The Lipids: Fats & Oils

What are Lipids?

A family of compounds that includes– Triglycerides (fats & oils)

Fats: lipids that are solid at room temperature

Oils: lipids that are liquid at room temperature

– Phospholipids– Sterols (cholesterol).

I. A Primer on FatsA. The Functions of

Fat in the Body Energy source esp.

for muscles Serves as an energy

reserve 1# body fat contains

3500 kcal 30-50# of stored fat

Major component of cell membranesNourishes skin & hair Insulates the body from temperature

extremesCushion the vital organs to protect

them from shock

B. The Functions of Fat in Food

Provide calories (9 per gram)

Provide satietyCarry fat-soluble

vitamins & essential fatty acids

Contribute aroma & flavor

Lipid Terminology

Triglycerides: the major class of dietary lipids, including fats & oils– Made up of 3 units known as fatty

acids and 1 unit called glycerol (backbone)

– Comprise about 95% of lipids in food and the human body

Phospholipids: – 2nd of three main classes of lipids – similar to a triglyceride, but contains

phosphorous

Sterols– 3rd of three main classes of lipids; – Cholesterol

one of the sterols manufactured in the body for a variety of purposes

Fatty acids: – basic units of fat composed of

chains of carbon atoms – an acid group at one end and

hydrogen atoms attached all along their length

II. A Closer View of Fats

A. Chain Length (number of carbons linked together) Shorter = more soluble in water

B. Saturated vs. Unsaturated (number of hydrogens the chain is holding) Maximum = saturated Unsaturated = one or more is missing Point of unsaturation = site where hydrogen is

missing

Saturated fatty acid: a fatty acid carrying the maximum possible number of hydrogen atoms – Animal foods such as

meat, poultry and full-fat dairy products

– Tropical oils such as palm and coconut

Unsaturated fatty acid: a fatty acid with one or more points of unsaturation.– Found in foods from

both plants & animal sources

Monounsaturated fatty acids (one double bond)

Polyunsaturated fatty acids (two or more)

Cont’d

Monounsaturated fatty acid: also called a MUFA; a fatty acid containing one point of unsaturation– Found mostly in

vegetable oils such as olive, canola & peanut

Cont’d Polyunsaturated fatty

acids: also called a PUFA; a fatty acid in which two or more point of unsaturation occur– Found in nuts,

vegetable oils such as safflower, sunflower and soybean, and in fatty fish

B. Essential Fatty Acids

The body can synthesize all of the fatty acids it needs from carbohydrates, fat or protein except for two:

1. Linoleic acid

2. Linolenic acid– PUFAs– Found in plant & fish oils

Omega - 6 versus Omega - 3

Omega – 6 Linoleic

Omega – 3 Linolenic Cold water fish Help dissolve blood clots Lower blood pressure Dilate the arteries

III. Characteristics of Fats in Foods

A. Hydrogenation The process of adding hydrogen to

unsaturated fat to make it more solid and more resistant to chemical changes such as spoiling

Increasing a fat’s saturation can cause a fat to lose its unsaturated health benefits

C. Trans-Fatty Acids

Formed when margarine is processed Hydrogen molecules are on opposite sides of

point of unsaturation “Partially hydrogenated vegetable oil” Link between trans fatty acids and heart

disease Table 4-3, page 107 Keep to minimum

V. Phospholipids

A lipid consisting of a water-soluble head and a fat-soluble tail

Contain phosphorous Component of cell membranes Serve as emulsifiers (allow fats and water to

mix and travel in and out of cells into watery fluid on both sides)

Cont’d Lecithin is a

common phospholipid– Often used as an

emulsifier in foods such as margarine, chocolate & salad dressings

V. Cholesterol – a Sterol Found only in animal products Also made & used in the body:

– Structure of cell membranes– Used to make bile for digestion

Bile: a mixture of compounds, made by the liver, stored in the gallbladder, & secreted into the small intestine

Emulsifies lipids to prepare them for enzymatic digestion & helps transport them into the intestinal wall cells

Cont’d

Used to make the sex hormones estrogen & testosterone

Made into vitamin D with the help of sunlight

Deposited in the artery walls leading to plaque buildup & heart disease

VI. How the Body Handles Fat

A. Digestion

B. Emulsification

C. Absorption

B. Lowering Blood Cholesterol Levels

Eat no more than 30% of calories from fat Eat no more than 8-10% of calories from

saturated fat Eat no more than 10% of calories from

PUFAs MUFAs should make up 10-15% of total

calories Limit daily cholesterol intake to no more

than 300 milligrams

VIII. Fat in the DietA. Food Guide Pyramid

3 groups traditionally account for nine-tenths of the fat in the U.S. diet Fats, oils & sweets group Meat, poultry, fish, dry

beans, eggs & nut group Milk, yogurt & cheese group Most of the fat in our diets

comes from animal products

C. At the Grocery Store

Read labels to determine both the amounts & types of fat contained in foods

D. In the Kitchen Use canola & olive oil for

baking & cooking Prepare lean cuts of meat Bake, broil & steam instead

of frying Use low-fat or fat-free dairy

products & dressings Season with herbs & spices

rather than with fats Incorporate plant-based

protein sources such as soy & legumes

E. At the Table Eat more fresh fruits &

vegetables Use jam instead of butter Limit use of high-fat

condiments including mayo, butter & sour cream or use low-fat varieties

Use mostly monounsaturated vegetable oils such as olive or canola

Eat fewer high-fat desserts

F. Recipe Modification Egg whites Fat-free evaporated

milk Fat-free sour cream Fruit purees Fat-free cream

cheese Oils

IX. Diet & Heart Disease

A. Risk Factors High cholesterol High blood pressure Smoking Diabetes Lack of exercise Stress Obesity Unhealthy diet Age Gender Genetics

Cont’d

B. Ways to Reduce Risk Limit intake of cholesterol

& saturated fat Quit smoking Maintain a healthy weight Eat high fiber foods Increase physical activity Increase fruit & vegetable

consumption Limit alcohol

consumption