fats and - cengage...fatty acid families of omega-6 (also called n-6 fatty acids) and omega-3 fatty...

Fats andCholesterol in Health

Nutrition Scoreboard

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1 It is currently recommended that adults consumediets providing less than 30% of calories from fat.

2 The types of fat consumed are more important tohealth than is total fat intake.

3 Cholesterol is present in every food.

4 Saturated fat intake has a much stronger influenceon blood cholesterol levels than does cholesterolintake.

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[ KEY CONCEPTS AND FACTS ]

• Fats are our most concen-trated source of food energy. They supply 9 calo-ries per gram.

• Dietary fats “carry” theessential fatty acids, fat-soluble vitamins, andhealthful phytochemicalsalong with them in foods.

• Fats are not created equal.Some types of fat have posi-

tive effects, and somehave negative effects onhealth.

• Saturated fats and transfats raise blood choles-terol levels more thandoes dietary cholesterol orany other type of fat.

Answers to Nutrition Scoreboard

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1 Recommendations for fat intake have changed! Theacceptable range of fat intake is now 20-35% oftotal calories.

2 The types of fat consumed are more important tohealth than the total amount of fat.1

3 Cholesterol is present only in animal products.

4 Saturated fat, which is found primarily in animalproducts, raises blood cholesterol levels a good dealmore than does dietary cholesterol.

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Changing Views about Fat Intake and HealthScientific evidence and opinions related to the effects of fat on health have changedsubstantially in recent years—and so have recommendations about fat intake. In thepast, it was recommended that Americans aim for diets providing less than 30% oftotal calories from fat. Evidence indicating that the type of fat consumed is moreimportant to health than is total fat intake has changed this advice. The watchwordsfor thinking about fat have become “not all fats are created equal: some are betterfor you than others.” American adults are being urged to select food sources of“healthy” or “good” fats while keeping fat intake within the range of 20–35% oftotal caloric intake. Concerns that high-fat diets encourage the development of obe-sity have been eased by studies demonstrating that excessive caloric intakes—andnot just diets high in fat—are related to weight gain.2

New recommendations regarding fat intake do not encourage increased fat con-sumption. Rather, they emphasize that healthy diets include certain types of fat, andthat total caloric intake and physical activity are the most important components ofweight management. Diets providing as low as 20% of calories from fat, and thoseproviding 30–35%, can be healthy—depending on the types of fat consumed andthe quality of the rest of the diet.3 This unit provides facts about fats, explains thereasons behind recent changes in recommendations for fat intake, and addresses thepractical meaning of it all.

Facts about FatsFats are a group of substances found in food. They have one major property in com-mon: they are not soluble (or, in other words, will not dissolve) in water. If you haveever tried to mix vinegar and oil when making salad dressing, you have observed theprinciple of water and fat solubility firsthand.

Fats are actually a subcategory of the fat-soluble substances known as lipids.Lipids include fats, oils, and cholesterol. Dietary fats such as butter, margarine, andshortening are often distinguished from oils by their property of being solid at room

lipidsCompounds that are insolublein water and soluble in fat.Triglycerides, saturated andunsaturated fats, and essentialfatty acids are examples oflipids, or “fats.”

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temperature. This physical difference between fats and oils is due to their chemicalstructures.

Contributions of Dietary Fats

Fats in Foods Supply Energy and Fat-Soluble Nutrients] Fats include theessential fatty acids (linoleic acid and alpha-linolenic acid) and provide the fat-soluble vitamins D, E, K, and A (the “deka” vitamins). So, part of the reason weneed fats in our diet is to get a supply of the essential nutrients they contain (Table18.1). Diets containing little fat (less than 20% of total calories) often fall short ondelivering adequate amounts of essential fatty acids and fat-soluble vitamins.4

Fats Increase the Flavor and Palatability of Foods] Although “pure” fats bythemselves tend to be tasteless, they absorb and retain the flavor of substances thatsurround them. Thus, fats in meats and other foods pick up flavors from their envi-ronment and give those flavors to the food. This characteristic of fat is why butter,if placed next to the garlic in the refrigerator, tastes like garlic.

