1 Chapter 4 Lipids: Fats and Oils. Learning Objectives 1. Describe lipids and list their functions in foods and in the body 2. Describe the relationship.

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Chapter 4

Lipids: Fats and Oils

Learning Objectives

1. Describe lipids and list their functions in foods and in the body2. Describe the relationship between triglycerides and fatty acids3. Define saturated, monounsaturated, and polyunsaturated fats

and list foods in which each one is found4. Describe trans fatty acids and give examples of foods in which

they are found5. Identify the two essential fatty acids, list their functions in the

body, and give examples of foods in which they are found6. Define cholesterol and lecithin, list their functions in the body,

identify where they are found in the body, and give examples of foods in which they are found

Learning Objectives (cont’d)

7. Describe how fats are digested, absorbed, and metabolized

8. Discuss the relationship between lipids and health conditions such as heart disease and cancer

9. State recommendations for dietary intake of fat, saturated fat, trans fat, monounsaturated fat, polyunsaturated fat, and cholesterol

10. Distinguish between the percentage of fat by weight and the percentage of kcalories from fat

11. Calculate the percentage of kcalories from fat for a food item

12. Discuss the nutrition and uses of milk, dairy products, and eggs on the menu

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Lipids

FatsOilsCholesterolLecithin

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Functions of Lipids

Insulation Cushion around critical organs Provides energy (adipose cells = compact

energy storage) Protein-sparing Part of all cell membranes Transport of fat-soluble vitamins Essential fatty acids

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In food, fat enhances:

Taste Flavor Aroma Crispness Juiciness Tenderness

Smooth texture Creamy feeling Feeling full

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A Triglyceride

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Types of Fatty Acids

Point of

Unsaturation

Lecithin

A phospholipid Vital component

of cell membranes

Acts as an emulsifier

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Triglycerides in Food

Which groups contain the most triglycerides? Fruits and vegetables Breads, cereals, rice, pasta, and grains Dry beans and peas, nuts and seeds Meat, poultry, fish Dairy foods Fats, oils, and condiments

All fats in foods contain a mixture of saturated and unsaturated fats.

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3 Types of Triglycerides

1. Saturated triglycerides (saturated fat) ANIMAL FOODS

Cheese Beef Whole milk Fats in baked goods Butter Coconut, palm

kernel, and palm oils

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2. Monounsaturated Fats

Olive oil Canola oil Peanut oil Margarine made with

canola oil or other highly monounsaturated fat

Olive Oil

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3. Polyunsaturated Fats Safflower oil Corn oil Soybean oil Sesame oil Sunflower oil Nuts and seeds

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Trans Fatty Acids = Trans Fats

Occur naturally at low levels in meat and dairy foods

Trans fats we eat are often due to hydrogenation of vegetable oils to make shortening, margarine, and fats for frying

Trans fats raise blood cholesterol levels as much as saturated fat

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Main Contributors to Trans Fats in Diet

Cakes, cookies, pies, bread, etc. Animal products Margarine Fried potatoes Potato chips, corn chips, popcorn Household shortening

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Essential Fatty Acids

Linoleic acid is an omega-6 fatty acid found in vegetable oils, whole grains, and vegetables.

Alpha-linolenic acid is the leading omega-3 fatty acid found in food, and it is found in canola, flaxseed, soybean, walnut, and wheat germ oils. Ground flaxseed is rich in alpha-linolenic, and walnuts are also a good source.

Americans get more than enough linoleic, but not enough alpha-linolenic.

DHA and EPA

The body converts alpha-linolenic into DHA and EPA (also omega-3s) but the process is very slow, resulting in little DHA/EPA.

DHA and EPA are found in fatty fish such as salmon and mackerel – AHA recommends eating fatty fish twice/week.

DHA and EPA are VERY heart healthy.

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Essential Fatty Acids (cont’d)

Both EFAs: Are vital to normal growth and development in

infants and children Maintain the structural parts of cell

membranes Have a role in the proper functioning of the

immune system DHA and EPA are especially important for

proper brain and eye development during pregnancy and infancy

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Cholesterol

An odorless, white, waxy, powdery substance Cholesterol is present in every cell in your

body. It is needed to make bile acids cell membranes many hormones (such as sex hormones) vitamin D.

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Cholesterol (cont’d)

Cholesterol is found only in foods of animal origin: egg yolks, meat, organ meats, poultry, fish, milk, and milk products. Lower-fat milk products contain less cholesterol than full-fat milk products.

Cholesterol (cont’d)

4 ounces of meat, poultry, or fish contains 100 mg of cholesterol (except for shrimp).

We take in about 200 to 400 milligrams of cholesterol daily and the liver and body cells also make cholesterol (about 700 milligrams), therefore it is not an essential nutrient.

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Digestion, Absorption, & Metabolism

Mouth – Lingual lipase Stomach – Gastric lipase Intestine

Bile acids Pancreatic lipase Intestinal lipase

Once absorbed, triglycerides are reformed

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Lipoproteins

Protein-coated packages that carry fat and cholesterol through the bloodstream

Chylomicron

Very low-density lipoprotein (VLDL)

Low-density lipoprotein (LDL)

High-density lipoprotein(HDL)

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Lipids and Health

Heart disease Too much circulating cholesterol leads to

plaque and atherosclerosis – as arteries become narrowed, increased chance of heart attack and stroke

Main source of cholesterol buildup: LDL

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Lipids and Health (cont’d.)

What affects blood cholesterol levels? Saturated fat, trans fat, and cholesterol in diet Mono- and polyunsaturated fat in diet Weight Physical activity Age and gender Heredity

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Lipids and Cancer

Cancer is the second leading cause of death in the U.S.

Fat may be involved in certain cancers such as prostate cancer.

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Dietary Recommendations for Fat

No RDA or AI for total fat (except for infants), saturated fat, cholesterol, or trans fats.

AMDR for total fat 1–3 years old 30-40% of kcal 4–18 years old 25-35% of kcal Over 18 years old 20-35% of kcal

AI set for essential fatty acids DGA and AHA recommend 10% or less from sat. fat,

less than 300 mg of cholesterol daily, and replace sat fats with poly and mono fats such as fish and nuts.

If fat intake is higher than 30%, use monounsaturates.

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Percentage of Kcal From Fat &Percentage of Fat By Weight

Percentage of kcalories from fat 27 kcal from fat x 100 = 19 percent

140 kcal Percentage of fat by weight

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Ingredient Focus: Milk, Dairy & Eggs

Milk

Cheese

Eggs

Culinary Science

Fat in milk is homogenized To make whipped cream, you need a cream

with at least 30% fat What happens when you whip cream for too

long? Milk, eggs, and cheese are generally cooked

at low to moderate heat

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Culinary Science: Rancidity

Deterioration of fat, resulting in undesirable flavors and odors

Saturated fats are more resistant to rancidity than unsaturated fats

Rancidity is hastened by heat and ultraviolet light

To prevent rancidity, store fats and oils tightly sealed in cool, dark places

Food Facts: Oils & Margarines

Butter and margarine must contain at least 80% fat by weight

Types of oils Olive oil: extra virgin or virgin, pure, light

Margarines vary by: Physical form Type of oil Percent fat by weight

Hot Topic: Trans Fats in Restaurants

Laws in certain cities have phased out trans fats in many restaurants

Pros and cons

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Copyright ©2010 John Wiley & Sons, Inc.

1 Chapter 4 Lipids: Fats and Oils. Learning Objectives 1. Describe lipids and list their functions in foods and in the body 2. Describe the relationship.

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