chapter 4 power point

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Chapter 4 Lecture

Chapter 4:Fats: Essential Energy-Supplying Nutrients

Learning Objectives

1. Compare and contrast the three types of lipids found in foods.

2. Discuss how the level of saturation of a fatty acid affects its shape and the form it takes.

3. Explain the health benefits and dietary sources of the essential fatty acids.

4. List five functions of fat.

5. Describe the steps involved in fat digestion, absorption, and transport.


Learning Objectives

6. Identify the dietary recommendations for intakes of total fat, saturated fat, trans fats, and the essential fatty acids.

7. Identify common food sources of less healthful versus more healthful fats.

8. Summarize our current understanding of the relationship between intake of dietary fats and the development of cardiovascular disease and cancer.


What Are Fats?

• Fats are one type of a group of substances called lipids. • Other types of lipids are triglycerides,

phospholipids, and sterols.• Lipids are distinguished by the fact that they are

insoluble (do not dissolve) in water.


Where Can We Find Fats?


See Fats In Foods Link separate from this power

point.

Triglycerides

• Triglycerides are composed of:• Three fatty acid molecules

• Fatty acids are long chains of carbon atoms surrounded by hydrogen atoms.

• One glycerol molecule• Glycerol is a three-carbon alcohol that is the

backbone of a triglyceride.


Triglycerides


Triglycerides

• Fatty acids can differ in: • Level of saturation (hydrogen bonds)

• Saturation refers to how many hydrogen atoms surround each carbon.

• Shape• Straight chains of fatty acids form solids (butter,

lard), while kinked chains are less solid and usually exist as fluids at room temperature (oils).


Triglycerides

• Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain.

• Monounsaturated fatty acids lack hydrogen atoms in one specific location.

• Polyunsaturated fatty acids lack hydrogen atoms in multiple locations.


Triglycerides


Triglycerides

• The shape of a triglyceride is determined by the saturation of the carbon chains.

• Saturated fatty acids can pack tightly together and are solid at room temperature.• For example, animal fats, butter, and lard are

high in saturated fatty acids.


Triglycerides

• Unsaturated fatty acids: • Do not stack together well• Are liquid at room temperature• Are present in plant oils • May be:

• Monounsaturated – one double bond• Polyunsaturated – more than one double bond


Triglcerides


Triglycerides

• Hydrogenation: the addition of hydrogen atoms to unsaturated fatty acids• Converts liquid fats (oils) into a more solid

form• Used to create margarine from oils• Often creates trans fatty acids


Triglycerides

• Trans fatty acids:• Are detrimental to health• Change the way our cell membranes function• Reduce the removal of cholesterol from the

blood• Any partially hydrogenated oil (PHO) listed on a

nutritional label is usually a trans fat.


Triglycerides

• Essential fatty acids• Two fatty acids cannot be made in the body and

must be obtained from food.• Linoleic acid (omega-6 fatty acid), found in

vegetable and nut oils• Source of EPA and DHA

• Alpha-linolenic acid (omega-3 fatty acid), found in vegetables, fish, and fish oils


Phospholipids

• Phospholipids are:• Composed of glycerol, two fatty acids, and

phosphate• Soluble in water• Manufactured in our bodies so they are not

required in our diet• A critical component of cell membranes


Phospholipids


Sterols

• Sterols: lipids containing multiple rings of carbon atoms• Are essential components of cell membranes

and many hormones• Are manufactured in our bodies and therefore

are not essential components of our diet• Include cholesterol


Sterol Structure


Why Do We Need to Eat Fats?

• Energy• Fats provide 9 kcal per gram.• Fat is very energy-dense.• 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.



• Fat-soluble vitamins• Vitamins A, D, E, and K are soluble in fat; fat

is required for their transport.• Fats are essential to many body functions.

• Cell membrane structure• Protection of internal organs• Insulation to retain body heat



• Fats provide flavor and texture to foods.• Fats contribute to making us feel satiated

because:• Fats are more energy-dense than

carbohydrates or protein.• Fats take longer to digest.