Fats Contribute to the Sensation of Feeling Full] As they should, at 9 calo-ries per gram! Fats tend to stay in the stomach longer than carbohydrates or pro-teins and are absorbed over a longer period of time. That’s why foods with fat “stickto your ribs.”5

A Crucial Role of Fat Is to Serve as a Component of Cell Membranes]Some types of fats give cell membranes flexibility and help regulate the transfer ofnutrients into and out of cells.6

Excess Dietary Fat, Carbohydrates, and Protein Are Stored as FatFats in the body include those consumed in the diet and those produced from car-bohydrates and proteins. Humans eat only a few times a day, but we need energythroughout the day. To ensure a constant supply of energy, the body converts car-bohydrates and proteins, which have been supplied from foods and are not used tomeet immediate needs, to storage forms of energy. Some of the excess carbohydrateand protein is converted to glycogen, the storage form of glucose under normal cir-cumstances, but most of the excess is changed to fat and stored in fat cells (Illustra-tion 18.1).

Body fat is not just skin deep. Fat is also located around organs such as the kid-neys and heart. It’s there to cushion and protect the organs and keep them insulated.Cold-water swimmers can attest to the effectiveness of fat as an insulation material.They purposefully build up body fat stores because they need the extra layer of insu-lation (Illustration 18.2).

Fats Come in Many VarietiesThere are many types of fat in food and our bodies (Table 18.2). Of primary impor-tance are triglycerides (or “triacylglycerols”), saturated and unsaturated fats, andcholesterol (for definitions, see Table 18.3). The different types of fats have differ-ent effects on health.

TABLE 18.1

ROLES OF DIETARY FAT.

• Provides a concen-trated source of energy

• Carries the essentialfatty acids, the fat-soluble vitamins, andcertain phytochemicals

• Increases the flavorand palatability offoods

• Provides sustainedrelief from hunger

• Serves as a componentof cell membranes

essential fatty acidsComponents of fats (linoleicacid—pronounced lynn-oh-lay-ick and alpha-linolenic acid—lynn-oh-len-ick) required inthe diet.

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Triglycerides, which consist of oneglycerol unit (a glucose-like substance) andthree fatty acids (Illustration 18.3), makeup 98% of our dietary fat intake and thevast majority of our body’s fat stores.Triglycerides are transported in bloodattached to protein carriers and are used bycells for energy formation and tissue main-tenance. A minority of fats take the form ofdiglycerides (glycerol plus two fatty acids)and monoglycerides (glycerol and one fattyacid). Diglycerides are present in some oilsand small amounts are used in food prod-ucts as emulsifiers—or to increase theblending of fat- and water-soluble sub-stances. Monoglycerides are present insmall amounts in some oils; we don’t con-sume very much of them in foods.

As far as health is concerned, the glyc-erol component of fat is relatively unim-portant. It’s the fatty acids that influencewhat the body does with the fat we eat; andthey are responsible, in part, for how fataffects health. Many different types of fattyacids are found in triglycerides. You’veheard of the major ones: those that makefat “saturated” or “unsaturated.”

Saturated and Unsaturated Fats] Fatty acids found in fats consist primarily ofhydrogen atoms attached to carbon atoms (Illustration 18.4). When the carbons areattached to as many hydrogens as possible, the fatty acid is “saturated”—that is,saturated with hydrogen. Saturated fats tend to be solid at room temperature.Except for palm and coconut oil, only animal products are rich in saturated fats(Illustration 18.5 on p. 18–6).7 Fatty acids that contain fewer hydrogens than themaximum are “unsaturated.” They tend to be liquid at room temperature. By andlarge, plant foods are the best sources of unsaturated fats.

Unsaturated fats are classified by their degree of unsaturation. If only one carbon-carbon bond in the fatty acid is unsaturated, the fat is called “monounsatu-rated.” If two or more carbon-carbon bonds are unsaturated with hydrogen, the fatqualifies as “polyunsaturated.”

The Omega-3 and Omega-6 Fatty Acids The essential fatty acids linoleic acid and alpha-linolenic acid are members of thefatty acid families of omega-6 (also called n-6 fatty acids) and omega-3 fatty acids(also known as n-3 fatty acids), respectively. Both are polyunsaturated, can be usedas a source of energy, and are stored in fat tissue. Because they are essential, bothlinoleic and alpha-linolenic acid are required in the diet.

