1. Triglycerides Phospholipids Sterols
Chapter 5 The Lipids:
Triglycerides
Phospholipids
Sterols

2. Objectives for Chapter 5
Discuss synthesis, structures, classification, function and metabolism of lipids
Identify the dietary sources of the different types of lipids
Discuss the role of lipoprotein in transport of lipids
Describe the relationship of lipids to chronic diseases
List current dietary recommendations for lipids and how to implement them.

3. Lipids Lipids are a class of nutrients that includes:
Triglycerides (fats and oils)
Phospholipids
Sterols.
Composed of carbon, hydrogen, and oxygen.
Lipids are hydrophobic (insoluble in water)
Include fat soluble vitamins (ADEK)
Provides 9 kcal per gram

4. Triglycerides
TG (fats and oils) – composed of 3 fatty acids attached to a glycerol
Fatty acid - is a chain of carbon atoms with hydrogen attached that has an acid group (COOH) at one end and a methyl group (CH3) at the other end
Glycerol is an alcohol composed of a three carbon chain

5. Methyl end Acid end Fig. 5-1, p. 140 Figure 5.1: Acetic Acid.
Acetic acid is a two-carbon organic acid.
Fig. 5-1, p. 140

6. TG

7. Triglycerides
Fats are lipids that are solid at room temperature (70 degrees)
Oils are lipids that are liquid at room temperature (70 degrees)
TGs are 95% of dietary fats
Roles of TGs
Energy reserve when stored
Insulation
Shock protection
Use carbohydrate and protein efficiently

8. Fatty Acids
Fatty acids Fatty acids vary in carbon chain lengths, degree of unsaturation, and number of double bonds.
Length of the carbon chain
Long-chain fatty acids are found primarily in meat, fish, and vegetable oils.
Medium- and short-chain fatty acids are found in dairy products.
Degree of Saturation- Saturation affects the physical characteristics of the fat and its storage properties
Saturated fatty acids carry the maximum possible number of hydrogen atoms.

9. Saturated vs. Unsaturated
Saturated - When most of the fatty acids are saturated it is called a saturated fat.
Stearic acid, an 18-carbon saturated fatty acid

10. Saturated vs. Unsaturated
Unsaturated – Unsaturated fatty acids are missing at least 2 hydrogen atoms and have at least one double bond. There are 2 types
Monounsaturated fatty acid (MUFA)
Oleic acid, an 18-carbon monounsaturated fatty acid

11. Saturated vs. Unsaturated
Polyunsaturated fatty acids (PUFA)
lack four or more hydrogen atoms and have at least two or more double bonds.
Linoleic and linolenic acid - Essential Fatty Acids (EFAs)
When most of the fatty acids in a lipid are polyunsaturated it is called a polyunsaturated fat.
Linoleic acid, an 18-carbon polyunsaturated fatty acid

12. Saturated vs. Unsaturated
Locations of the double bonds
Omega3 - linolenic acid - the first double bond is located at the third carbon from the methyl side
Omega 6 - linoleic acid - the first double bond is located at the sixth carbon from the methyl side
Linoleic acid, an 18-carbon polyunsaturated fatty acid

13. Omega-3 and Omega-6 Fatty Acids Compared

14. Saturated and Unsaturated Fatty Acids Help Shape Foods

15. Fatty Acids Firmness Stability Degree of unsaturation
Saturated fats - solid at room temperature. Mostly from animal sources
Polyunsaturated fats - liquid at room temperature. Found in vegetable oil except, cocoa butter, palm oil, palm kernel oil, and coconut oil
Stability
Saturated fat is more resistant to oxidation.
Monounsaturated fat is less susceptible to spoilage.
Polyunsaturated fat spoils most readily.

