Transcript Chapter One

C HAPTER
5
Fats: Essential
Energy-Supplying
Nutrients
PowerPoint® Lecture Slides prepared by
James Bailey, University of Tennessee
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings.
What Are Lipids?
Lipids: diverse class of molecules that are insoluble
in water.
 Lipids (fats) do not dissolve in water
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Three types of lipids are found in foods
 Triglycerides (the fats and oils)
 Phospholipids (lecithin)
 Sterols (cholesterol)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Triglycerides (the fats and oils)
Triglycerides are composed of
 One glycerol molecule
 Glycerol: a 3-carbon alcohol that is the backbone of a
triglyceride
 Three fatty acid molecules
 Fatty acids: long chains of carbon atoms surrounded
by hydrogen atoms
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Triglycerides
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.1
Triglycerides contain three fatty acids.
Fatty acids can differ in:
 Length of their carbon chain
 Short- (<6), medium- (6–12), or long- (>13) chain
 Level of saturation
 Saturation refers to how many hydrogen atoms
surround each carbon
 Shape (straight, slightly bent or very bent)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Triglycerides
Saturated fatty acids have hydrogen atoms surrounding every
carbon in the chain. No double bonds.
Monounsaturated fatty acids lack hydrogen atoms in one
region. One double bond.
Polyunsaturated fatty acids lack hydrogen atoms in multiple
locations. Two or more double bonds.
Note: Each double bond causes the loss of two hydrogen
atoms. The molecule can bend or flex at the point where the
double bond is. So, typically, the more double bonds, the
more bent the molecule.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Saturated Fatty Acids are Rigid (straight)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.3a–b
Monounsaturated fatty acids have one double
bond (and typically (cis) have one bend.)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.3c–d
The shape of a triglyceride is determined by the
saturation of the three fatty acids it contains.
Saturated fatty acids can pack more tightly (stable)
together and are solid at room temperature.
 For example, coconut oil, animal fats, and butter,
and rich sources of saturated fatty acids
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Unsaturates are more bent
Unsaturated fatty acids are more bent and do not
stack together well; they will be liquid at room
temperature.
 Unsaturated fatty acids are the predominant type in
plants from temperate climates;
 Plants grown in equatorial places are more likely to
produce saturates. Examples include: coconut and
palm kernel oil
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The arrangement of hydrogen atoms about the
double bond (point of unsaturation)
determines if there are bends.
The hydrogen atoms at the unsaturated part of the
molecule can be arranged in different positions.
 Cis: same side of the carbon chain (these bend); in
nature most, but not all fatty acids are cis.
 Trans: opposite sides of the chain (these remain
straight)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The cis arrangement has both hydrogens on
the same side of the molecule.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.5
There is a food processing technique called
hydrogenation that companies use to make
oils into solid fats (we call them shortening in the U.S.)
Hydrogenation: the addition of hydrogen atoms to
unsaturated fatty acids.
 Converts liquid fats (oils) into a semi-solid (spreadable) or
solid form
 Used to create margarine from plant oil
 Partial hydrogenation may create trans fatty acids
 On the food label, look for the term partially hydrogenated
oil
 You may also see fully hydrogenated oil, in which case
there is no trans fatty acid. But, to be honest, this process is
hard on the oil and harms the quality of the product.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Research on Lipids and Health
 trans fats from processed foods are harmful to
health; they lower “good” cholesterol and raise
“bad” cholesterol levels;
 Trans fats from natural foods, such as cow milk
from animals that eat green (not grains) are healthpromoting;
 Saturated fats can be healthful in the diet. They
should be from minimally processed, natural foods
such as butter, coconut and palm.
 In the U.S., as of January 2006 trans fat content is
required on the food label.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fatty Acids and Health
Essential fatty acids
 There are two fatty acids cannot be synthesized in
the body. They are essential and must be obtained
in the diet.
 They are:
 Linoleic acid (an omega 6 shape)
 Alpha linolenic acid (an omega 3 shape)
They are converted into important regulatory
compounds in the body.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Omega-6 Essential LA
Linoleic acid (omega-6 fatty acid)
 Found in vegetable and nut oils – such as corn and
soy oil
 Can be converted by the body to arachidonic acid
which is involved in blood clotting and blood
pressure
 You can eat arachadonic acid, already formed, from
animal milk, muscle and organ meats.
 Arachadonic Acid (AA) will form important
regulator molecules.
 These are more pro-inflammatory.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Omega-3 Essential: ALA
Alpha-linoleic acid (ALA)
(omega-3 fatty acid)
 Found in vegetables oils such as: chia, perilla, flax,
lingonberry and purslane.
 ALA is converted to EPA and DHA in our bodies –
These contribute to the formation of important
regulators of inflammation, blood clotting and
blood pressure. These are more anti-inflammatory.
 You can get EPA and DHA, already formed, in
shellfish and fish.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Phospholipids
Phospholipids
 Are composed of
 Glycerol backbone
 Two fatty acids
 Phosphate plus another group
 Have a very unusual character: one part of the
molecule is soluble in water; another part is soluble
in lipid
 They are vital to build cell membranes
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Phospholipids arrange themselves to put the fat-liking fatty acid legs
(light brown) together and the phosphate head (blue color) at the
outside. See how this builds a very effective membrane to surround
each cell.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.7
Sterols
Sterols: lipids containing multiple rings of carbon
atoms.
 Are essential components of cell membranes and
many hormones
 Cholesterol is the major sterol found in the body
 Our liver makes quite a bit of cholesterol each day,
to serve many purposes.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Sterols: The basic sterol ring structure is
shown at left; the cholesterol molecule is on
the right.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.8
The Role of Fat
Energy
 Fat is very energy dense, containing 9 kcal/gram or
 Much of the energy used during rest comes from fat
 Fat is used for energy during exercise, especially
after glycogen is depleted
 Fat is also used for energy storage
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Role of Fat
Fat-soluble vitamins
 Vitamins A, D, E, and K are soluble in fat; fat is
required for their transport
Fat is essential to many body functions




