The document discusses the properties and functions of dietary fats and lipids. It explains that fats provide energy density and are stored in adipose tissue. Dietary fats include saturated, monounsaturated, and polyunsaturated fatty acids. Lipids include triglycerides, phospholipids, and sterols like cholesterol. Lipids play structural and functional roles in cells and as carriers of fat-soluble vitamins and minerals. Omega-3 and omega-6 fatty acids are essential but must be obtained through diet.

1. Presented By
Mokoena N.W
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2.  Fats are a concentrated fuel source for the human
energy system.
 A large amount of energy can be stored in a
relatively small space within adipose tissue as
compared with carbohydrates that are stored as
glycogen.
 As such, fats supplement carbohydrates (the
primary fuel) as an additional energy source.
 In food, fats occur in the form of either solid fat or
liquid oil.
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3.  Fats and lipids constitute approximately 34% of the
energy in the human diet.
 Because it is rich in energy and provides 9kcal/g of
energy, humans are able to obtain adequate energy
with a reasonable daily consumption of fat-
containing foods.
 Dietary fat is stored in adipose (fat) cells located in
depots on the human frame.
 The ability to store and use large amounts of fat
enables humans to survive without food for weeks
and sometimes months.
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4.  Unlike carbohydrates, lipids are not polymers; they
are small molecules extracted from animal and
plant tissues.
 They constitute a heterogeneous group of
compounds which are related more by their
physical structure than by their chemical
properties.
 They are insoluble in water and soluble in alcohol,
ether, benzene, chloroform and acetone.
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5.  The overall name of the chemical group of fats and
fat-related compounds is lipids, which comes from
the Greek word lipos, meaning “fat”.
 The word lipid appears in combination words that
are used for fat-related health conditions. For
example, an elevated level of fat in the blood is
called hyperlipidaemia.
 All lipids are composed of the same basic chemical
elements as carbohydrates: carbon, hydrogen and
oxygen.
 The majority of dietary fats are glycerides, which
are composed of fatty acids attached to glycerol.
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6.  Structural fat pads hold the body organs and nerves in
position and protect them from against traumatic
injury and shock.
 Fat pads on the palms and buttocks protect the bones
from mechanical pressure.
 Humans also have a subcutaneous layer of fat that
insulates the body, preserving body heat and
maintaining body temperature.
 Dietary fat is also essential for the digestion,
absorption, and transport of the fat-soluble vitamins
and phytochemicals such as carotenoids and lycopene.
 Dietary fat depresses gastric secretions, slows gastric
emptying, and stimulates biliary and pancreatic flow
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7.  In food, fat provides flavour, aroma and texture
(Smooth and tender).
 It also increases palatability and satiety but it has
several functions in the body.
 Fat provides energy.
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8.  Fatty acids, which are the building blocks of
triglycerides, can be classified by their length as short-
, medium-, or long-chain fatty acids.
 The chains contain carbon atoms with a methyl group
(CH3) on one end (also known as the omega end) and
an acid carboxyl group (COOH) on the other end.
 Short-chain fatty acids have 2 to 4 carbons, medium-
chain fatty acids have 6 to 10 carbons, and long-chain
fatty acids have more than 12 carbons.
 Fatty acids can be classified according to their
saturation or essentiality, both of which are significant
characteristics.
 Are rarely free in nature and almost always are linked
to other molecules by their hydrophilic carboxylic acid
head group
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9.  When a substance is described as saturated, it
contains all of the material that it is capable of
holding. For example, a sponge is saturated with
water when it holds all of the water that it can
contain.
 Similarly, fatty acids are saturated or unsaturated
according to whether each carbon is filled with
hydrogen.
 Thus, a saturated fatty acid is heavy and dense
(solid at room temperature).
 If most of the fatty acids in a triglyceride are
saturated, that fat is said to be a saturated fat.
 Most saturated fats are of animal origin.
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10.  Saturated fats, especially those with long chains,
are solid at room temperature; but a fat such as
coconut oil, which is also highly saturated, is
semiliquid at room temperature because the
predominant fatty acids are short.
 They are usually from animal sources like meat,
milk, cheese, butter, egg yolk, cream.
 There are some plants that contain saturated fats
like coconut, palm and cocoa.
 Eating a large amount of saturated fats can raise
blood cholesterol.
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11. Animal Sources
 Certain cuts of beef
and pork
 Chicken and turkey
skin
 Full cream dairy
products
 Butter
 Lard
Plant Sources
 Coconut oil
 Cocoa butter
 Chocolate
 Palm oil
 Hydrogenated fats
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12.  A fatty acid that is not completely filled with all of the
hydrogen that it can hold is unsaturated; as a result, it is
less heavy and less dense (i.e. liquid at room temperature).
 If most of the fatty acids in a triglyceride are unsaturated,
that fat is said to be an unsaturated fat.
 If the fatty acids have one unfilled spot (i.e. one double
bond between carbon atoms), the fat is called
monounsaturated fat. Examples, olive, canola, peanut, nuts
(macadamia, hazelnuts, almonds, and pecans), avocados.