17. Essential Fatty Acids Essential Fatty Acids
Linoleic Acid - Omega-6 Family and 18 carbon
They are PUFA,
Can make arachidonic acid—a conditionally essential fatty acid with 20 carbons and 4 double bonds
Supplied by vegetable oils and meats

19. Essential Fatty Acids Linolenic Acid and 18 Omega-3 Family
EPA - eicosapentaenoic acid, 20 carbon, 5 double bonds
DHA - docosahexaenoic acid, 22 carbons and 6 double bonds
important for eyes, brain development, and heart disease.
Eicosanoids – omega 3 & 6
Made from arachidonic acid and EPA
Like hormones but have different effects on different cells
Include prostaglandins, thromboxanes, and leukotrienes
Essential fatty acid deficiencies are rare in the US but my occur in children fed low fat or fat free diet

20. Essential Fatty Acids

21. Fatty Acids Hydrogenation – Trans-Fatty Acids vs. Cis
Hydrogen atoms are added to monounsaturated or polyunsaturated fats
Act more like saturated fats
resistant to oxidation
Prolong shelf life
Becomes solid at room temperature
Trans-Fatty Acids vs. Cis
Naturally, most double bonds are cis, hydrogen next to the double bonds are on the same side.
Trans, hydrogens on opposite side of the carbon.
Trans fatty acids behave like saturated fat in the body.

22. Cis- and Trans-Fatty Acids Compared

23. Major Food Sources of Trans Fat for American Adults

24. Phospholipids Phospholipids
contain glycerol, 2 FAs and a phosphate group with a choline.
A well-known phospholipid is lecithin, made by the liver
Food sources of lecithin include eggs, liver, soybeans, wheat germ and peanuts.
Soluble in both water and fat
Roles of phospholipids
Transport lipids and FSV through Plasma membrane
Used as emulsifiers in food industry

25. Phospholipids

26. Sterols Sterols cholesterol, vit D, testorone Multiple-ring structure.
Found in plant and animal foods
Cholesterol is found in animal foods only - meat, eggs, fish, poultry and dairy products

27. Sterols

28. Sterols Roles of sterols
Needed to make bile acids, sex hormones, adrenal hormones and vitamin D
Component of cell membranes
Liver produces mg of cholesterol daily
Cholesterol forms deposits in the artery wall causing artherosclerosis.

29. Fat Digestion Mouth – Stomach—
hard fat begin to melt as they reach body temperature
salivary glands - lingual lipase digests short and medium chain fatty acids found in milk.
Stomach—
Lingual lipase breaks down triglycerides to produce diglycerides and fatty acids
gastric lipase breaks down a small amount of fat.
Little fat digestion takes place in the stomach.

30. Fat Digestion Small Intestine – Colon or large intestine
most of the digestion takes place in the small intestine.
Cholecystokinin (CCK) signals gallbladder to release bile.
Pancreatic and intestinal enzymes breaks lipids to monoglycerides and fatty acids.
Phospholipids are broken down as well.
Sterols are absorbed intact as is.
Bile is reabsorbed in the small intestine
Colon or large intestine
Soluble fibers traps some bile and excreting it from the body through the large intestine.

31. Lipid Absorption Lipid Absorption
Glycerol and short and medium-chain fatty acids diffuse and are absorbed directly into the bloodstream.
Monoglycerides and long-chain fatty acids form micelles, are absorbed, and are reformed into new triglycerides.
With protein they are transported by chylomicrons

32. Long-chain fatty acids
Monoglyceride
Micelle
Protein
Triglyceride
Long-chain fatty acids
Chylomicron
Figure 5.17: Animated! Absorption of Fat.
The end products of fat digestion are mostly monoglycerides, some fatty acids, and very little glycerol. Their absorption differs depending on their size. (In reality, molecules of fatty acid are too small to see without a powerful microscope, whereas villi are visible to the naked eye.)
Large lipids such as monoglycerides and long-chain fatty acids combine with bile, forming micelles that are sufficiently water soluble to penetrate the watery solution that bathes the absorptive cells. There the lipid contents of the micelles diffuse into the cells.