Linoleic acid is required for growth, maintenance of healthy skin, and normalfunctioning of the reproductive system. It is a component of all cell membranes andis found in particularly high amounts in nerves and the brain. A number of biolog-ically active compounds, produced in the body, that participate in regulation ofblood pressure and blood clotting are derived from linoleic acid. The major foodsources of linoleic acid are sunflower, safflower, corn, and soybean oils.

Illustration 18.1A close look at fat cells(color-enhancedmicrophotograph).

Illustration 18.2Although their body fat stores don’t fitthe image of the superathlete, cold-water swimmers need the fat to helpstay warm. Pictured here is the Englishswimmer Mike Read, who had swum theEnglish Channel 20 times by age 39.

TABLE 18.2

BASIC FACTS ABOUT THETYPES OF FAT.

Fats can be:

• Monoglycerides

• Diglycerides

• Triglycerides

Fats can be:

• Saturated

• Monounsaturated

• Polyunsaturated

Unsaturated fats come in:

• “Cis” forms

• “Trans” forms

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Illustration 18.4A look at the differencebetween a saturated and anunsaturated fatty acid.

TABLE 18.3

A GLOSSARY OF FATS.

Triglycerides: Fats in which the glycerol molecule has three fatty acids attached to it; alsocalled triacylglycerol. Triglycerides are the most common type of fat in foods and in bodyfat stores.

Saturated fats: Molecules of fat in which adjacent carbons within fatty acids are linkedonly by single bonds. The carbons are “saturated” with hydrogens; that is, they are attachedto the maximum possible number of hydrogens. Saturated fats tend to be solid at roomtemperature. Animal products and palm and coconut oil are sources of saturated fats.

Unsaturated fats: Molecules of fat in which adjacent carbons are linked by one or moredouble bonds. The carbons are not saturated with hydrogens; that is, they are attached tofewer than the maximum possible number of hydrogens. Unsaturated fats tend to be liquidat room temperature and are found in plants, vegetable oils, meats, and dairy products.

Glycerol: A syrupy, colorless liquid component of fats that is soluble in water. It is similar toglucose in chemical structure.

Cholesterol: A fat-soluble, colorless liquid found in animals but not in plants. Cholesterol isused by the body to form hormones such as testosterone and estrogen and is a componentof animal cell membranes.

Diglyceride: A fat in which the glycerol molecule has two fatty acids attached to it; alsocalled diacylglycerol.

Monoglyceride: A fat in which the glycerol molecule has one fatty acid attached to it; alsocalled monoacylglycerol.

Monounsaturated fats: Fats that contain a fatty acid in which one carbon-carbon bond isnot saturated with hydrogen.

Polyunsaturated fats: Fats that contain a fatty acid in which two or more carbon-carbonbonds are not saturated with hydrogen.

Glycerol + 3 fatty acids = Triglyceride+

+

+

Illustration 18.3A triglyceride.

Two hydrogens are missing from each of these carbon-carbon links, making the fatty acid polyunsaturated. With fewer hydrogens to attach to, these carbons are doubly bonded to each other. Monounsaturated fatty acids have only one carbon-carbon bond that is "unsaturated" with hydrogen atoms.

CH CH CH CH

OxygenCarbon

Hydrogen

CH3

CH CH

Saturated fatty acid

Monounsaturated fatty acid

Polyunsaturated fatty acid

Oxygen

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Alpha-linolenic acid, EPA (eicosapentaenoic acid—pronounced e-co-sah-pent-tah-no-ick) and DHA (docosahexaenoic acid: dough-cos-ah-hex-ah-no-ick) are pri-mary members of the omega-3 fatty acid family. Alpha-linolenic acid is an essentialnutrient, but EPA and DHA are not. These two members of the omega-3 fatty acidfamily can be produced in the body from alpha-linolenic acid. However, the con-

Illustration 18.5Fat profiles of selected foods.

DAIRY PRODUCTS

Brick cheese

Cheddar cheese

Cottage cheese

American cheese

Whole milk

Butter

Saturated Monounsaturated Polyunsaturated

PERCENTAGE FATTY ACID COMPOSITION

HUMAN MILK

67 30 3

65 31 4

65 31 4

48 40 12

EGG

OILS AND MARGARINES

(medium)

Canola oil

Coconut oil

Corn oil

Corn oil margarine

Flaxseed oil

Olive oil

Palm oil

Peanut oil

Soybean oil

Soybean oil margarine

Sunflower oil

6 58 36

92 6 2

13 25 62

17 61 22

14 77 9

4818 34

52 38 10

15 25 60

22 50 28

11 21 68

MEATSHamburger (21% fat)

Chicken, roasted (no skin)

Pork chop

Turkey, roasted 352540

39 49 12

26 46 28

53 43 4

NUTS AND SEEDSCashews

Macadamia Nuts

Peanuts, dry-roasted

Peanut butter

Sunflower seeds (dried)

21 62 17

16 46 2

15 52 33

18 51 32

11 20 69

37 48 15

67 30 3

30 367

30 367

9 18 73

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version of this essential fatty acid to EPA and DHA is slow and results in the avail-ability of relatively little EPA and DHA.9 Alpha-linolenic acid is a structural com-ponent of all cell membranes and is found in high amounts in cells of the brain andeyes. Alpha-linolenic acid is also involved in the formation of biologicallyactive compounds used in regulating blood pressure and blood clotting;but these compounds have the opposite effect on the blood pressureand blood clotting, as do linoleic acid derivatives.10 Omega 3-fattyacids are found in a few foods such as walnuts, flaxseed, canola oil, andsoybeans in the form of alpha-linolenic acid. The most beneficial sourcesof omega-3 fatty acids, however, are marine oils—due to their contentof DHA and EPA.11 These two omega-3 fatty acids play importantroles in disease prevention and health promotion.

Omega-3 fatty acids are not just good fats,they affect heart health in positive ways.

—Penny Kris-Etherton, Distinguished Professor of Nutrition12

The Omega-3 Fatty Acids and Fish Oils] Many unsaturated fatscontain fatty acids with one or two unsaturated carbon-to-carbonbonds. DHA and EPA found in fish oils, however, stand out in that theycontain from 4 to 6 double bonds. This high level of unsaturation givesthese omega-3 fatty acids the unique property of being highly fluid evenat cold temperatures. This property allows the fatty acids to keep cellmembranes and fat-containing tissues in fish flexible in cold water. Fatty fish andfish that live in cold water contain the highest amounts of DHA and EPA (Table18.4).

In humans, DHA and EPA form biologically active compounds that reduceblood pressure and the tendency of blood to clot, and these properties confer healthadvantages. Regular consumption of these omega-3 fatty acids (two or more fish-containing meals per week) decreases the risk of heart attack, protects against irreg-ular heartbeat and sudden death, decreases plaque formation in arteries, lowers highblood pressure, and decreases the risk of stroke. Fish oil capsules are being increas-ingly viewed as potential sources of EPA and DHA. They are sometimes recom-mended for people at risk of heart disease and should be taken under medicalsupervision. High levels of fish oils (over 3 grams per day) can prevent blood fromclotting.14

Mercury in Fish and Fish Intake} Some fish contain high levels of mercury that canend up in fish oil supplements.15 Mercury was found to be a potent fungicide over100 years ago and was used extensively to prevent mold growth on crop seeds.Some of it ended up in streams, lakes, and oceans, and it lingers there for manydecades. Several catastrophic outbreaks of mercury poisoning due to consumptionof contaminated fish occurred during the mid-1900s and brought a halt to the useof mercury fungicides. Mercury is still found in some ocean and lake fish, but recentstudies indicate that the benefits of fish intake among people over the age of 40 faroutweigh risks related to mercury.16

Pregnant and breastfeeding women, and infants, are particularly susceptible tothe harmful effects of mercury and are advised to omit from their diets the top fourmercury-rich fish: shark, swordfish, king mackerel, and tilefish (also called goldensnapper and golden bass). Intake of all other fish should be limited to 12 ounces orless per week among pregnant and breastfeeding women, and to 2 ounces or less forchildren under the age of 6 years.17

Local advisories related to mercury levels of fish in lakes and streams are avail-able online (www.epa.gov/ost/fish), and advice on intake levels of fish caught in

Fishy eggs? An odd source of fish oilhas become part of North Americans’diets. Hens given feed with added codliver oil produce eggs with yolks con-taining 100 to 350 milligrams of highlyunsaturated omega-3 fatty acids.8

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them should be heeded. Large fish (longer than 20 inches) in general contain higherconcentrations of mercury than do smaller fish, so you may want to let the big onesget away . . .

