disease, and strokes 48

49. Body Needs for Fat Health promotion- review lifestyle risk factors for children/adults. See “Clinical Application” box “How much fat are you eating?” (p.41) Fast-food industry: gradually decreasing the fat content in their products 49

50. Dietary fat requirements 50 Review fat content of the diet Dietary Reference Intakes 20 % -35 % of total Kcal 10 % should be saturated *dietary cholesterol limited to 300mg /day Dietary Guidelines for Americans recommend general control of fat – esp. saturated fat and cholesterol.