Chapter 3 Fats Chapter 3 Lesson 3.1 Key Concepts Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material. Foods from animal and plant sources supply distinct forms of fat that affect health in different ways. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health. The Nature of Fats Dietary importance Concentrated fuel for energy Classes of fats Lipids Glycerides Triglycerides Fatty acids Lipoproteins Fatty Acids Saturated fatty acids Filled or saturated with hydrogen
Unsaturated fatty acids Not completely filled with hydrogen Less heavy, less dense Monounsaturated: one unfilled spot Polyunsaturated: two or more unfilled spots Essential Fatty Acids Polyunsaturated fatty acids Linoleic (omega-6) Alpha-linolenic (omega-3) Types of Fatty Acids Phospholipids Triglyceride derivative: third fatty acid replaced by phosphate group Partially hydrophobic, partially hydrophilic Major constituents in cell membranes Allow transport of fats through bloodstream Phospholipid Bilayer Cholesterol Not a fat A fat-related compound From animal foods Egg yolks
Liver, kidney Meats Synthesized in the liver Diet should be low in cholesterol Linked with heart disease Functions of Fat in Foods Fat in foods provide: Energy Essential nutrients Flavor and satisfaction Fat substitutes are not absorbed and therefore do not provide energy or essential nutrients but may provide flavor and satisfaction Functions of Fat in the Body Adipose tissue Protects organs Helps regulate temperature Cell membrane structure Forms part of cell membrane Helps transport nutrients across cell membranes Food Sources of Fat Animal fats Plant fats
Hydrogenated fats Commercial fat products raise health concerns Cis form Trans form Food industry now offers trans-free products Trans Fatty Acid Food Label Information Calories from fat Calories from saturated fat* Total fat Saturated fat Polyunsaturated fat* Monounsaturated fat* Cholesterol *Voluntary information Characteristics of Food Fat Sources Visible fat Invisible Fat FDA Health Claims Link one or more dietary components to the reduced risk of a specific disease Fat and cancer
Saturated fat and cholesterol and heart disease Chapter 3 Lesson 3.2 Key Concepts Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health. Dietary Fat and Health The American diet is high in fat. Excess calories are stored as fat. Animal food sources contribute to excess cholesterol and saturated fat in the diet. A decrease in saturated fat reduces serum total cholesterol. Monounsaturated fats reduce LDL cholesterol when substituted for saturated fat. Digestion of Fats Mouth Stomach Small intestine Bile from the gallbladder Enzymes from the pancreas Enzymes from the small intestine Absorption Dietary Fat Requirements
Healthy diet guidelines: Stress the health benefits of a diet low in fat, saturated fat, and cholesterol Recommend that the fat content should not exceed 20% to 35% of total kilocalories Less than 10% of kilocalories should be from saturated fat Dietary cholesterol should be limited to 300 mg/day Dietary Reference Intakes Linoleic acid: 17 g/day for men 12 g/day for women Linolenic acid: 1.6 g/day for men 1.1 g/day for women Current U.S. diet at ratio of 8:1 to 12:1 Recommended ratio of 2:1 to 3:1 Dietary Guidelines for Americans Control saturated fat and cholesterol Use only lean cuts of all meats; use more poultry and seafood Limit eggs to two or three per week Use low-fat or fat-free milk and milk products Avoid adding too much fat in food preparation Summary
Fat is an essential body nutrient Fat serves as a back-up storage fuel for carbohydrate Fat supplies structural material for cell walls, protective padding for vital organs, insulation to maintain body temperature, and covering for nerve cells Summary, cont d Classes of fat include lipids, triglycerides, fatty acids, and lipoproteins Fatty acids can be saturated or unsaturated Essential fatty acids are necessary to aid in tissue strength, cholesterol metabolism, muscle tone, blood clotting, and heart action Summary, cont d Cholesterol is a sterol that is vital in human metabolism Cholesterol is only found in animal foods Digestion of fat includes digestive agents such as bile and pancreatic lipase Fatty acids and glycerides are incorporated into chylomicrons and absorbed via the lymphatic system into the bloodstream