1. Lipids: Essential Energy-Supplying Nutrients5
Lipids: Essential Energy-Supplying Nutrients 1

2. What Are Lipids? Lipids Fats
Diverse group of molecules that are insoluble in water
Fats
The lipid content of diets and foods 2

3. What Are Lipids?
Three types of lipids are found in foods and in body cells and tissues:
Triglycerides
Phospholipids
Sterols 3

4. Triglycerides Triglycerides (triacylglycerides) contain:
Three fatty acid molecules
One glycerol molecule 4

5. Triglycerides Fatty acids are classified by: Carbon chain length
Saturation level
Shape 5

6. Triglycerides: Chain Length
Short-, medium-, or long-chain fatty acids
Carbons can be numbered
Carboxyl end (COOH): -carbon (alpha—first)
Methyl end (CH3): Ω-carbon (omega—last)
Determines method of lipid digestion, absorption, metabolism, and use 6

8. Triglycerides: Saturation
Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain
Monounsaturated fatty acids lack one hydrogen atom (one double bond)
Polyunsaturated fatty acids have more than one double bond 8

10. Triglycerides: Shape Determined by the saturation of the carbon chains
Saturated fatty acids pack tightly together and are solid at room temperature
Animal fats, butter, and lard are high in saturated fatty acids 10

12. Triglycerides: Shape
Unsaturated fatty acids do not stack together well and are more liquid at room temperature
Hydrogen atoms at the unsaturated part can be arranged in different positions:
Cis: same side of the carbon chain
Trans: opposite sides of the chain 12

14. Triglycerides
Hydrogenation: hydrogen atoms are added to unsaturated fatty acids
Make oils more solid and more saturated
Create trans fatty acids
Reduce oxidation; resist rancidity
Increase risk of cardiovascular disease 14

15. Triglycerides
Essential fatty acids: cannot be made by the body and must be obtained from food
Linoleic acid (omega-6 fatty acid)
Found in vegetable and nut oils
Alpha-linolenic acid (omega-3 fatty acid)
Found in vegetables, soy, flaxseeds, walnuts 15

18. Triglycerides Omega-3 fatty acids found in fish and fish oil
Eicosapentaenoic acid (EPA)
Docosahexaenoic acid (DHA)
Reduce risk of heart disease
Stimulate prostaglandins and thromboxanes that reduce inflammatory responses
Reduce blood clotting and plasma triglycerides 18

19. Phospholipids Phospholipids contain Soluble in water
Glycerol backbone, two fatty acids, phosphate
Soluble in water
Transport fat in the bloodstream
Manufactured in our bodies (not required) 19

21. Sterols Sterols contain multiple rings of carbon atoms
Plant sterols appear to block the absorption of dietary cholesterol
Cholesterol is made in our bodies and therefore is not necessary in the diet
Sex hormones, vitamin D, bile 21

23. Digestion of Fats Fat digestion begins in the small intestine
Cholecystokinin (CCK) and secretin: gallbladder contractions release bile
Bile is produced by the liver and stored in the gallbladder
Bile emulsifies fat into small droplets
Pancreatic enzymes break fat into two fatty acids and a monoglyceride
Fat Digestion 23

25. Absorption of Fats Lipoprotein transports lipids for absorption
Chylomicron: lipoprotein produced in intestine to transport lipids from a meal
Composed of fatty acids surrounded by phospholipids and proteins
Soluble in water 25

26. Absorption of Fats
Chylomicrons are absorbed by cells of the small intestine, then:
Travel through the lymphatic system
Transferred to the bloodstream
Short- and medium-chain fatty acids are absorbed more quickly since they are not arranged into chylomicrons 26

27. Absorption of Fats
Triglycerides in the chylomicrons must be disassembled by lipoprotein lipase before they can enter body cells
In body cells, triglycerides can be:
Used immediately for energy
Used to make lipid-containing compounds
Stored in muscle and adipose tissues
Lipid Absorption 27