Cell membrane structure
Nerve cell transmissions
Protection of internal organs
Insulation to retain body heat
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Role of Fats
Fat provides flavor and texture to foods.
Fat contributes to making us feel satiated because
 Fats are more energy dense than carbohydrates or
protein
 Fats take longer to digest
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Digestion of Fats
Fats are not digested and absorbed easily because
they are insoluble in water.
 No digestion of fats occurs in the watery
environments of the mouth
 Minimal digestion occurs in the stomach from
gastric lipase
Digestion and absorption of fats occurs primarily in
the small intestine.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Digestion of Fats
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.10
Digestion of Fats
As fat enters the small intestine
 Bile is secreted from the gall bladder into the small
intestine
 Bile is produced by the liver and stored in the gall
bladder
 Bile disperses fat into smaller fat droplets
 Pancreatic enzymes break triglycerides into two
separate fatty acids and a monoglyceride
 Fat enters the mucosal cell as a micelle (fatty acids,
monoglycerides, phospholipids, and sterols)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Digestion of Fats
In the intestinal mucosal cell
 Fatty acids are reattached to the monoglyceride to
reform triglycerides
 A small amount of protein is added to the lipids
forming a chylomicron
 Chylomicron: a lipoprotein produced by cells
lining the small intestine
 Composed of triglycerides surrounded by
phospholipids and proteins
 Soluble in water
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Structure of a Lipoprotein – a sphere of fatty compounds (cholesterol
and fatty acids) surrounded by a single layer of phospholipids and a
few proteins (shown in purple).
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.11
Digestion of Fats
Chylomicrons are the transport vehicle that removes
absorbed fats from the small intestine.
 Travel through the lymphatic system
 Are transferred to the bloodstream
Just a note for you: short- and medium-chain fatty
acids are absorbed more quickly since they are not
arranged into chylomicrons.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Digestion of Fats
 Once the chylomicron gets to a cell in the body, the
triglycerides in the chylomicrons must be
disassembled by lipoprotein lipase into two fatty acids
and a monoglyceride before they can pass through the
cell membrane
 After entering the cell, the two fatty acids and
monoglyceride reform a triglyceride
 The triglyceride can be
 Used immediately for energy
 Used to make lipid-containing compounds
 Stored in liver and muscle cells
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Lipoproteins Vary in Composition and Function.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.17 (1 of 2)
Healthy people carry more of their lipids as HDL than as LDL.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.17 (2 of 2)
How Much Fat in Our Diet?
The Acceptable Macronutrient Distribution Range
(AMDR) for fat:
20–35% of calories should be from fat
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
How Much Fat?
The type of fat consumed is important.
 Saturated fat should be no more than 7% of total
calories
 Trans fatty acids should be reduced to the absolute
minimum
 Most fat in our diets should be from
monounsaturated fats (e.g., olive oil).
 The book wants you to have a lot of
polyunsaturated oils, but that puts you at risk for
quite a few health challenges. Please ask in class
when I’m on site.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Beneficial Fats
Increased consumption of “good” fats is advised
 Increase consumption of omega-3 fatty acids
 Flaxseed oil, fish, walnuts
Avoid consumption of contaminated fish
 Mercury, PCB’s levels can be high some fish–
especially top of the food chain predators (tuna,
shark)
 Eat small fish like anchovies, sardines, herring and
such. They have good fats and no bad chemicals.

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Health Problems from Fat
Cardiovascular disease
 Dysfunction of the heart or blood vessels
 Can result in heart attack or stroke
The type of fat in our diet can contribute to or help
protect against cardiovascular disease.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiovascular Disease
Risk factors for cardiovascular disease include






Being overweight
Physical inactivity
Smoking
High blood pressure
Diabetes
High blood cholesterol
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Transport Lipids: Like a shuttle bus…
There are four types of lipid transport molecules in
the blood. They are:
 Chylomicrons (dietary lipids)
 VLDLs—very low-density lipoproteins
 LDLs—low-density lipoproteins
 “bad cholesterol”
 HDLs—high-density lipoproteins
 “good cholesterol”
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiovascular Disease
The text states that diets high in saturated fats
 Decrease the removal of LDLs from the blood
 Contribute to the formation of plaques that can
block arteries
 Increase triglyceride levels (chylomicrons and
VLDLs)
 BUT, I need you to know that plaques formed with
saturates are very stable and do not break off and
cause disruptions of blood flow (as those with
polyunsaturates will). I think you need to eat some
saturates in your diet. They are stable against
oxidation and stable in plaque.
(sara)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiovascular Disease
Cross-section of (a) normal artery and (b) a partially blocked
artery. It’s important to note that the blockage (plaque) is inside
the wall of the artery and it crowds the area where blood needs to
flow.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 5.16
Cardiovascular Disease
Trans fatty acids
 Can raise blood cholesterol levels more than
saturated fat
 Are abundant in hydrogenated vegetable oils
(margarine, vegetable oil spreads)
 Should be reduced to the absolute minimum
 Some communities in the U.S. have banned the use
of trans fats in restaurant foods.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiovascular Disease
How can certain fats protect against heart disease?
Diets high in omega-3 fatty acids (along with
moderate exercise) can increase HDL “good”
cholesterol levels.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings