Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 5 Lipids, or Fats.

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

Chapter 5

Lipids, or Fats


Objectives

• State functions of fats in body

• Identify sources of dietary fats

• Explain common classifications of fats

• Describe disease conditions with which excessive use of fats are associated


Facts

• Fats– Belong to group of organic compounds

• Lipids

– Greasy substances

– Insoluble in water

• Each gram of fat contains 9 calories

• Composed of carbon, hydrogen, and oxygen– Lower proportion of oxygen than carbohydrates


Functions

• Provide energy

• Carry fat-soluble vitamins

• Supply essential fatty acids

• Protect and support organs and bones

• Insulate from cold

• Provide satiety after meals


Food Sources

• Animal– Fatty meats and fish

– Dairy products

– Egg yolks

(continues)


Food Sources

• Plant– Cooking oils and margarine

– Nuts

– Avocados

– Coconut

– Cocoa butter


Visible and Invisible Fats

• Visible– Fats in foods that are

purchased and used as fats

– E.g., butter, margarine, lard, cooking oils

• Invisible– Fats not immediately

noticeable

– E.g., egg yolks, cheese, cream, salad dressings


Stop and Share

• Consider the following scenario:– You are the nurse teaching a class about nutrition. A client

asks about ways to decrease the amount of fat in his diet. What are some suggestions you can offer him?

(continues)


Stop and Share

• Beware of hidden fats

• Decrease amount of fatty meats– E.g., bacon, sausage, luncheon meats

– Use lean meats, instead

• Use low-fat or skim milk

• Use egg whites instead of yolks when possible– Egg white contains no fat

• Almost entirely protein and water


Classification

• Triglycerides– Most lipids in body

• 95 percent

– Composed of three fatty acids attached to framework of glycerol

• Phospholipids

• Sterols– Cholesterol


Fatty Acid Classification

• May be classified by body’s need for them:– Essential fatty acids (EFAs)

– Nonessential

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Fatty Acid Classification

• May be classified by degree of saturation with hydrogen atoms:– Saturated

– Unsaturated• Monounsaturated

• Polyunsaturated


Essential Fatty Acids

• Cannot be synthesized by body

• Must be obtained from diet

• Two families:– Omega-3

– Omega-6


Nonessential Fatty Acids

• Can be synthesized by body

• Omega-9 fatty acids can be synthesized in body when EFAs present– Previously thought to be essential


Saturated Fats

• Each of its carbon atoms carries all hydrogen atoms possible

• In general, animal foods contain more saturated fatty acids than unsaturated

• Usually solid at room temperature

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Saturated Fats

• E.g., meat, poultry, egg yolks, whole milk, whole milk cheeses, cream, ice cream, butter, chocolate, coconut, palm oil


Monounsaturated Fats

• Have one place among carbon atoms where there are fewer hydrogen atoms attached than in saturated fats

• Lower low-density lipoprotein (LDL or “bad” cholesterol) when they replace saturated fat in one’s diet

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Monounsaturated Fats

• E.g., olive oil, canola oil, avocados, cashew nuts

• Recommend 15 percent of total daily calories


Polyunsaturated Fats

• Have two or more places among carbon atoms where there are fewer hydrogen atoms attached than in saturated fats

• E.g., cooking oils made from sunflower, safflower, sesame seeds, corn, or soybeans; soft margarines with liquid vegetable oil as major ingredient; fish

(continues)



• Foods containing high proportions of polyunsaturated fats– Usually soft or oily

• Omega-3– Lower risk of heart disease

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• Omega-6– Lower cholesterol

• Recommend 8 percent or less of total daily calories


Trans Fatty Acids (TFAs)

• Produced when hydrogen atoms added to monounsaturated or polyunsaturated fats to produce semi-solid product– E.g., margarine, shortening

• Raise LDL and total cholesterol

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TFAs

• Major sources:– Baked goods

– Restaurant foods


Hydrogenated Fats

• Polyunsaturated vegetable oils to which hydrogen has been added commercially to make them solid at room temperature

• Hydrogenation– Process that turns polyunsaturated vegetable oils into

saturated fats

– E.g., margarine, shortening


Cholesterol

• Sterol– Fatlike substance

• Exists in animal foods and body cells

• Does not exist in plant foods

(continues)


Cholesterol

• Essential for synthesis of bile, sex hormones, cortisone, and vitamin D

• Needed by every cell in body, but manufactured by liver


Stop and Share

• Consider the following scenario:– Your client has been diagnosed with a high cholesterol

level greater than 200 mg per dL. Answer the following questions:

• What risks are associated with a high cholesterol level?

• What can be done to lower a high cholesterol level?