Digestion of Fats


See Fat Digestion Link separate from this power

point.

Digestion of Fats

• Fats are not digested and absorbed easily because they are insoluble in water.

• Enzymes in the mouth and stomach can digest only about 10% of the fats present.

• The gallbladder, liver, and pancreas assist in fat breakdown.

• Most digestion of fats begins in the small intestine.


Digestion of Fats


Digestion of Fats

• As fat enters the small intestine:• Bile is produced by the liver and stored in the

gallbladder.• Bile is secreted from the gallbladder into the

small intestine.• Bile disperses fat into smaller fat droplets.• Pancreatic enzymes break fat into two fatty

acids and a monoglyceride.


Digestion of Fats

• Fatty acids are arranged as lipoproteins for absorption and transport.

• Chylomicron: a lipoprotein produced by cells lining the small intestine• Composed of fatty acids surrounded by

phospholipids and proteins• Soluble in water• Chylomicrons transport consumed fats to the

bloodstream


Structure of a Lipoprotein


Absorption of Fats


See Lipid AbsorptionLink separate from this power point.

Absorption of Fats

• Chylomicrons are absorbed by cells of the small intestine, then they:• Travel through the lymphatic system• Are transferred to the bloodstream

• Short-chain fatty acids are absorbed directly into the bloodstream.


Absorption of Fats

• After entering body cells, triglycerides can be:• Used immediately for energy• Used to make lipid-containing compounds

(e.g., some hormones, bile)• Stored in muscle or adipose tissue


How Much Fat Should We Eat?

• The Acceptable Macronutrient Distribution Range (AMDR) for fat:• 20–35% of calories should be from fat

• Athletes and highly active people may need more energy from carbohydrates but 20–35% of calories still should be from fat.

• Very low fat diets (less than 20% of total calories) do not provide additional health or performance benefits.



• The Acceptable Macronutrient Distribution Range (AMDR) for essential fatty acids:• 5–10% of energy from linoleic acid• 0.6–1.2% of energy from alpha-linolenic acid



• The type of fat consumed is important.• Saturated fat should be between 5% and 6%

of total energy• Trans fatty acids should be reduced to the

absolute minimum.• Most fat in our diets should come from

unsaturated fats


Choosing Foods with Helpful Fats

• Visible fats• Fats we knowingly add to foods• Butter, cream, mayonnaise, dressings

• Invisible fats• Fats hidden in foods• Naturally occurring or added during

processing


Food Sources of Fats


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point.

http://media.pearsoncmg.com/bc/bc_0media_hk/nutritools/html5/BuildASalad/index.html

Food Sources of Beneficial Fats

• Eat more fish.• Mercury and PCB concerns

• Choose plants.• Opt for low-fat.


Omega-3 Fatty Acid Content of Selected Foods


Fat Comparison of Selected Foods


What Role Do Fats Play in Chronic Disease?

• Cardiovascular disease• Dysfunction of the heart or blood vessels• Coronary artery disease• Stroke• Hypertension

• Dietary fats play an important role in cardiovascular disease.


Cardiovascular Disease

• Blood lipids include:• Chylomicrons• VLDLs: very-low-density lipoproteins• LDLs: low-density lipoproteins

• "Bad cholesterol"

• HDLs: high-density lipoproteins• "Good cholesterol"


Lipoproteins


Composition of Lipoproteins



• Diets high in saturated fats, simple sugars and extra energy tend to increase VLDLs.

• Diets high in saturated and trans fats tend to increase LDL levels.

• Diets high in omega-3 fatty acids tend to increase HDL levels.

• Diets high in saturated and trans fats tend to increase Cholesterol levels.



• Trans fatty acids:• Can raise blood LDL levels as much as

saturated fat• Are abundant in hydrogenated vegetable oils

(margarine, vegetable oil spreads)• Should be reduced to the absolute minimum

in the diet



• Risk factors for cardiovascular disease include:• Being overweight• Physical inactivity• Smoking• High blood pressure• Diabetes
