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

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