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Chapter Four
The Lipids: Fats & Oils
NUT SCI 242 Food & Nutritional Health
© Karen Lacey, MS ,RD, CD
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
Cont’d
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
Cont’d
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
Cont’d
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
Cont’d 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
Cont’d 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. Liquid vs Solid More saturated a fat is, the
more solid it is at room temperature
More unsaturated a fat is, the more liquid it is at room temperature
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
VII. Lipids & Health
A. Good vs. Bad Cholesterol
B. http://www.americanheart.org/
C. http://www.mayohealth.org/
D. http://www.fda.gov/
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
B. Fat Substitutes
Carbohydrate-based– Help retain moisture to maintain the juiciness or
creaminess that is lost with fat reduction– Carrageenan, fruit purees, gelatin, gums,
starches & products made from fiber Protein-based
– Proteins are cooked & blended to form tiny round particles that trap water to maintain the mouth feel of fat
– Whey protein concentrate (Dairy-Lo), or milk & egg white protein (Simplesse)
Cont’d
Fat-based– Are either only partially digestible or
completely undigestible to prevent absorption of fat
– Caprenin (substitute for cocoa butter in candy), Salatrim (found in low fat baking chips), and olestra (often found in fat free potato chips)
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