Lipids/Fats
By Jennifer Turley and Joan Thompson
© 2016 Cengage
Overview
Categories, Chemistry, Functions & Foods of:
• Fats/Lipids
• Triglycerides
– Fatty Acids
• Phospholipids
• Sterols
Lipids - Fats
Composition: Fats contain Carbon,
Hydrogen, Oxygen
• Lipids are organic compounds
• Lipids are soluble in fat
Categories of Lipids:
1. Triglycerides
2. Phospholipids
3. Sterols
Triglycerides “Fats”,
Part 1
• Energy Yield: Fats provide 9
Calories/gram.
– Fats are the only type of lipid that
the body can convert to ATP or
produce energy from.
– Fats are the most Calorically Dense
energy-producing nutrient.
Triglycerides “Fats”,
Part 2
• Caloric density: Refers to the
Calories yielded per weight of the
substance.
– Triglycerides (dietary fats) provide 9
Calories per gram while proteins and
digestible carbohydrates provide 4
Calories per gram and alcohol provides
7 Calories per gram.
Triglyceride Model
Actual Triglyceride
Categories of Fatty Acids
Dietary fats are defined by the composition of the
fatty acids in the triglyceride.
1. Saturated fat food sources are comprised of
mostly saturated fatty acids (SFAs).
2. Monounsaturated fat food sources are
comprised mostly of monounsaturated fatty acids
(MUFAs).
3. Polyunsaturated fat food sources are comprised
mostly of polyunsaturated fatty acids (PUFAs).
Examples of Fatty Acids
Saturated Fatty Acids
(SFA)
• Have 0 double bonds between the carbons.
• Are found in animal products, hydrogenated
vegetable fats, & tropical oils (palm &
coconut oils).
• Are solid at room temperature & unhealthy
when consumed in excess.
Monounsaturated
fatty acids (MUFA)
• Have 1 double bond
in the carbon chain
• Are healthy
• High levels are in olive oil, canola oil, almonds, & avocado
• Become semisolid when refrigerated
• Are liquid at room temperature
Polyunsaturated fatty acids (PUFA)
• Have >1 double bond in the carbon chain.
• Some are essential for the body.
• Are found in plant oils like corn,
cottonseed, safflower, and sunflower oil.
• Are liquid at room temperature.
• Too much can promote cancer.
Fat Food Sources
• Oils, butter, cream, lard, margarine,
dressings, cream cheese, olives,
nuts & seeds are all examples of
foods high in dietary fat.
• Try to chose healthy fats from plant
sources, like those shown on the
right.
Fatty Acid Composition of Common Fats
Essential Fatty Acids,
Part 1
• The body cannot make the essential
fatty acids (EFAs).
• Linoleic Acid & Alpha-Linolenic Acid.
• These EFAs are found in plant oils &
plant foods.
• Deficiency characteristics develop
when they are lacking in the diet.
Essential Fatty Acids,
Part 2
• The AMDR level for adults that will optimize
health are:
– 5-10% of Calories from Linoleic Acid
– 0.6-1.2% of Calories from Alpha-Linolenic Acid
• Linoleic Acid is an omega 6 fatty acid.
• Alpha-Linolenic Acid is an omega 3 fatty acid.
Essential Fatty Acids,
Part 3
Created in food
processing when
PUFAs or
MUFAs are
partially
hydrogenated.
Trans Fatty Acids
Functions of Fats
•
•
•
•
•
•
Increase satiety value of a meal.
Improve texture, flavor & aroma of foods.
Required for fat soluble vitamin absorption.
Provide the body’s major energy stores.
Cushion vital organs.
An essential structural component of cell
membranes.
• Provide insulation.
Fat: Dietary Recommendations
• 20-35% of total dietary Calories should
come from fats. This is the AMDR.
<7% should come from SFA. Limit trans fatty
acids.
• All excess Calories consumed whether from
carbohydrates, proteins, or fats are
converted to fat & stored in fat cells.
• Fat is the storage form of
energy in mammals.
Phospholipids (lecithin),
Part 1
• Non-Energy Yield: 0 Calories
per gram. Phospholipids are
non-energy-producing (noncaloric) lipid substances.
• Sources: Lecithin is found in
egg yolk and soy products
and is the most common
phospholipid consumed in the
diet.
Phospholipids (lecithin), Part 2
Functions:
1. Phospholipids like lecithin
are emulsifiers that allow
water soluble & fat soluble
substances to mix (like oil
& vinegar).
2. Lecithin provides choline
which is a component of
the neurochemical
acetylcholine.
3. Phospholipids are used to
make cell membranes.
Lecithin: A Phospholipid
Actual
Structure of
Lecithin
Cell Membrane
Sterols
Cholesterol is the most popular dietary sterol
Non-Energy Yield: Noncaloric, 0
Calories/gram
Sources of Cholesterol:
1. Exogenous: From outside the body.
Cholesterol is made by animals. It is only
found in animal foods & byproducts.
2. Endogenous: Made inside the human body.
Exogenous Sources
• Egg yolk provides ~275 mg each.
• Organ meats & crustaceans such as
crab, shrimp & lobster provide ~190
mg per 3 ounces.
• Much smaller amounts are in the fat
portions of animal meats & products
like milk.
Endogenous Sources
• Cholesterol is a very important
molecule in the body.
• Cholesterol is made inside the human
body, primarily in the liver, from SFA.
• Usually about 1 gram (1,000
milligrams) of cholesterol per day is
produced in the body.
• It is a very waxy substance.
Cholesterol is used to make …
Part 1
Cholesterol is used to make …
Part 2
• Myelin sheath that covers nerve cells.
• Cell membranes.
Cholesterol Recommendation
• Cholesterol can be deposited in the
artery walls leading to plaque
buildup & heart disease.
• To maintain heart health, the dietary
recommendation is to limit intake to
< 300 mg/day.
• To improve heart health, limit intake
to < 200mg/day.
Some
Summary Points, Part 1
• Fats/Lipids are organic compounds.
• Fats/Lipids are categorized as triglycerides,
phospholipids, and sterols.
• Triglycerides provide 9 Calories per gram.
• Triglycerides contains fatty acids that are categorized
as SFA, MUFA, & PUFA.
• There are 2 EFAs that are PUFAs (linoleic acid and
alpha-linolenic acid).
• AMDRs, omega 6 and 3 fatty acids
• Triglycerides have many important functions.
Some
Summary Points, Part 2
• Consume 20-35% of Calories from fats & limit SFAs
to <7% of Calories.
• Phospholipids like lecithin, emulsify and help make
up cell membranes and acetylcholine.
• Cholesterol is found in animal foods. It is not
essential and can be made in the liver. It has many
important functions in the body but intake should be
limited to less than 300 mg/day.
References for this presentation are
the same as those for this topic found
in module 1 of the textbook