Transcript
Chapter 5The Lipids: Fats, Oils, Phospholipids, and
Sterols
Introduction
• Diet moderate in fats– Lipids are necessary and valuable– Lipids can harm health
• Three classes of lipids– Triglycerides – Phospholipids– Sterols
Usefulness of Fats in the Body
• Chief storage form of energy– Provides most energy for body’s work
• Adipose tissue– Secretes hormones
• Purposes of fat– Shock absorbers, insulation, cell membranes
• Fat-soluble substances
A Fat Cell
Usefulness of Fats in Food
• People naturally like high-fat foods– Aromas– Flavors – Tenderness– Satiety
Triglycerides: Fatty Acids and Glycerol
• Triglycerides– Glycerol backbone– Three fatty acids
• Fatty acid differences– Chain length– Saturation
• Animal species make triglycerides
Saturated Versus Unsaturated Fatty Acids
• Saturation– Hydrogen atoms
• Levels of saturation– Saturated– Unsaturated• Polyunsaturated• Monounsaturated
Three Types of Fatty Acids
Saturated Versus Unsaturated Fatty Acids
• Melting point– More unsaturated,
more liquid• Fat hardness– Softer generally is
healthier• Sources of fatty acids– Heart disease
Fatty Acid Composition of Common Food Fats
Phospholipids and Sterols
• Phospholipids– Glycerol, two fatty acids, and a phosphorus
molecule• Soluble in water and fat
– Emulsifier • Sterols– Roles in the body– Plant sterols
Digestion and Absorption of Fats• Digestion– Stomach– Small intestine• Bile • Pancreas
Digestion and Absorption of Fats
• Absorption– Fatty acids split from glycerol• Fatty acids, phospholipids, and monoglycerides
– Bile shuttles lipids across mucus layer– Efficiency of absorption process• Speed of digestion
The Process of Lipid Digestion and Absorption
Transport of Fats
• Glycerol and shorter-chain fatty acids– Bloodstream
• Larger lipids– Protein carriers– Released into lymph– Chylomicrons
Storing and Using the Body’s Fat
• Body conserves fat molecules– Fat depots– Excess carbohydrate
• Call for energy– Dismantle stored triglycerides• Release fatty acids into blood
– Carbohydrate’s role• How to use more fat for energy…
Glucose to Fat
Dietary Fat, Cholesterol, and Health
• Heart and artery disease– Saturated and trans fats– Beneficial fats
• Cancer– Diet high in saturated fats
• Obesity– Overconsumption of calories
Recommendations for Lipid Intakes
• Some fat in the diet is essential• Healthy range of fat intakes– DRI• 20 to 35 percent of daily energy
– Fats to keep low• Essential fatty acids
Lipoproteins and Heart Disease Risk
• Lipoprotein movement in the body– Liver
• Types of lipoproteins– Chylomicrons– Very-low-density lipoproteins (VLDL)– Low-density lipoproteins (LDL)– High-density lipoproteins (HDL)
Lipoproteins
Lipoproteins and Heart Disease Risk
• LDL and HDL difference– Size and density– Delivery and scavenging– Inflammation– Heart attack risk
• Oxidation of LDL– Phytochemicals
Food Cholesterol and Blood Cholesterol
• Saturated and trans fats– CVD risk indicators
• Dietary cholesterol– Genetic inheritance– Moderation is key
Recommendations Applied
• Heart disease– Leading cause of death among Americans
• Lower LDL– Dietary tactics• Trim saturated and trans fats from diet
• Raise HDL– Physical activity• Benefits for heart health
Food Fat, Saturated Fat, and Calories
The Need for Essential Fatty Acids
• Essential fatty acids– Linoleic acid and
linolenic acid• Functions– Eicosanoids
• DRI recommendations• Deficiencies
Omega-6 and Omega-3 Fatty Acid Families
• Linoleic– Omega-6 fatty acid– Arachidonic acid
• Linolenic acid– Omega-3 fatty acid– DHA and EPA• Heart disease• Brain function and vision• Inflammation
Recommendations for Omega-3 Fatty Acid Intake
• Competition for metabolic enzymes• Consumption levels– Lacking omega-3 fatty acids
• Fish oil supplements– Health concerns with fish oil supplements
• Omega-3 enriched foods • Flaxseed
Food Sources of Omega-6 and Omega-3 Fatty Acids
Seafood Safety – Balancing Risks and Benefits
• Safe consumption levels• Mercury– Methylmercury– Damage to the body
• Cooking methods of fish• Benefits outweigh risks
Mercury in Fish Species
Effects of Processing on Unsaturated Fats
• Hydrogenation– Effects on fats
• Oxidation of unsaturated oils• Hydrogenation of oils– Benefits of hydrogenation
• Nutrient losses • Alternatives to hydrogenation
Hydrogenation Yields Both Saturated and Trans-Fatty Acids
Effects of Processing on Unsaturated Fats
• Trans-fatty acids– Polyunsaturated fats• Change in chemical structure
• Health effects– LDL and HDL cholesterol– Similarities with saturated fat
• Trans fat in foods
Fat in the Diet
• Essential fat– 20% of calories from unsaturated fats
• Visible vs. invisible fat• Added fats– Majority are invisible fats
Fat in the Diet
• Meat, poultry, fish, dried peas & beans, eggs, & nuts– Four categories for meat– Limit intake to 5 to 7 ounces per day– Choosing low-fat meats• Ground turkey or chicken vs. beef
• Milk, yogurt, and cheese– Foods not included in this category
• Grains
Calories, Fat, and Saturated Fat in Cooked Ground Meat Patties
Lipids in Milk, Yogurt, and Cheese
Lipids in Bread, Cereal, Rice, and Pasta
Defensive Dining
• Portion sizes• In the grocery stores• Fat replacers & artificial fats– Olestra– “Fat-free” options
• Cooking at home
Substitute Ingredients to Lower Saturated Fat Intakes
Good Fats and Bad Fats – Which are Which?
Objectives to “Low-Fat” Guidelines
• Problems with low-fat diets• Groups who benefit from low-fat diets– Mediterranean-type diets
• New guidelines– Up to 35 percent of total calories
High-Fat Foods and Heart Health
• Olive oil– Potential health
benefits– Darker the better
(extra virgin)• Canola oil
High-Fat Foods and Heart Health
• Mediterranean diet– Whole foods– Dietary focus– Fish– Nuts• Walnuts • Almonds• Potential benefits
High-Fat Foods and Heart Health
• Butter or margarine– Read labels– Low saturated fat and trans fat levels– Plant-enriched margarines• Drawbacks
• Fats to avoid– Choose carefully among high-fat foods
Impact of Change in Saturated Fatty Acid Intake on Blood LDL Cholesterol and Heart
Disease Risk
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