32. The Roles of Fat 9 kcal per gram Major fuel at rest Endurance exercise
Stored energy
Essential fatty acids
Fat-soluble vitamins
Regulates cell function
Maintains membrane
Protects the body
Provides flavors and textures of foods
Helps us feel satiated 32

34. How Much Fat?
Acceptable Macronutrient Distribution Range (AMDR) for fat: 20−35% of calories
Minimize saturated and trans fatty acid intake to lower risk of heart disease
Active people may need more energy from carbohydrates and can reduce their fat intake to 20−25% of total calories 34

35. How Much Fat?
Dietary Reference Intakes (DRIs) set for essential fatty acids
Linoleic acid: AMDR of 5−10% of energy
Alpha-linolenic acid: 0.6−1.2% of energy
5:1 to 10:1 ratio of linolenic:alpha-linolenic acid
Saturated fat: less than 7% of energy
Trans fats: reduced to the absolute minimum 35

36. Food Sources of Fat Visible fats Invisible fats Fats we add to foods
Butter, cream, mayonnaise, salad dressings
Invisible fats
Fats hidden within foods
Occur naturally or added during processing
Baked goods, dairy, meats, fast foods 36

37. Food Sources of Fat Beneficial fats
Omega-3 fatty acids may be low in diets
Fish, walnuts, soy, canola, flaxseed
Switching to more healthful fats without increasing total fat intake
Use olive or canola oil in place of butter or margarine
Select low-fat or nonfat dairy products 37

40. Food Sources of Fat Fat replacers Used to lower fat content of foods
Found in chips, cakes, cookies
May cause GI side effects in large amounts
Example: olestra (Olean)
Fats in Food 40

42. Cardiovascular Disease
Dysfunction of the heart or blood vessels
Can result in heart attack or stroke 42

43. Cardiovascular Disease
Risk factors for cardiovascular disease:
Being overweight
Physical inactivity
Smoking
High blood pressure
Diabetes mellitus
Inflammation 43

45. Cardiovascular Disease
Dietary fats increase blood lipids
Highly saturated and trans fat intakes increase blood cholesterol
Omega-3 fatty acids reduce inflammation and blood triglycerides 45

46. Cardiovascular Disease
Blood lipids include:
Chylomicrons—present only after a meal
Very-low-density lipoproteins (VLDL)
Low-density lipoproteins (LDL)
High-density lipoproteins (HDL)
Lipoproteins: VLDL, LDL, and HDL 46

48. Cardiovascular Disease
Diets high in saturated fats
Decrease the removal of LDLs from the blood
Increase blood cholesterol levels
Contribute to the formation of plaques that can block arteries 48

51. Cardiovascular Disease
Diets high in trans fatty acids:
Can raise blood levels of LDL-cholesterol as much as saturated fat
Are abundant in hydrogenated vegetable oils (margarine, baked goods, fried foods)
FDA requires that trans fatty acid content be listed on labels for conventional foods and some dietary supplements 51

52. Cardiovascular Disease
Lifestyle changes can prevent or reduce cardiovascular heart disease
Total fat intake: 20−35% total calories
Saturated fat: less than 7% total calories
Cholesterol: less than 300 mg per day
Trans fat: reduce to absolute minimum
Increase omega-3 fatty acids
Dietary fiber: 20−30 grams per day
Folate: 400 micrograms/day 52

53. Cardiovascular Disease
Lifestyle changes can prevent or reduce cardiovascular heart disease
Maintain normal blood glucose level
Eat throughout the day
No more than 2 alcoholic beverages per day for men and 1 drink per day for women
Maintain an active lifestyle
Maintain a healthful body weight
Decrease salt intake (DASH diet)
Fast Food Trends 53

54. Cardiovascular Disease
Medicines help reduce risk
Endogenous cholesterol synthesis inhibitors: statins
Bile acid sequestrants
Nicotinic acid 54