Lipids Chapter Health Issues

CHAPTER 4
Lipids

Eleanor D. Schlenker

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

Health Issues and Lipids
 Health concerns related to dietary fat
generally focus on two issues:
1. The high-energy intake associated with a diet high
in fat
2. The negative health effects of saturated and trans
fatty acids

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 2

Health Issues and Lipids – Cont’d
Amount of Fat
 Fat contains 9 kcal/g versus 4 kcal/g (protein

and carbohydrates)
 High-fat intakes may supply excess kcalories,

stored in adipose tissue
 Inappropriate increases in body fat are
associated with type 2 diabetes,
hypertension, and heart disease


Health Issues and Lipids – Cont’d
Type of Fat
 High intakes of saturated fats and cholesterol
promote atherosclerosis, the buildup of fatty deposits
on the interior walls of the major arteries that
increase risk of heart attack or stroke
 Saturated fat is found primarily in animal sources;
cholesterol is found only in animal sources
 Unsaturated fats can decrease risk of cardiovascular
disease
 Trans fats, produced in commercial processing of
lipids, are deleterious to health


Lipids in Nutrition and Health
Food Lipids
 Lipids found in food carry out important body

functions
 Provide fuel for energy
• Food lipids yield 9 kcalories (kcal)/g
 Supply essential fatty acids
• Linoleic acid and alpha-linolenic acid


Lipids in Nutrition and Health –
Cont’d
Food Lipids – cont’d
 Lipids found in food carry out important body

functions – cont’d
 Support absorption of the fat-soluble vitamins
 Add to food palatability
 Promote satiety


Cont’d
Roles in the Body
 Storage source of energy

 Fatty acids are the preferred fuel of the heart
muscle
 Thermal insulation to assist in temperature
regulation
 Protection of vital organs from damage


Cont’d
Roles in the Body – cont’d
 Transmission of nerve impulses

 Form membrane structure

 Carrier of fat-soluble materials

 Lipoproteins
 Fat-soluble vitamins A,D, E, and K
 Precursors of other substances


The Physical and Chemical
Nature of Lipids
Physical Characteristics
 Lipid: Fats, oils, and related compounds that

are insoluble in water and greasy to the touch
 Hidden fat: Foods that may appear to be

mainly carbohydrates (bakery items) or
protein (beef patty) often contain significant
amounts of fat


Nature of Lipids – Cont’d
Chemical Characteristics
 Lipids are organic compounds consisting of a

carbon chain as a “backbone,” with hydrogen
and oxygen atoms and other radicals or
groups of elements attached


Nature of Lipids – Cont’d
Chemical Characteristics – cont’d
 Carbohydrates and lipids have two important

differences:
1. Lipids are more complex in structure, with more
carbon (C) and hydrogen (H) atoms and fewer
oxygen (O) atoms
2. The common structural units of lipids are fatty
acids, whereas the common structural units of
carbohydrates are simple sugars


Characteristics of the Fatty Acids:
Saturation
 Saturated lipids are hard, less saturated are
soft, and unsaturated are liquid at room
temperature
 Fatty acids that have some hydrogen spaces
unfilled are less saturated


Saturation – Cont’d
Saturated Fats
 Food lipids are composed of saturated fatty

acids
 Examples: coconut oil, approximately 88%

saturated; palm kernel oil, approximately 80%
saturated
 Milk fats and meat fats are high in saturated

fatty acids


Monounsaturated
 Food lipids made up of fatty acids with one

hydrogen space unfilled, creating one double
bond
 Examples: canola oil and olive oil


Polyunsaturated
 Fatty acids that have two or more spaces

unfilled with hydrogen, creating two or more
double bonds
 Examples: corn oil and safflower seed oil

 n-3 fatty acids in fatty fish are beneficial for
cardiovascular health
 n-6 fatty acids, e.g., linoleic acid


Characteristics of Fatty Acids:
Chain Length
 Chain length ranges from 4 carbons to 22
carbons
 Chain length affects absorption
 Long-chain fatty acids are more difficult to absorb
and require a helping carrier
 Short- and medium-chain fatty acids are soluble in
water and can be absorbed directly into the
bloodstream
 MCT oil may be used in intestinal diseases


Essential Fatty Acids
 Two essential fatty acids for humans:
1. Linoleic acid (n-6)
2. Alpha-linolenic acid (n-3)

 Arachidonic acid, a fatty acid important in
human nutrition, can be made from linoleic
acid
 Eicosapentaenoic acid and docosahexaenoic
acid can be made from alpha-linolenic acid


Essential Fatty Acids – Cont’d
 Linoleic acid and alpha-linolenic acid have
various roles in the body:
 Skin integrity
 Blood cholesterol regulation
 Growth