33. Lipid Transport
Lipid transport is made possible by a group of vehicles known as lipoproteins. There 4 lipoproteins
Chylomicrons
Largest of the lipoproteins
Least dense
Get smaller as triglyceride portion is removed by the cells
VLDL (Very-Low-Density Lipoproteins)
Composed primarily of triglycerides
Made by the liver
Transport lipids to the tissues
Get smaller and more dense as triglyceride portion is removed

34. Lipid Transport 3. LDL (Low-Density Lipoproteins)
Composed primarily of cholesterol
Transport lipids to the tissues
4. HDL (High-Density Lipoproteins)
Composed primarily of protein
Transport cholesterol from the cells to the liver

35. Chylomicrons: One Type of Lipoprotein

36. The Various Types of Lipoproteins and Their Composition

37. Lipid Transport Health Implications
High LDL is associated with higher risk of heart attack and is known as “bad” cholesterol.
High HDL seems to have a protective effect and is known as “good” cholesterol

38. Storing Fat Storing Fat as Fat Using Fat for Energy
Adipose tissue readily stores fat.
Provides twice the energy as carbohydrate and protein
1 lb of body fat = 3,500 cal
Lipoprotein lipase (LPL) breaks triglycerides as they pass, directs the parts into the cells to be used for energy or storage.
Using Fat for Energy
Fat supplies 60% of the body’s ongoing energy needs.
lipase inside the adipose cells hydrolyzes triglycerides when needed for energy.
Fasting metabolizes fat but needs carbohydrate and protein for complete breakdown.
Ketone bodies

39. Health Effects of Lipids
Normal blood lipid profile
Total cholesterol  200 mg/dL
LDL cholesterol  100 mg/dL
HDL cholesterol  60 mg/dL
Triglycerides  150 mg/dL
Atherosclerosis - Cholesterol accumulates in the arteries
saturated fats raise LDL
Trans fat increase LDL cholesterol and decrease HDL cholesterol
Cholesterol has less effect on blood cholesterol than saturated fat and trans fat.

40. Atherosclerosis

41. Health Effects of Lipids
Increasing dietary MUFA & PUFA is the most effective way to prevent heart disease.
omega-3 fats help to reduce risk of heart disease and stroke
Balance omega-6 and omega-3 intakes
Cancer - Fat does not initiate cancer development but may be a promoter once cancer has developed
Obesity- consequence of high fat diet

42. Recommended Intakes of Fat
DRI and the 2005 Dietary Guidelines recommends fat at % of energy intake.
FDA - 10% of energy intake from saturated, 30% of energy intake total fat
2005 Dietary Guidelines - choose a diet low in saturated fat and cholesterol and moderate in total fat.

43. Recommended Intakes of Fats
Daily Values
65 g fat based on 30% of 2000-kcal diet
20 g saturated fat based on 10% of 2000-kcal diet
300 mg cholesterol
USDA Food Guide considers saturated fats discretionary kcalories.
Too little fat can be detrimental to health.

44. Recommended Intakes of Fat
Linoleic acid AI
5% - 10% of energy intake
Linolenic acid AI
% of energy intake

45. Reducing Fat In Your Diet
Cook with olive oil
Nibble on nuts
Feast on fatty fish, high in omega 3
But beware of mercury
Limit Fatty Meats, Milk Products, and Tropical Oils
Limit hydrogenated foods

46. Reducing Fat in Your Diet
Fat replacers
Artificial, ingredients derived from carbohydrate, protein or fat.
Replace fat in foods, but no added kcalories
Olestra is safe but it deceases absorption of fat-soluble vitamins and may cause diarrhea.
Limit Fatty Meats, Milk Products, and Tropical Oils
Limit Hydrogenated Foods
Adopt the Mediterranean diet
Focus on whole grains, potatoes, and pasta, vegetables and legumes, low fat cheeses, yogurt, fruits, fish and seafood, poultry, a few eggs and little meat

47. Homework
Extra credit 5 points: Go to the supermarket and compile a list of 10 foods that contain hydrogenated fat in the ingredient list and document the amount of trans fat listed on the nutrition fact panel