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