Fish such as flounder, cod, trout, sole, salmon, tilapia, haddock, pollack, and“light” tuna—as well as shrimp and shellfish—generally contain low levels of mer-cury.18 Other sources of DHA and EPA include eggs enriched with omega-3 fattyacids. The American Heart Association recommends that adults consume two ormore servings of fish per week, or a total of 0.65 gram of DHA and EPA daily.19

Balancing Intake of Omega-6 and Omega-3 Fatty Acids] The ratio ofomega-6 to omega-3 fatty acid intake is important because the functions of one areadversely modified by the presence of disproportionately high amounts of the other.Although an exact ratio has not been agreed upon, it is thought that people shouldconsume omega-6 fatty acids and omega-3 fatty acids in a proportion of roughly 4(or less) to 1. Many Americans regularly consume vegetable oils but eat fish infre-quently. Consequently, the ratio between the intake of omega-6 and omega-3 fattyacids is over 9 to 1, indicating a need to increase intake of omega-3 fatty acids.20

Modifying FatsUnsaturated fats aren’t as stable as saturated fats. They are more likely to turn ran-cid with time and exposure to air and heat than are saturated fats. Additionally,solid fats are preferable to oils for some cooking applications. These problems withunsaturated fats have a solution. It’s called hydrogenation.

What’s Hydrogenation?] Hydrogenation is a process that adds hydrogen to liq-uid unsaturated fats, thereby making them more saturated and solid. The shelf life,cooking properties, and taste of vegetable oils are improved in the process. Hydro-genation has two drawbacks, however. Hydrogenated vegetable oils contain more

hydrogenationThe addition of hydrogen tounsaturated fatty acids.

TABLE 18.4

OMEGA-3 FATTY ACID (EPA & DHA) CONTENT OF SELECTED SEAFOODS.13

OMEGA-3FATTY ACIDS

(GRAMS)

SEAFOOD(31⁄2-OUNCE SERVING)

SEAFOOD(31⁄2-OUNCE SERVING

OMEGA-3FATTY ACIDS

(GRAMS)

Sardines in sardine oil 3.3Mackerel 2.6Salmon, Atlantic, farmed 2.2Lake trout 2.0Herring 1.8Salmon, Atlantic, wild 1.8Tuna, white, canned 1.7Salmon, sockeye 1.5Whitefish, lake 1.5Anchovies 1.4Salmon, chinook 1.4Bluefish 1.2Halibut 1.2Trout, rainbow, farmed 1.2Oysters 1.1Salmon, pink 1.0Trout, rainbow, wild 1.0Bass, striped 0.8Swordfish 0.8

Oysters 0.6Catfish 0.5Flounder 0.2Shrimp 0.5Halibut 0.5Pollock 0.5Scallops 0.5Whiting 0.5Carp 0.3Crab 0.3Pike, walleye 0.3Tuna, fresh 0.3Catfish, wild 0.2Clams 0.2Fish sticks 0.2Haddock 0.2Lobster 0.2Salmon, red 0.2Snapper, red 0.2

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saturated fat than the original oil. Corn oil, for example, contains only 6% satu-rated fats; but corn oil margarine has 17%. The other negative is that hydrogena-tion causes a change in the structure of the unsaturated fatty acids. Specifically,hydrogenation converts some unsaturated fats into trans fats.