Essential Fatty Acids – Cont’d
 Linoleic acid and alpha-linolenic acid have
various roles in the body – cont’d
 Gene expression
 Immune function
 Blood platelet aggregation
 Synthesis of hormone-like agents


Dietary Reference Intakes
 Adequate Intake (AI) for linoleic acid (an n-6
fatty acid):
 17 g/day for men ages 19 to 50 years
 12 g/day for women ages 19 to 50 years
 14 g/day for men age 51 and older
 11 g/day for women age 51 and older


Dietary Reference Intakes –
Cont’d
 AI for alpha-linolenic acid (an n-3 fatty acid):
 1.6 g/day for all adult men
 1.1 g/day for all adult women


Dietary Reference Intakes –
Cont’d
 Special needs of infants
 Arachidonic acid and docosahexaenoic acid play a
critical role in infant development
 Liberal amounts are found in breast milk
 Commercial infant formula is now fortified with
these fatty acids
 Pregnant and lactating women are encouraged to
eat 1-2 portions of fatty sea fish per week


Food Sources

 Best source of linoleic and alpha-linolenic
acids:
 Vegetable oils
 Best sources of linoleic acid:
 Corn oil, safflower oil, soybean oil, cottonseed oil,
sunflower oil, and peanut oil
 Best sources of alpha-linoleic acid:
 Canola oil, soy oil, linseed oil, rapeseed oil, and
dark green leafy vegetables


Food Sources – Cont’d

 Eicosapentaenoic and docosahexaenoic acids
are obtained from fish
 Can be made from alpha-linoleic acid
 Recommend two servings of fish per week
 Vegans or others who do not eat fish may use
fortified foods and fatty-acid-rich algae
 High intakes may lead to excessive bleeding and
interfere with other fatty acid metabolism
 Foods are always the best sources


Triglycerides
 Fatty acids are stored in the body in the form
of triglycerides


Triglycerides – Cont’d
 Triglycerides are made of three fatty acids
attached to a glycerol base
 Glycerides contain glycerol and fatty acids
• Monoglyceride: glycerol is combined with one fatty acid
• Diglyceride: with two fatty acids
• Triglyceride: with three fatty acids


Degree of Saturation
 Food lipids contain both saturated and
unsaturated fats
 Foods from animal sources—such as meat,
milk, and eggs—contain more saturated fats


Degree of Saturation – Cont’d
 Most food lipids from plant sources, primarily
vegetable oils, are unsaturated but there are
exceptions:
 Coconut oil and palm kernel oil are among the
most saturated fats occurring naturally in foods


Degree of Saturation – Cont’d
 The nutrition label can guide a consumer's
choice of fats
 Indicates the number of grams of total fat,
saturated fat, unsaturated fat, and trans fat per
serving
 Importance of considering serving sizes
 Foods free of trans fats are not necessarily healthy


Cis Versus Trans Fats
 Hydrogenation changes unsaturated liquid
oils into solid fats such as margarine and
shortening


Cis Versus Trans Fats – Cont’d
 When oils are partially hydrogenated to
produce more solid fats, the normal bend can
change such that the two structural parts are
on opposite sides of the bend
 This form is called a trans fatty acid, meaning
“opposite side”


Cis Versus Trans Fats – Cont’d
 Trans fatty acids are found in breads, cakes,
cookies, crackers, margarine, and frozen
potato products
 Trans fatty acids decrease high-density
lipoprotein (HDL) cholesterol levels and
increase low-density lipoprotein (LDL)
cholesterol levels


Visible and Hidden Fat
 Visible Fat
 Butter, margarine, vegetable oil, salad dressing,
bacon, etc.
 Hidden Fat
 Milk (except nonfat), egg yolk, cheese, nuts,
seeds, olives, bakery items, frozen entrees
 Meat and poultry contain visible and hidden fat


Appropriate Intakes of Fat and
Carbohydrates
 Acceptable Macronutrient Distribution Range
(AMDR) for fat:
 20% to 35% of total kcalories
 Keep saturated fat less than 10% of total
calories


Appropriate Intakes of Fat and
Carbohydrates – Cont’d
 AMDR for carbohydrates:
 45% to 65% of total kcalories
 Low carbohydrate diets may contain >45% of
kcalories as fat
 Fat intakes below 10% of energy intake may
not supply sufficient essential fatty acids


Health Promotion
 Fast-food restaurants add to fat intake
 On days with a fast-food meal, men and women
obtain 34.9% and 34.6%, respectively, of their
total kcalories from fat
 On days when all meals are eaten at home or at
food outlets other than the fast-food variety, fat
supplies only 33.6% and 32.7% of total kcalories
in men and women, respectively.


