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Chapter 4 Lipids: Fats and Oils 1 Learning Objectives 1. 2. 3. 4. 5. 6. Describe lipids and list their functions in foods and in the body Describe the relationship between triglycerides and fatty acids Define saturated, monounsaturated, and polyunsaturated fats and list foods in which each one is found Describe trans fatty acids and give examples of foods in which they are found Identify the two essential fatty acids, list their functions in the body, and give examples of foods in which they are found Define cholesterol and lecithin, list their functions in the body, identify where they are found in the body, and give examples of foods in which they are found Learning Objectives (cont’d) 7. 8. 9. 10. 11. 12. Describe how fats are digested, absorbed, and metabolized Discuss the relationship between lipids and health conditions such as heart disease and cancer State recommendations for dietary intake of fat, saturated fat, trans fat, monounsaturated fat, polyunsaturated fat, and cholesterol Distinguish between the percentage of fat by weight and the percentage of kcalories from fat Calculate the percentage of kcalories from fat for a food item Discuss the nutrition and uses of milk, dairy products, and eggs on the menu Lipids Fats Oils Cholesterol Lecithin 4 Functions of Lipids Insulation Cushion around critical organs Provides energy (adipose cells = compact energy storage) Protein-sparing Part of all cell membranes Transport of fat-soluble vitamins Essential fatty acids 5 In food, fat enhances: Taste Smooth texture Flavor Creamy feeling Aroma Feeling full Crispness Juiciness Tenderness 6 A Triglyceride 7 Types of Fatty Acids Point of Unsaturation 8 Lecithin A phospholipid Vital component of cell membranes Acts as an emulsifier Triglycerides in Food Which groups contain the most triglycerides? Fruits and vegetables Breads, cereals, rice, pasta, and grains Dry beans and peas, nuts and seeds Meat, poultry, fish Dairy foods Fats, oils, and condiments All fats in foods contain a mixture of saturated and unsaturated fats. 10 3 Types of Triglycerides 1. Saturated triglycerides (saturated fat) ANIMAL FOODS Cheese Beef Whole milk Fats in baked goods Butter Coconut, palm kernel, and palm oils 11 3 Types of Triglycerides 2. Monounsaturated Fats Olive oil Canola oil Peanut oil Margarine made with canola oil or other highly monounsaturated fat Olive Oil 12 3 Types of Triglycerides 3. Polyunsaturated Fats Safflower oil Corn oil Soybean oil Sesame oil Sunflower oil Nuts and seeds 13 Trans Fatty Acids = Trans Fats Occur naturally at low levels in meat and dairy foods Trans fats we eat are often due to hydrogenation of vegetable oils to make shortening, margarine, and fats for frying Trans fats raise blood cholesterol levels as much as saturated fat 14 Main Contributors to Trans Fats in Diet Cakes, cookies, pies, bread, etc. Animal products Margarine Fried potatoes Potato chips, corn chips, popcorn Household shortening 15 Essential Fatty Acids Linoleic acid is an omega-6 fatty acid found in vegetable oils, whole grains, and vegetables. Alpha-linolenic acid is the leading omega-3 fatty acid found in food, and it is found in canola, flaxseed, soybean, walnut, and wheat germ oils. Ground flaxseed is rich in alphalinolenic, and walnuts are also a good source. Americans get more than enough linoleic, but not enough alpha-linolenic. 16 DHA and EPA The body converts alpha-linolenic into DHA and EPA (also omega-3s) but the process is very slow, resulting in little DHA/EPA. DHA and EPA are found in fatty fish such as salmon and mackerel – AHA recommends eating fatty fish twice/week. DHA and EPA are VERY heart healthy. Essential Fatty Acids (cont’d) Both EFAs: Are vital to normal growth and development in infants and children Maintain the structural parts of cell membranes Have a role in the proper functioning of the immune system DHA and EPA are especially important for proper brain and eye development during pregnancy and infancy 18 Cholesterol An odorless, white, waxy, powdery substance Cholesterol is present in every cell in your body. It is needed to make bile acids cell membranes many hormones (such as sex hormones) vitamin D. 19 Cholesterol (cont’d) Cholesterol is found only in foods of animal origin: egg yolks, meat, organ meats, poultry, fish, milk, and milk products. Lower-fat milk products contain less cholesterol than full-fat milk products. 20 Cholesterol (cont’d) 4 ounces of meat, poultry, or fish contains 100 mg of cholesterol (except for shrimp). We take in about 200 to 400 milligrams of cholesterol daily and the liver and body cells also make cholesterol (about 700 milligrams), therefore it is not an essential nutrient. Digestion, Absorption, & Metabolism Mouth – Lingual lipase Stomach – Gastric lipase Intestine Bile acids Pancreatic lipase Intestinal lipase Once absorbed, triglycerides are reformed 22 Lipoproteins Protein-coated packages that carry fat and cholesterol through the bloodstream Chylomicron Very low-density lipoprotein (VLDL) Low-density lipoprotein (LDL) High-density lipoprotein (HDL) 23 Lipids and Health Heart disease Too much circulating cholesterol leads to plaque and atherosclerosis – as arteries become narrowed, increased chance of heart attack and stroke Main source of cholesterol buildup: LDL 24 Lipids and Health (cont’d.) What affects blood cholesterol levels? Saturated fat, trans fat, and cholesterol in diet Mono- and polyunsaturated fat in diet Weight Physical activity Age and gender Heredity 25 Lipids and Cancer Cancer is the second leading cause of death in the U.S. Fat may be involved in certain cancers such as prostate cancer. 26 Dietary Recommendations for Fat No RDA or AI for total fat (except for infants), saturated fat, cholesterol, or trans fats. AMDR for total fat 1–3 years old 4–18 years old Over 18 years old 30-40% of kcal 25-35% of kcal 20-35% of kcal AI set for essential fatty acids DGA and AHA recommend 10% or less from sat. fat, less than 300 mg of cholesterol daily, and replace sat fats with poly and mono fats such as fish and nuts. If fat intake is higher than 30%, use monounsaturates. 27 Percentage of Kcal From Fat & Percentage of Fat By Weight Percentage of kcalories from fat 27 kcal from fat x 100 = 19 percent 140 kcal Percentage of fat by weight 28 Ingredient Focus: Milk, Dairy & Eggs Milk Cheese Eggs 29 Culinary Science Fat in milk is homogenized To make whipped cream, you need a cream with at least 30% fat What happens when you whip cream for too long? Milk, eggs, and cheese are generally cooked at low to moderate heat Culinary Science: Rancidity Deterioration of fat, resulting in undesirable flavors and odors Saturated fats are more resistant to rancidity than unsaturated fats Rancidity is hastened by heat and ultraviolet light To prevent rancidity, store fats and oils tightly sealed in cool, dark places 31 Food Facts: Oils & Margarines Butter and margarine must contain at least 80% fat by weight Types of oils Olive oil: extra virgin or virgin, pure, light Margarines vary by: Physical form Type of oil Percent fat by weight Hot Topic: Trans Fats in Restaurants Laws in certain cities have phased out trans fats in many restaurants Pros and cons Copyright ©2010 John Wiley & Sons, Inc. Clip art images may not be saved or downloaded and are only to be used for viewing purposes. 34