(continues)


Stop and Share

• High cholesterol leads to atherosclerosis– Cardiovascular disease in which plaque forms on inside of

artery walls• Plaque

– Fatty deposits containing cholesterol and other substances

– Can lead to heart attacks and strokes

(continues)


Stop and Share

• Reduce amount of total fat, saturated fats, and cholesterol

• Increase monounsaturated fats, lose weight, and exercise

• Increase consumption of soluble dietary fiber

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Stop and Share

• Do not exceed daily cholesterol intake of 300 mg

• In some cases, have medication prescribed


Digestion and Absorption

• 95 percent of ingested fats digested

• Chemical digestion of fats occurs mainly in small intestine

• No digestion of fats occurs in mouth

• Slight digestion in stomach where gastric lipase acts on emulsified fats

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Digestion and Absorption

• Digestion in small intestine– Bile emulsifies fats

– Lipase reduces fats to fatty acids and glycerol

– Absorption occurs through villi of small intestine


Lipoproteins

• Bile joins with products of fat digestion to carry fat

• Protein combines with final products of fat digestion to form lipoproteins

• Lipoproteins carry fat in blood to body cells

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Lipoproteins

• Classified according to mobility and density

• Types:– Chylomicrons

– Very-low-density lipoproteins (VLDLs)

– LDLs

– High-density lipoproteins (HDLs)


Chylomicron

• First lipoprotein identified after eating

• Largest lipoprotein– Yet lightest in weight

• Composed of 80 to 90 percent triglycerides


VLDLs

• Made by liver to transport lipids throughout body

• Composed of 55 to 65 percent triglycerides

• Carry triglycerides and other lipids to all cells

• As VLDL lose triglycerides, pick up cholesterol from other lipoproteins in blood– Become LDL


LDLs

• Composed of 45 percent cholesterol with few triglycerides

• Carry most of blood cholesterol from liver to cells

• Level greater than 130 mg per dL– Considered to contribute to atherosclerosis

• “Bad” cholesterol


HDLs

• Carry cholesterol from cells to liver for eventual excretion

• Level of 60 mg per dL or more– Considered to reduce risk of heart disease

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HDLs

• Increase by doing the following:– Exercising

– Maintaining desirable weight

– Giving up smoking

• “Good” cholesterol


Metabolism and Elimination

• Liver controls fat metabolism

• In cells, fatty acids broken down to carbon dioxide and water– Releasing energy

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Metabolism and Elimination

• Excess fat stored as adipose tissue

• Carbon dioxide and water removed from body by circulatory, respiratory, and excretory systems


Stop and Share

• Consider the following scenario:– Your client asks you about a new dietary supplement that

advertisers claim provides essential nutrients and lowers cholesterol “naturally.” How do you advise your client?

(continues)


Stop and Share

• Any new dietary supplement with nutritional claim should be evaluated carefully

• If item not included in Recommended Daily Allowance (RDA) or DRI, assume medical research has not determined it essential

• Ingestion of dietary supplements of unknown value could be damaging to one’s health


Phospholipid

• Found in both plant and animal foods

• Synthesized in liver

• Natural emulsifier that helps transport fat in bloodstream

• E.g., lecithin


Fat Alternatives

• Olestra– Made from carbohydrates and fat

– FDA approved for use in snack food

– Food labels must indicate that it “inhibits absorption of some vitamins and other nutrients”

– Should be used in moderation

– Contains no calories

– Can cause cramps and diarrhea

(continues)


Fat Alternatives

• Simplesse– Made from egg white or milk protein

– Can be used only in cold foods

– Not available for home use

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Fat Alternatives

• Oatrim– Carbohydrate-based

• Derived from oat fiber

– Can be used in baking• But not frying

– Provides calories• But less than fat


Dietary Requirements

• Deficiency symptoms occur when fats provide less than 10 percent of total daily calories

• Food and Nutrition Board’s Committee on Diet and Health recommends that people reduce fat intake to 30 percent of total calories

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Dietary Requirements

• American Heart Association’s newest recommendation:– Consume ≤ 7 percent of saturated fats, 8 percent

polyunsaturated fats, and 15 percent monounsaturated fats

• At present, 36 percent of calories in U.S. diets derived from fats


Conclusion

• Fats provide energy, carry essential fatty acids and fat-soluble vitamins, protect organs and bones, insulate from cold, and provide satiety after meals

• Fats are composed of carbon, hydrogen, and oxygen– Found in both animal and plant foods

(continues)


Conclusion

• Each gram of fat provides 9 calories

• Digestion occurs primarily in small intestines

• Excess of fat in diet can result in obesity, heart disease, or cancer

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 5 Lipids, or Fats.

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