 If the fatty acids have two or more unfilled spots (i.e. more
than one double bond between the carbon atoms), the fat is
called polyunsaturated fat. Examples, safflower, sunflower,
corn and soybean oils,
 Because fatty acids with double bonds are vulnerable to
oxidative damage, humans and other warm-blooded
organisms store fat predominantly as saturated palmitic
fatty acid (C16:0) and stearic fatty acid (C18:0)
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13.  Unsaturated fats can either be monounsaturated or
polyunsaturated.
 They are generally liquid at room temperature.
 They can reduce blood cholesterol when they
replace saturated fats in the diet. They lower the
LDL but not the HDL cholesterol.

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14. Monounsaturated
Fats
 Canola oil
 Olive oil
 Peanut butter
 Pecans & almonds
 Avocado
Polyunsaturated Fats
 Sunflower oil
 Safflower oil
 Corn oil
 Soybean oil
 Fishes & their
products
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15.  Fatty acids are also characterized by the location of
their double bonds.
 In Omega notation a lower case omega (ω) or n is used
to refer to the placement of the first double bond
counting from the methyl end.
 Thus arachidonic acid (20:4 ω-6 or 20:4 n-6), the
major highly polyunsaturated fat in membranes of land
animals, is an omega-6 fatty acid.
 It has twenty carbons and four double bonds, the first
of which is six carbons away from the terminal methyl
group.
 Eicosapentaenoic acid (EPA) (20:5 ω-3 or 20:5 n-3) is
found in marine organisms and is an omega-3 fatty
acid.
 It has five double bonds, the first of which is three
carbons from the terminal methyl group.
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16.  Fats occur in foods and in most animals in the
form of triglycerides. If it is solid at room
temperature it is called fat and if it is liquid it is
called oil.
 Triglycerides are formed by joining three FA to a
glycerol side chain to avoid tissue damage.
 OH group on each FA is bound to an OH group on
the glycerol
 H2O molecule is released at each side and an ester
linkage is formed
 FA linked to glycerol are neutral and triglycerides
are H2O insoluble.
 Neutral fats can be safely transported in the blood
and stored in the fat cell as an energy reserve.
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17.  Different fatty acids can comprise a single
triglyceride and are dependent on the dietary fatty
acids and the amount of synthesis taking place.
 FAs that make up the triglyceride in the food
source reflect the needs of plant or animals, e.g:
Animals store fat in the form of SFA not
susceptible to oxidative damage during storage.
 Fish store fat in the form of unsaturated FA (liquid)
because high no of double bound lowers the
temperature at which the fat is liquid and available
for metabolic functions.
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18.  Phospholipids are derivatives of phosphatidic acid,
a triglyceride modified to contain a phosphate
group at the third position.
 Membrane phospholipids usually contain one SFA
(C16 to C18) at C-1 and a highly PUFA (C16 to
C20) at C-2, usually one of the essential fatty acids
 Because it is polar at physiologic pH, the
phosphate-containing portion of the molecule
forms hydrogen bonds with water, whereas the two
fatty acids have hydrophobic interactions with
other fatty acids.
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19.  Phospholipids are called biologic amphiphiles.
 The hydrophilic head & hydrophobic tail form an
emulsification between H2O and oil and act as a
detergent to dissolve the fat into the H2O.
 Phospholipids provide a lipid barrier to unregulated
transport of H2O soluble molecules into the cell.
 Lecithin (Phosphatidylcoline) and its derivative,
sphingomyelin are the two major phospholipids in the
biomembrane.
 They are essential to biomembrane structure and
function. Lecithin is a major component of the HDL,
which is used to remove cholesterol from the cell
membrane.
 Lecithin is widely distributed in the food supply i.e.
liver, egg yolk, soybean, peanuts, legumes, spinach &
wheat germ.
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20.  Steroids are lipids derived from a four membrane saturated
ring e.g. glucocorticoids (Cortisone), mineralcorticoids
(aldosterone), (estradiol) and bile acids.
 Cholesterol is a sterol, waxy fat like substance found in cell
membranes of all animals. It is found in all foods of animal
origin even though we cannot see it or taste it. Plants do not
contain cholesterol.
 The body uses cholesterol to make hormones like estrogen,
progesterone and testosterone. It is also needed to make
cell walls, bile and vitamin D.
 Even though cholesterol is needed in the body, it is not an
essential nutrient because the liver can make all the
cholesterol the body needs.
 When there is too much cholesterol in the blood, it builds
up in the arteries and thus increases the risk for heart
diseases. It is therefore important to limit the intake of
dietary cholesterol. 20

21.  Lipoproteins, which are the major vehicles for lipid transport in
the bloodstream, are combinations of triglycerides, protein,
phospholipids, cholesterol, and other fat-soluble substances.
 Because fat is insoluble in water and because blood is
predominantly water, fat cannot freely travel in the bloodstream;
it needs a water soluble carrier.
