Dietary Fats & Lipids: Impacts on Health

1. Overview of dietary fats and lipid, in relation to rancidity and per oxidation

2. What are Lipids? • A family of compounds that includes • Triglycerides (fats & oils) • Fats: lipids that are solid at room temperature • Oils: lipids that are liquid at room temperature • Phospholipids • Cell membrane, lipid bilayers, amphipathic • Sterols (cholesterol). • Steroid alcohol

4. I. A Primer on Fats • The Functions of Fat in the Body • Energy source esp. for muscles • Serves as an energy reserve • 1# body fat contains 3500 kcal • 30-50%- of stored fat

5. Major component of cell membranes • Nourishes skin & hair • Insulates the body from temperature extremes • Cushion the vital organs to protect them from shock

7. B. The Functions of Fat in Food • Provide calories (9 per gram) • Provide satiety • Carry fat-soluble vitamins & essential fatty acids • Contribute aroma & flavor

9. Lipid Terminology • Triglycerides: the major class of dietary lipids, including fats & oils • Made up of 3 units known as fatty acids and 1 unit called glycerol (backbone) • Comprise about 95% of lipids in food and the human body

12. Phospholipids: • 2nd of three main classes of lipids • similar to a triglyceride, but contains phosphorous • Sterols • 3rd of three main classes of lipids; • Cholesterol • one of the sterols • manufactured in the body for a variety of purposes

13. Fatty acids: • basic units of fat composed of chains of carbon atoms • an acid group at one end and hydrogen atoms attached all along their length • If not attached with other molecule---free fatty acid • When metabolized yield ATP • Heart and muscle---prefer fatty acid for fuel • Without double bond---saturated • With double bond---unsaturated

15. II. A Closer View of Fats • Chain Length (number of carbons linked together) • Shorter = more soluble in water • Saturated vs. Unsaturated (number of hydrogens the chain is holding) • Maximum = saturated • Unsaturated = one or more is missing • Point of unsaturation = site where hydrogen is missing

16. Saturated fatty acid: a fatty acid carrying the maximum possible number of hydrogen atoms • Animal foods such as meat, poultry and full-fat dairy products • Tropical oils such as palm and coconut

18. Unsaturated fatty acid: a fatty acid with one or more points of unsaturation. • Found in foods from both plants & animal sources • Monounsaturated fatty acids (one double bond) • Polyunsaturated fatty acids (two or more)

19. Monounsaturated fatty acid: also called a MUFA; a fatty acid containing one point of unsaturation • Found mostly in vegetable oils such as olive, canola & peanut

21. Polyunsaturated fatty acids: also called a PUFA; a fatty acid in which two or more point of unsaturation occur • Found in nuts, vegetable oils such as safflower, sunflower and soybean, and in fatty fish

22. B. Essential Fatty Acids • The body can synthesize all of the fatty acids it needs from carbohydrates, fat or protein except for two: • Linoleic acid • Linolenic acid • PUFAs • Found in plant & fish oils Deficiency causes scaly dermatitis visual and neurologic abnormality

24. Omega - 6 versus Omega - 3 Omega – 6 • Linoleic Omega – 3 • Linolenic • Cold water fish • Help dissolve blood clots • Lower blood pressure • Dilate the arteries

26. Characteristics of Fats in Foods • Liquid vs Solid • More saturated a fat is, the more solid it is at room temperature • More unsaturated a fat is, the more liquid it is at room temperature

28. III. Characteristics of Fats in Foods • Hydrogenation • The process of adding hydrogen to unsaturated fat to make it more solid and more resistant to chemical changes such as spoiling • Increasing a fat’s saturation can cause a fat to lose its unsaturated health benefits

30. C. Trans-Fatty Acids • The adjacent two hydrogen atoms lie on opposite sides of the chain. • “Partially hydrogenated vegetable oil” • Link between trans fatty acids and heart disease • ↑ serum LDL, ↑ risk of CHD • High in baked ones, fried food esp deep fried

33. V. Phospholipids • A lipid consisting of a water-soluble head and a fat-soluble tail • Contain phosphorous • Component of cell membranes • Serve as emulsifiers (allow fats and water to mix and travel in and out of cells into watery fluid on both sides)

35. Lecithin is a common phospholipid • Often used as an emulsifier in foods such as margarine, chocolate & salad dressings

36. V. Cholesterol – a Sterol • Found only in animal products • Also made & used in the body: • Structure of cell membranes • Used to make bile for digestion • Bile: a mixture of compounds, made by the liver, stored in the gallbladder, & secreted into the small intestine • Emulsifies lipids to prepare them for enzymatic digestion & helps transport them into the intestinal wall cells

37. Used to make the sex hormones estrogen & testosterone • Made into vitamin D with the help of sunlight • Deposited in the artery walls leading to plaque buildup & heart disease

40. VI. How the Body Handles Fat • Digestion • Emulsification • Absorption

50. B. Lowering Blood Cholesterol Levels • Eat no more than 30% of calories from fat • Eat no more than 8-10% of calories from saturated fat • Eat no more than 10% of calories from PUFAs • MUFAs should make up 10-15% of total calories • Limit daily cholesterol intake to no more than 300 milligrams