Health Promotion – Cont’d
Lowering Fat Intake
 Substituting a modified-fat food for a higher-

fat food
 Limiting portion sizes of higher-fat foods to

reduce both fat and kcalories
 Choosing a food preparation method that
limits or eliminates fat


Fat Replacers
 Food technologists have developed fat
replacers for use in processed foods
 In the United States, 79% of consumers buy
foods containing fat replacers


Fat Replacers – Cont’d
 Ingredients that can fulfill the functional role
of fats in recipes but are lower in kcalories
than fat
 Most are carbohydrates—plant
polysaccharides, celluloses, or gums
 Most act as thickeners and emulsifiers


Fat Replacers – Cont’d
 Olestra interferes with absorption of fat-
soluble vitamins, so these are added to
olestra-containing products
 Certain fat replacers are not digested and
remain in the stomach longer; they may add
to satiety and assist in appetite control
 Most (but not all) add fewer kcalories than
would fat


Lipid-Related Compounds
Cholesterol
 Belongs to a family of substances called

steroids and travels in the blood attached to
long-chain fatty acids (as cholesterol esters)


Lipid-Related Compounds –
Cont’d
Cholesterol – cont’d
 Functions

 Required for normal body function and can be
synthesized in the liver
 Precursor to steroid hormones
 Formation of bile acids
 Component of brain and nerve tissue
 Component of cell membranes


Cholesterol
 Cholesterol occurs naturally in animal foods
but not plant foods
 Food sources containing cholesterol:
 Egg yolk, meat, whole milk, and cheese
 Liver and organ meats
 Animal fats (but not plant fats)


Cholesterol – Cont’d
Suggested Cholesterol Intake
 The American Heart Association

recommends that dietary cholesterol be held
to 300 mg/day or less
 Intake averages about 358 mg in men and

237 mg in women
 Certain plant sterols interfere with absorption


Lipoproteins
Function
 The liver serves as the body's clearing house

for fatty acids and cholesterol whether
obtained from the diet or produced or
released from body tissues


Lipoproteins – Cont’d
Function – cont’d
 When received by the liver, fatty acids and

cholesterol are:
 Packaged into lipoproteins
 Released into the circulation for transport to cells


Lipid Transport
 Lipids are insoluble in water and therefore
insoluble in water-based blood
 The body produces lipoproteins, packages of
lipids wrapped in water-soluble protein


Lipid Transport – Cont’d
 Phospholipids are molecules in which one of
the three fatty acids attached to a glycerol
base is replaced with a water-soluble
phosphate (PO4-3) group


Lipid Transport – Cont’d
 Phospholipids in cell membranes help lipid
molecules move from the circulatory system
into the cell
 The lipoproteins with their attached
apolipoprotein serve as the major vehicle for
lipid transport in the blood


Classes of Lipoproteins
 Lipoproteins are classified according to their
density
 Five lipoprotein classes are:
 Chylomicrons
 Very low-density lipoproteins (VLDLs)
 Intermediate density lipoproteins (IDLs)
 Low-density lipoproteins (LDLs)
 High-density lipoproteins (HDLs)


Cholesterol, Lipoproteins, and
Cardiovascular Risk
 LDLs
 Transport cholesterol from the liver to the tissues
 Elevated LDLs promote atherosclerosis
 Cause buildup of fatty plaque in blood vessels

 HDLs
 Return cholesterol from the cells to the liver for
excretion
 Slow or prevent the progression of atherosclerosis
and lower cardiovascular risk


Digestion-Absorption-Metabolism
Digestion
 Triglycerides are broken down into individual

fatty acids for absorption
Mouth
 No chemical breakdown of lipids


– Cont’d
Stomach
 Gastric lipase (tributyrinase) acts on

emulsified butterfat
 General peristalsis continues the mechanical

mixing of lipids with the stomach contents


– Cont’d
Small Intestine
 Digestive secretions for lipid breakdown

come from three sources:
1. Bile from the liver and gallbladder: cholecystokinin
(CCK) triggers its release
2. Enzymes from the pancreas: pancreatic lipase
and cholesterol esterase
3. Enzyme from the small intestine: lecithinase


Absorption
 Lipid absorption is complicated
 Transporting lipids from the small intestine into the
bloodstream takes place in three stages:
• Stage I: Initial lipid absorption (micellar bile-lipid
complex)
• Stage II: Absorption within the intestinal wall (enteric
lipase digestion and triglyceride synthesis)
• Stage III: Final absorption and transport (chylomicrons
and lipoprotein lipase) via the portal blood


Lipids Chapter Health Issues

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Lipids Chapter Health Issues

Similar to Lipids Chapter Health Issues (20)

Recently uploaded

Recently uploaded (20)

Lipids Chapter Health Issues