Fats: Essential Energy-Supplying Nutrients

1. Fats: EssentialEnergy-Supplying Nutrients

2. What Are Lipids? • Lipids: diverse class of molecules that are insoluble in water. • Lipids (fats) do not dissolve in water

3. Three types of lipids are found in foods • Triglycerides (the fats and oils) • Phospholipids (lecithin) • Sterols (cholesterol)

4. Triglycerides (the fats and oils) • Triglycerides are composed of • One glycerol molecule • Glycerol: a 3-carbon alcohol that is the backbone of a triglyceride • Three fatty acid molecules • Fatty acids: long chains of carbon atoms surrounded by hydrogen atoms

5. Triglycerides Figure 5.1

6. Triglycerides contain three fatty acids. • Fatty acids can differ in: • Length of their carbon chain • Short- (<6), medium- (6–12), or long- (>13) chain • Level of saturation • Saturation refers to how many hydrogen atoms surround each carbon • Shape (straight, slightly bent or very bent)

7. Triglycerides • Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain. No double bonds. • Monounsaturated fatty acids lack hydrogen atoms in one region. One double bond. • Polyunsaturated fatty acids lack hydrogen atoms in multiple locations. Two or more double bonds. • Note: Each double bond causes the loss of two hydrogen atoms. The molecule can bend or flex at the point where the double bond is. So, typically, the more double bonds, the more bent the molecule.

8. Saturated Fatty Acids are Rigid (straight) Figure 5.3a–b

9. Monounsaturated fatty acids have one double bond (and typically (cis) have one bend.) Figure 5.3c–d

10. The shape of a triglyceride is determined by the saturation of the three fatty acids it contains. • Saturated fatty acids can pack more tightly (stable) together and are solid at room temperature. • For example, coconut oil, animal fats, and butter, and rich sources of saturated fatty acids

11. Unsaturates are more bent • Unsaturated fatty acids are more bent and do not stack together well; they will be liquid at room temperature. • Unsaturated fatty acids are the predominant type in plants from temperate climates; • Plants grown in equatorial places are more likely to produce saturates. Examples include: coconut and palm kernel oil

12. The arrangement of hydrogen atoms about the double bond (point of unsaturation) determines if there are bends. • The hydrogen atoms at the unsaturated part of the molecule can be arranged in different positions. • Cis: same side of the carbon chain (these bend); in nature most, but not all fatty acids are cis. • Trans: opposite sides of the chain (these remain straight)

13. The cis arrangement has both hydrogens on the same side of the molecule. Figure 5.5

14. There is a food processing technique called hydrogenation that companies use to make oils into solid fats (we call them shortening in the U.S.) • Hydrogenation: the addition of hydrogen atoms to unsaturated fatty acids. • Converts liquid fats (oils) into a semi-solid (spreadable) or solid form • Used to create margarine from plant oil • Partial hydrogenation may create trans fatty acids • On the food label, look for the term partially hydrogenated oil • You may also see fully hydrogenated oil, in which case there is no trans fatty acid. But, to be honest, this process is hard on the oil and harms the quality of the product.

15. Research on Lipids and Health • trans fats from processed foods are harmful to health; they lower “good” cholesterol and raise “bad” cholesterol levels; • Trans fats from natural foods, such as cow milk from animals that eat green (not grains) are health-promoting; • Saturated fats can be healthful in the diet. They should be from minimally processed, natural foods such as butter, coconut and palm. • In the U.S., as of January 2006 trans fat content is required on the food label.

16. Fatty Acids and Health • Essential fatty acids • There are two fatty acids cannot be synthesized in the body. They are essential and must be obtained in the diet. • They are: • Linoleic acid (an omega 6 shape) • Alpha linolenic acid (an omega 3 shape) • They are converted into important regulatory compounds in the body.

17. The Omega-6 Essential LA • Linoleic acid (omega-6 fatty acid) • Found in vegetable and nut oils – such as corn and soy oil • Can be converted by the body to arachidonic acid which is involved in blood clotting and blood pressure • You can eat arachadonic acid, already formed, from animal milk, muscle and organ meats. • Arachadonic Acid (AA) will form important regulator molecules. • These are more pro-inflammatory.

18. The Omega-3 Essential: ALA • Alpha-linoleic acid (ALA)(omega-3 fatty acid) • Found in vegetables oils such as: chia, perilla, flax, lingonberry and purslane. • ALA is converted to EPA and DHA in our bodies – These contribute to the formation of important regulators of inflammation, blood clotting and blood pressure. These are more anti-inflammatory. • You can get EPA and DHA, already formed, in shellfish and fish.

19. Phospholipids • Phospholipids • Are composed of • Glycerol backbone • Two fatty acids • Phosphate plus another group • Have a very unusual character: one part of the molecule is soluble in water; another part is soluble in lipid • They are vital to build cell membranes

20. Phospholipids arrange themselves to put the fat-liking fatty acid legs (light brown) together and the phosphate head (blue color) at the outside. See how this builds a very effective membrane to surround each cell. Figure 5.7

21. Sterols • Sterols: lipids containing multiple rings of carbon atoms. • Are essential components of cell membranes and many hormones • Cholesterol is the major sterol found in the body • Our liver makes quite a bit of cholesterol each day, to serve many purposes.