 The body solves the problem by wrapping small particles of fat in
a covering of protein, which is hydrophilic.
 The blood then transports these packages of fat to and from the
cells throughout the body to supply needed nutrients.
 A lipoprotein’s relative load of fat and protein determines its
density.
 The higher the protein load, the higher the lipoprotein’s density.
The lower the protein load, the lower the lipoprotein’s density.
 Low-density lipoproteins carry fat and cholesterol to cells. High-
density lipoproteins carry free cholesterol from body tissues back
to the liver for metabolism.
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22.  Commercially synthesized lipids for specific
purposes e.g. MCT, structured lipids and fat
substitutes/replacers.
 MCT- they are rapidly hydrolysed in the GIT and
they can be directly absorbed into the blood. They
are used for patients in catabolic states (e.g.
cancer, AIDS) and with malabsorption problems.
 Structured lipids- MCT that are combined with a
desired FA to increase the absorption rate of the
LCT.
 Fat substitutes or fat replacers-compounds that
are structurally different from fats however they
are similar to fat in texture, viscosity and mouth
feel. They are not metabolized and absorbed in the
gut. They are often used for reducing fat intake. 22

23.  Olestra is an example of synthetic fat/lipid. Fat
substitutes have become more common as
manufacturers target people who through
misinformation have acquired aversions to fats or
who would like to diet without reducing food
intake.
 The olestra molecule is too large to be metabolized
and passes through the body unchanged, but
because it acts as a lipid, it can cause depletion of
fat-soluble vitamins.
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24.  The three types of omega-3 fatty acids involved in
human physiology are α-linolenic acid (ALA) (found in
plant oils), eicosapentaenoic acid (EPA),
and docosahexaenoic acid (DHA) (both commonly
found in marine oils).
 Marine algae and phytoplankton are primary sources of
omega-3 fatty acids.
 Common sources of plant oils containing the omega-3
ALA fatty acid include walnut, edible seeds, and
flaxseed oil, while sources of animal omega-3 EPA and
DHA fatty acids include fish oils, egg oil, squid oils,
and krill oil.
 Dietary supplementation with omega-3 fatty acids does
not appear to affect the risk of death, cancer or heart
disease
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25.  Omega-3 fatty acids are important for
normal metabolism.
 Mammals are unable to synthesize omega-3 fatty
acids, but can obtain the shorter-chain omega-3
fatty acid ALA (18 carbons and 3 double bonds)
through diet and use it to form the more important
long-chain omega-3 fatty acids, EPA (20 carbons
and 5 double bonds) and then from EPA, the most
crucial, DHA (22 carbons and 6 double bonds).[
 The ability to make the longer-chain omega-3
fatty acids from ALA may be impaired in aging.
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26.  Omega-6 fatty acids (also referred to as ω-6 fatty
acids or n-6 fatty acids) are a family of pro-
inflammatory and anti-inflammatory polyunsaturated
fatty acids that have in common a final carbon-
carbon double bond in the n-6 position, that is, the
sixth bond, counting from the methyl end.
 The biological effects of the omega-6 fatty acids are
largely produced during & after physical activity for the
purpose of promoting growth and during the
inflammatory cascade to halt cell damage and promote
cell repair by their conversion to omega-
6 eicosanoids that bind to diverse receptors found in
every tissue of the body.
 Linoleic fatty acid is the most common omega 6 fatty
acid
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27. Food sources of omega 6 fatty acids
 Rapeseed oil
 Soybean
 Sunflower
 Poultry
 Eggs
 Avocados
 Nuts
 Safflower
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28.  Sources of ω -3- fatty acids are salmon, sardines,
pilchards, crab, shrimps, oysters + mackerel.
 Commercially some eggs and milk are supplemented
with ω -3FA.
 The optimal ratio for ω -6 / ω -3 is 2:1 to 3:1. Excess
ω -6 in the diet saturates the enzymes and prevents
conversion of ALA into EPA & DHA
 Food sources of linoleic fatty acids are sunflower,
safflower oils.
 Functions of ω- 3 Fatty acid
 Development of the brain and the retina
 Improves the immune system
 Can protect against hypertension, heart diseases, etc.
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29. EFA deficiency
 The brain, CNS and membranes throughout the
body require EPA + DHA for optimal function.
 Deficiency increases the risk of developing learning
problems, poor vision and polydipsia (frequent
drinking due to thirst).
 Abnormal ω- 6/ ω- 3 ratios is linked to incidence
of heart diseases, arthritis, cancer, etc.
 Deficiencies of ω – 6 may lead to growth failure,
fatty liver and skin lesions.
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30.  Occur as a result of hydrogenation of
unsaturated fatty acids
 Sources: hydrogenated margarine
 Baked products
 Salty snacks
 Increased intake is associated with:
 Coronary heart diseases
 Cancers
 Inhibition of the conversion of ALA into EPA and
DHA.
 Cis configuration Trans -configuration
 Butter and animal fat may contain trans-fatty
acids from bacteria fermentation.
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31.  THANK YOU
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