The Lipids: Fats, Oils, Phospholipids, and Sterols Chapter 5

Learning Objectives Identify the role of lipids in both the body and food, and explain why some amount of fat is necessary in the diet. Compare and contrast the chemical makeup and physical properties of saturated fats, polyunsaturated fats, monounsaturated fats, and phospholipids.

Learning Objectives Describe how and where dietary lipids are broken down and absorbed during digestion and how they are transported throughout the body. Describe the body’s mechanisms for fat storage and use of body fat, including the role of carbohydrate in fat metabolism.

Learning Objectives Describe the relationships between lipoproteins and disease risks, and explain how various fats and cholesterol in food affect cholesterol in the blood. Describe the roles of omega-3 and omega-6 fatty acids in the body, and name important food sources of each. Describe the formation and structure of a trans-fatty acid.

Learning Objectives Develop a diet plan that provides enough of the right kinds of fats within caloric limits. Identify at least 10 ways to reduce solid fats in an average diet. Discuss evidence for the benefits and drawbacks of specific dietary fats in terms of their effects on human health.

Introducing the Lipids Diet moderate in fats Lipids are necessary and valuable Lipids can harm health Three classes of lipids Triglycerides Phospholipids Sterols

The Usefulness of Fats

How Are Fats Useful to the Body? Chief storage form of energy Provides most energy for body’s work Adipose tissue Secretes hormones Fat storage efficiency Purposes of fat Shock absorbers, insulation, cell membranes Transport and raw material

A Fat Cell

How Are Fats Useful in Food? Concentrated calorie source Lots of energy in small packages Fat-soluble nutrients Vitamins Essential fatty acids

How Are Fats Useful in Food? Sensory qualities Aromas Flavors Tenderness Satiety Slows down food movement

Triglycerides: Fatty Acids and Glycerol Glycerol backbone Three fatty acids Fatty acid differences Chain length Saturation Animal species

Saturated vs. Unsaturated Fatty Acids Saturation Hydrogen atoms Levels of saturation Saturated Unsaturated Polyunsaturated Monounsaturated

Three Types of Fatty Acids

Saturated vs. Unsaturated Fatty Acids Melting point More unsaturated, more liquid Fat hardness Softer generally is healthier Sources of fatty acids

Fatty Acid Composition of Common Food Fats

Phospholipids and Sterols Glycerol, two fatty acids, and a phosphorus molecule Soluble in water and fat Emulsifier Sterols Rings of carbon Cholesterol roles in the body Plant sterols

Lipids in the Body Digestion Stomach Small intestine Bile Pancreas

Lipids in the Body 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 Larger lipids 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 in fat breakdown

Glucose to Fat

Dietary Fat, Cholesterol, and Health Heart and artery disease Saturated and trans fats Beneficial fats Refined carbohydrates Not just a ‘man’s disease’ Obesity Overconsumption of calories

Recommendations for Lipid Intakes Some fat in the diet is essential Essential fatty acids Healthy range of fat intakes DRI 20 to 35 percent of daily energy Fats to keep low U.S. fat intakes Too little lipid

Lipid Intake Recommendations for Healthy People

Sources of Solid Fats in the U.S. Diet

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 Cholesterol testing

Food Cholesterol and Blood Cholesterol Saturated and trans fats CVD risk indicators Dietary cholesterol Guidelines Sources Genetic inheritance Moderation is key

Recommendations Applied Heart disease Leading cause of death among Americans Lower LDL Trim saturated and trans fats from diet Raise HDL Physical activity Benefits for heart health

Cutting Solid Fats Cuts Calories and Saturated Fat

Essential Polyunsaturated Fatty Acids Essential fatty acids Linoleic acid and linolenic acid Functions Eicosanoids Deficiencies

Omega-6 and Omega-3 Fatty Acid Families Linoleic Omega-6 fatty acid Arachidonic acid Linolenic acid DHA and EPA Heart disease Cancer prevention Cell membranes Brain function and vision

Where Are the Omega-3 Fatty Acids in Foods? Seafood Special populations Children Pregnant and lactating women Fish oil supplements Omega-3 enriched foods Meats

Food Sources of Omega-6 and Omega-3 Fatty Acids

Weighing Seafood’s Risks and Benefits Finding the EPA and DHA Toxins Mercury Methylmercury Damage to the body Cooked vs. raw Farm fresh fish

Seafood Species – EPA/DHA and Mercury Contents

The Effects of Processing on Unsaturated Fats Hydrogenation Effects on fats Oxygen damage of unsaturated oils Hydrogenation of oils Benefits of hydrogenation Nutrient losses Alternatives to hydrogenation

Hydrogenation Yields Both Saturated and Trans-Fatty Acids

The Effects of Processing on Unsaturated Fats Formation of trans-fatty acids Polyunsaturated fats Change in chemical structure Health effects LDL and HDL cholesterol Similarities with saturated fat Swapping trans fats for saturated fats Trans fat in foods

Fat in the Diet Essential fat Replace fats instead of adding fats 20% of calories from unsaturated fats Replace fats instead of adding fats Visible vs. invisible fat Added fats Majority are invisible fats

Fat in the Diet Fats in protein foods Milk and milk products Grains Four categories for meat Limit intake to 5 to 7 ounces per day Choosing low-fat meats Ground turkey or chicken vs. beef Milk and milk products Foods not included in this category Grains

Calories, Fat, and Saturated Fat in Cooked Ground Meat Patties

Lipids in Milk and Milk Products

Lipids in Grains

Defensive Dining Reading ingredient lists In the grocery stores Margarines Unsaturated oils Fat replacers & artificial fats Olestra “Fat-free” options Revamp recipes

Solid Fat Ingredients Listed on Labels

Defensive Dining Fast food choices Change your habits Suggested changes Small changes reap big rewards

Good Fats, Bad Fats – U.S. Guidelines and the Mediterranean Diet Controversy 5

Objections to “Low-Fat” Guidelines Problems with low-fat diets May not be low in calories May still increase risk for heart disease May exclude nutritious foods Research on high-fat diets Mediterranean-type diet Current guidelines Up to 35 percent of total calories “Wise-fat” approach

High-Fat Foods of the Mediterranean Diet Olive oil Potential health benefits Darker the better (extra virgin) Cautions Calories Not a ‘magic’ potion

High-Fat Foods of the Mediterranean Diet Features of diet Whole foods Dietary focus Fatty fish Nuts Walnuts Almonds Potential benefits

A Mediterranean Diet Pyramid

Fats to Avoid: Saturated and Trans Fats Saturated fat Number-one dietary determinant of LDL Recommended diet composition Health is synergy Whole foods diet and lifestyle Choose wisely among fats

Mediterranean-Style Substitutions