22. Sterols: The basic sterol ring structure is shown at left; the cholesterol molecule is on the right. Figure 5.8

23. The Role of Fat • Energy • Fat is very energy dense, containing 9 kcal/gram or • Much of the energy used during rest comes from fat • Fat is used for energy during exercise, especially after glycogen is depleted • Fat is also used for energy storage

24. The Role of Fat • Fat-soluble vitamins • Vitamins A, D, E, and K are soluble in fat; fat is required for their transport • Fat is essential to many body functions • Cell membrane structure • Nerve cell transmissions • Protection of internal organs • Insulation to retain body heat

25. The Role of Fats • Fat provides flavor and texture to foods. • Fat contributes to making us feel satiated because • Fats are more energy dense than carbohydrates or protein • Fats take longer to digest

26. Digestion of Fats • Fats are not digested and absorbed easily because they are insoluble in water. • No digestion of fats occurs in the watery environments of the mouth • Minimal digestion occurs in the stomach from gastric lipase • Digestion and absorption of fats occurs primarily in the small intestine.

27. Digestion of Fats Figure 5.10

28. Digestion of Fats • As fat enters the small intestine • Bile is secreted from the gall bladder into the small intestine • Bile is produced by the liver and stored in the gall bladder • Bile disperses fat into smaller fat droplets • Pancreatic enzymes break triglycerides into two separate fatty acids and a monoglyceride • Fat enters the mucosal cell as a micelle (fatty acids, monoglycerides, phospholipids, and sterols)

29. Digestion of Fats • In the intestinal mucosal cell • Fatty acids are reattached to the monoglyceride to reform triglycerides • A small amount of protein is added to the lipids forming a chylomicron • Chylomicron: a lipoprotein produced by cells lining the small intestine • Composed of triglycerides surrounded by phospholipids and proteins • Soluble in water

30. Structure of a Lipoprotein – a sphere of fatty compounds (cholesterol and fatty acids) surrounded by a single layer of phospholipids and a few proteins(shown in purple). Figure 5.11

31. Digestion of Fats • Chylomicrons are the transport vehicle that removes absorbed fats from the small intestine. • Travel through the lymphatic system • Are transferred to the bloodstream • Just a note for you: short- and medium-chain fatty acids are absorbed more quickly since they are not arranged into chylomicrons.

32. Digestion of Fats • Once the chylomicron gets to a cell in the body, the triglycerides in the chylomicrons must be disassembled by lipoprotein lipase into two fatty acids and a monoglyceride before they can pass through the cell membrane • After entering the cell, the two fatty acids and monoglyceride reform a triglyceride • The triglyceride can be • Used immediately for energy • Used to make lipid-containing compounds • Stored in liver and muscle cells

33. Lipoproteins Vary in Composition and Function. Figure 5.17 (1 of 2)

34. Healthy people carry more of their lipids as HDL than as LDL. Figure 5.17 (2 of 2)

35. How Much Fat in Our Diet? • The Acceptable Macronutrient Distribution Range (AMDR) for fat: • 20–35% of calories should be from fat

36. How Much Fat? • The type of fat consumed is important. • Saturated fat should be no more than 7% of total calories • Trans fatty acids should be reduced to the absolute minimum • Most fat in our diets should be from monounsaturated fats (e.g., olive oil). • The book wants you to have a lot of polyunsaturated oils, but that puts you at risk for quite a few health challenges. Please ask in class when I’m on site.

37. Beneficial Fats • Increased consumption of “good” fats is advised • Increase consumption of omega-3 fatty acids • Flaxseed oil, fish, walnuts • Avoid consumption of contaminated fish • Mercury, PCB’s levels can be high some fish– especially top of the food chain predators (tuna, shark) • Eat small fish like anchovies, sardines, herring and such. They have good fats and no bad chemicals. 

38. Health Problems from Fat • Cardiovascular disease • Dysfunction of the heart or blood vessels • Can result in heart attack or stroke • The type of fat in our diet can contribute to or help protect against cardiovascular disease.

39. Cardiovascular Disease • Risk factors for cardiovascular disease include • Being overweight • Physical inactivity • Smoking • High blood pressure • Diabetes • High blood cholesterol

40. Transport Lipids: Like a shuttle bus… • There are four types of lipid transport molecules in the blood. They are: • Chylomicrons (dietary lipids) • VLDLs—very low-density lipoproteins • LDLs—low-density lipoproteins • “bad cholesterol” • HDLs—high-density lipoproteins • “good cholesterol”

41. Cardiovascular Disease • The text states that diets high in saturated fats • Decrease the removal of LDLs from the blood • Contribute to the formation of plaques that can block arteries • Increase triglyceride levels (chylomicrons and VLDLs) • BUT, I need you to know that plaques formed with saturates are very stable and do not break off and cause disruptions of blood flow (as those with polyunsaturates will). I think you need to eat some saturates in your diet. They are stable against oxidation and stable in plaque. (sara)

42. Cardiovascular Disease • Cross-section of (a) normal artery and (b) a partially blocked artery. It’s important to note that the blockage (plaque) is inside the wall of the artery and it crowds the area where blood needs to flow. Figure 5.16

43. Cardiovascular Disease • Trans fatty acids • Can raise blood cholesterol levels more than saturated fat • Are abundant in hydrogenated vegetable oils (margarine, vegetable oil spreads) • Should be reduced to the absolute minimum • Some communities in the U.S. have banned the use of trans fats in restaurant foods.

44. Cardiovascular Disease • How can certain fats protect against heart disease? • Diets high in omega-3 fatty acids (along with moderate exercise) can increase HDL “good” cholesterol levels.