Chapter 4: The Lipids

Presented by Michelle Loy, MPH, MS, RD

Learning Objectives

• At the completion of this section, the students will be able to:• Describe the functions of triglycerides,

phospholipids, and cholesterol.• Differentiate the 3 types of fatty acids• Define trans fats and explain their

effect on human health• Outline the steps involved in fat

digestion, absorption, and transportation

• Discuss the roles of fats in the body and in food

• Discuss the relationship between lipids and health (cardiovascular disease, cancer, obesity)

• Review a diet and suggest modifications so that it would meet current recommendations for the types and amounts of fat.

Learning Objectives

• Define the types of essential fatty acids and their functions

• Differentiate between visible and invisible fats in food

• Identify major sources of saturated, monounsaturated, polyunsaturated, omega-6, omega-3, and trans fatty acids and cholesterol in the diet.

Learning Objectives

What Are Fats?

Types of Lipids -- Triglycerides

• Most commonly found in food and in body storage

• Properties determined by fatty acids they contain

Saturated vs UnsaturatedFatty acids

Different Unsaturated Fatty Acids: Essential Fatty Acids

• Must be consumed in the diet

• Linoleic acid (-6) and alpha-linolenic acid ( -3)

Different Unsaturated Fatty Acids

• The hydrogen atoms at the unsaturated region can be arranged in different positions:

• Cis • Trans

• Hydrogenation

Foods Contain Varying Amounts of Fatty Acids

Types of Lipids --

• Key role in structure of cell membranes

• Manufactured in our bodies so they are not required in our diet

Types of Lipids --

• Cholesterol:• Made only by animals in the liver• Component of cell membrane and myelin• Needed for synthesis of vitamin D, bile, and some

hormones

• Plant sterols and stanols• Naturally found in some vegetable

oils, nuts, seeds, legumes, grain products, fruits, and vegetables

• Have been added to common foods• Help lower LDL-cholesterol

• 2-3 g/d of plant sterols or stanols

Types of Lipids --

Digestion of Fats

Roles of fats in the body

• Energy

• Insulation

• Nerve cell transmissions

Roles of fat in food

• Nutrient

• Transport

• Appetite

• Flavor and texture

Recommendations

• The Acceptable Macronutrient Distribution Range (AMDR) for fat:• _________% of calories should be from

fat• Cholesterol <_____ mg/d for a

healthy adult population• <200 mg/d for adults with elevated

blood LDL-cholesterol levels

Recommendations

• The type of fat consumed is important.• Saturated fat should be no more than

___% of total calories.• Trans fatty acids should be reduced

to the absolute minimum.• Most fat in our diets should be from

monounsaturated fats.

• Dietary Guidelines• When selecting and preparing meat,

poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free.

• Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose products low in such fats and oils

Recommendations

• Mostly found in animal products• Fatty cuts of meat• Poultry with skin• Lard • Whole milk dairy products (whole or 2%

milk, yogurt, cheese, ice cream)• Butter • Tropical oils (palm, palm kernel, coconut)

Food Sources of Fat

Food Sources of Fat

• Found in greatest amounts in food from plants

• Olive, canola, sunflower, peanut oils

• Olives• Nuts • Avocados

• Found in great amounts in food from plants

• Safflower, canola, sunflower, corn, soybean, flaxseed, and cottonseed oil

• Nuts

Major sources of trans fats in the diet

• EPA and DHA• Seafood – fatty, coldwater fish

• Salmon, mackerel, herring• 12-14 oz of fish/week

• ALA• Flaxseeds, flaxseed oil • Walnuts• Soybean and canola oil (small amount)

Food Sources of Fat

Food Sources of Fat

• Dietary cholesterol• Only found in animal foods• Sources

• Egg yolk, beef, poultry, cheese, milk, shellfish, organ meat

Food Sources of Fat

• Fats we can see in our foods or knowingly add to foods

• Fats hidden in foods• Naturally occurring or added during

processing

Lipids and Health

• Too little fat:• Essential fatty acid deficiency

• Too much total fat and too much “bad” fat• Cardiovascular disease• Cancer• Obesity

Dietary Fat and Heart Disease

• Buildup of fatty material in the artery walls cause atherosclerosis

Risk factors for cardiovascular disease

Cardiovascular Disease

• Blood lipids include• Triglycerides• Chylomicrons• VLDLs – very low-

density lipoproteins• LDLs – low-density

lipoproteins• “bad cholesterol”

• HDLs – high-density lipoproteins

• “good cholesterol”

Dietary Factors That Promote Heart Disease

• Dietary Cholesterol• Gene-dependent

• Increases LDL cholesterol in the blood

• Increases blood LDL cholesterol levels• Lower HDL cholesterol levels

• Excess Energy• Increases body fat

Dietary Factors That Protect Against Heart Disease

-6 fatty acids• Lower both LDL and

HDL cholesterol

-3 fatty acids• Lower LDL cholesterol• Other benefits

• Monounsaturated fat• Decrease LDL

cholesterol

• Plant foods• Fiber and antioxidants

• B vitamins• Decrease blood

homocysteine level

• Moderate alcohol consumption

Dietary Fat and Cancer

• Diets high in fat and low in fiber and plant foods are correlated with the incidence of cancer.

• Breast cancer

• Colon cancer

Dietary Fat and Obesity

• A high-fat meal contains more kcalories than a low-fat meal of the same volume.

• Energy from fat is less satiating than energy from carbohydrates.

• It takes less energy for the body to use fat as an energy source.

• However, fat content is unlikely the reason for the high obesity rate in the U.S.

Reasons to keep fat intake low

• Diets lower in fat are generally lower in calories and thereby help achieve and maintain healthy body weight

• Diets low in saturated and trans fats reduce the risk of heart disease

• Diets lower in fat, particularly saturated fat, may lower the risks of some cancers

• Diets with fewer calories from fat have more room for health promoting foods

Translating recommendations into healthy diets

• Read food labels• Choose added fats carefully

• Limit amounts• Choose healthier fats

• Choose protein sources wisely• Substitute low-fat ingredients for high-fat

ingredients in recipes• Choose leaner cooking methods• Choose smaller portions of higher fat items• Reduce frequency of consumption of higher fat

items• Increase vegetables and fruits

How to Choose Fats Wisely

Assignment

• On at least one day this week:• Incorporate at least 1 source of

healthy fat• Reduce at least 1 source of unhealthy

fat