Download Chapter Four The Lipids: Fats & Oils

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 Fats
A.
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 membranes
 Nourishes skin & hair
 Insulates the body from temperature
extremes
 Cushion the vital organs to protect
them from shock

B. The Functions of Fat in Food
Provide calories (9 per
gram)
 Provide satiety
 Carry 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)

B.
Shorter = more soluble in water
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 fullfat 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

VI. How the Body Handles Fat
A.
B.
C.
Digestion
Emulsification
Absorption
VII. Lipids & Health
A.
B.
C.
D.
Good vs. Bad Cholesterol
http://www.americanheart.org/
http://www.mayohealth.org/
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 Diet
A.
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)
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