Chapter FourThe Lipids: Fats & OilsNUT SCI 242 Food & Nutritional Health Karen Lacey, MS ,RD, CD

What are Lipids?A family of compounds that includesTriglycerides (fats & oils)Fats: lipids that are solid at room temperatureOils: lipids that are liquid at room temperaturePhospholipidsSterols (cholesterol).

I. A Primer on FatsThe Functions of Fat in the BodyEnergy source esp. for musclesServes as an energy reserve1# body fat contains 3500 kcal30-50# of stored fat

ContdMajor component of cell membranesNourishes skin & hairInsulates the body from temperature extremesCushion the vital organs to protect them from shock

B. The Functions of Fat in FoodProvide calories (9 per gram)Provide satietyCarry fat-soluble vitamins & essential fatty acidsContribute aroma & flavor

Lipid TerminologyTriglycerides: the major class of dietary lipids, including fats & oilsMade 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

ContdPhospholipids: 2nd of three main classes of lipids similar to a triglyceride, but contains phosphorousSterols3rd of three main classes of lipids; Cholesterol one of the sterolsmanufactured in the body for a variety of purposes

ContdFatty 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

II. A Closer View of FatsChain Length (number of carbons linked together)Shorter = more soluble in waterSaturated vs. Unsaturated (number of hydrogens the chain is holding)Maximum = saturatedUnsaturated = one or more is missingPoint of unsaturation = site where hydrogen is missing

ContdSaturated 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

ContdUnsaturated fatty acid: a fatty acid with one or more points of unsaturation.Found in foods from both plants & animal sourcesMonounsaturated fatty acids (one double bond)Polyunsaturated fatty acids (two or more)

Contd Monounsaturated fatty acid: also called a MUFA; a fatty acid containing one point of unsaturationFound mostly in vegetable oils such as olive, canola & peanut

ContdPolyunsaturated fatty acids: also called a PUFA; a fatty acid in which two or more point of unsaturation occurFound in nuts, vegetable oils such as safflower, sunflower and soybean, and in fatty fish

B. Essential Fatty AcidsThe body can synthesize all of the fatty acids it needs from carbohydrates, fat or protein except for two:Linoleic acidLinolenic acidPUFAsFound in plant & fish oils

Omega - 6 versus Omega - 3Omega 6LinoleicOmega 3 LinolenicCold water fishHelp dissolve blood clotsLower blood pressureDilate the arteries

Characteristics of Fats in FoodsLiquid vs SolidMore saturated a fat is, the more solid it is at room temperatureMore unsaturated a fat is, the more liquid it is at room temperature

III. Characteristics of Fats in FoodsHydrogenationThe process of adding hydrogen to unsaturated fat to make it more solid and more resistant to chemical changes such as spoilingIncreasing a fats saturation can cause a fat to lose its unsaturated health benefits

C. Trans-Fatty AcidsFormed when margarine is processedHydrogen molecules are on opposite sides of point of unsaturationPartially hydrogenated vegetable oilLink between trans fatty acids and heart diseaseTable 4-3, page 107Keep to minimum

V. PhospholipidsA lipid consisting of a water-soluble head and a fat-soluble tailContain phosphorousComponent of cell membranesServe as emulsifiers (allow fats and water to mix and travel in and out of cells into watery fluid on both sides)

ContdLecithin is a common phospholipidOften used as an emulsifier in foods such as margarine, chocolate & salad dressings

V. Cholesterol a SterolFound only in animal productsAlso made & used in the body:Structure of cell membranesUsed to make bile for digestion Bile: a mixture of compounds, made by the liver, stored in the gallbladder, & secreted into the small intestineEmulsifies lipids to prepare them for enzymatic digestion & helps transport them into the intestinal wall cells

ContdUsed to make the sex hormones estrogen & testosteroneMade into vitamin D with the help of sunlightDeposited in the artery walls leading to plaque buildup & heart disease

VI. How the Body Handles Fat

DigestionEmulsificationAbsorption

VII. Lipids & HealthGood vs. Bad Cholesterolhttp://www.americanheart.org/http://www.mayohealth.org/http://www.fda.gov/

B. Lowering Blood Cholesterol LevelsEat no more than 30% of calories from fatEat no more than 8-10% of calories from saturated fatEat no more than 10% of calories from PUFAsMUFAs should make up 10-15% of total caloriesLimit daily cholesterol intake to no more than 300 milligrams

VIII. Fat in the DietFood Guide Pyramid3 groups traditionally account for nine-tenths of the fat in the U.S. dietFats, oils & sweets groupMeat, poultry, fish, dry beans, eggs & nut groupMilk, yogurt & cheese groupMost of the fat in our diets comes from animal products

B. Fat SubstitutesCarbohydrate-basedHelp retain moisture to maintain the juiciness or creaminess that is lost with fat reductionCarrageenan, fruit purees, gelatin, gums, starches & products made from fiberProtein-basedProteins are cooked & blended to form tiny round particles that trap water to maintain the mouth feel of fatWhey protein concentrate (Dairy-Lo), or milk & egg white protein (Simplesse)

Contd Fat-basedAre either only partially digestible or completely undigestible to prevent absorption of fatCaprenin (substitute for cocoa butter in candy), Salatrim (found in low fat baking chips), and olestra (often found in fat free potato chips)

C. At the Grocery StoreRead labels to determine both the amounts & types of fat contained in foods

D. In the KitchenUse canola & olive oil for baking & cookingPrepare lean cuts of meatBake, broil & steam instead of fryingUse low-fat or fat-free dairy products & dressingsSeason with herbs & spices rather than with fatsIncorporate plant-based protein sources such as soy & legumes

E. At the TableEat more fresh fruits & vegetablesUse jam instead of butterLimit use of high-fat condiments including mayo, butter & sour cream or use low-fat varietiesUse mostly monounsaturated vegetable oils such as olive or canolaEat fewer high-fat desserts

F. Recipe ModificationEgg whitesFat-free evaporated milkFat-free sour creamFruit purees Fat-free cream cheeseOils

IX. Diet & Heart DiseaseRisk FactorsHigh cholesterolHigh blood pressureSmokingDiabetesLack of exerciseStress ObesityUnhealthy dietAge GenderGenetics

ContdWays to Reduce RiskLimit intake of cholesterol & saturated fatQuit smokingMaintain a healthy weightEat high fiber foodsIncrease physical activityIncrease fruit & vegetable consumptionLimit alcohol consumption