Trans Fatty Acids] Up to 30% of the fatty acids in unsaturated fat molecules maybe converted from their naturally occurring “cis” to the “trans” form as a result ofhydrogenation.21 Fatty acids in this structural form raise blood cholesterol levelsmore than dietary cholesterol, saturated fats or any other type of fat do.22 The bulkof trans fat in our diet comes from hydrogenated vegetable oils. Trans fats are morestable and have a longer shelf life than other fats and are preferred for use in mar-garine, snack foods, bakery products, and fried foods (Table 18.5). Ruminant ani-mals like cows form some trans fat in the stomach; so milk, other dairy products,beef, and lamb contain small amounts of this type of fat. People in the United Statesconsume an average of 2.6% of total calories from trans fat, or 5.8 grams per day.23

It is recommended that Americans consume as little trans fats as possible,24 andnew nutrition information labeling requirements are making that easier to accom-plish. Nutrition Facts panels must include the trans fat content of food products byJanuary 1, 2006 (Illustration 18.6). The %DV column (for percent of Daily Value)will not be used for trans fats because there is no recommended level of intake. Prod-ucts labeled “trans fat–free” must contain less than 0.5 gram of both trans and sat-urated fats. It is expected that the requirement to label the trans fat content of foodproducts will increase the number of foods labeled “trans fat–free” and “no transfat” (Illustration 18.7) and decrease its use in foods. Food companies are busy devel-oping other ways to produce foods without them.25

Checking Out CholesterolCholesterol is a lipid found only in animal products.It is tasteless and odorless and contained in both thelean and fat parts of animal products. Table 18.6 listssome sources of cholesterol. Plants don’t containcholesterol because they can’t produce it and don’tneed it to function and grow normally.

Sources of CholesterolThe cholesterol used by the body comes from twosources. Most (about two-thirds) of the cholesterolavailable to the body is produced by the liver. Therest comes from the diet (Illustration 18.8). Becausethe liver produces cholesterol from other sub-stances in our diet, it does not qualify as an essen-tial nutrient.

The Contributions of CholesterolWould you be surprised to learn that cholesterol:

• is found in every cell in your body?

• serves as the building block for estrogen,testosterone, and the vitamin D that is pro-duced in your skin upon exposure to sunlight?

trans fatsUnsaturated fatty acids in fatsthat contain atoms of hydro-gen attached to opposite sidesof carbons joined by a doublebond:

H–C�C�

H H H–C�C–

Trans fatty Cis fattyacid acid

Fats containing fatty acids inthe trans form are generallyreferred to as trans fats. Cisfatty acids are the most com-mon, naturally occurring formof unsaturated fatty acids.They contain hydrogenslocated on the same side ofdoubly bonded carbons.

TABLE 18.5

TRANS FATTY ACID CONTENT OF FOOD PRODUCTS. Values may change as companies lower the trans fat content of foods.

FOOD TRANS FATTY ACIDS (GRAMS)

Kentucky Fried Chicken pot pie 8

French fries, large serving 4–7

Cake doughnut 6

Breaded fish sticks, 3 5

Margarine, 1 tbs 4

Dutch apple pie 3–4

Wheat crackers 3

Chocolate chip cookie 2

Snack crackers,1 2 oz 2

Shortening, 1 tbs 1

Tub margarine, 1 tbs 1

Butter, 1 tbs 0

“No trans fat” margarine 0

Olive oil 0

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• is a major component of nerves and the brain?

• cannot be used for energy (so it provides no calories)?

The body has many uses for cholesterol (Table 18.7). It doesn’t just accumulate inarteries!

Fat SubstitutesThe fat content of processed foods can be partially or fully replaced by fat substi-tutes. Fat substitutes attempt to imitate the taste, texture, and cooking properties ofour favorite fats, but with fewer calories. Table 18.8 lists some of the more than 60products that are already on the market; others are under development. The degreeto which these products succeed in imitating the qualities of fat varies. Making the

Illustration 18.6Trans fat: the newest addi-tion to Nutrition Facts panels.

Nutrition FactsServing Size 1 EntreeServing Per Container 1

Amount Per ServingCalories 380 Calories from Fat 170

Total Fat 19g Saturated Fat 10g Trans Fat 2gCholesterol 85gSodium 810mgTotal Carbohydrate 33g Dietary Fiber 3g Sugars 5gProtein 20g

29%%Daily Value

50%

28%34%11%12%

Vitamin A 10% Vitamin C 0%Calcium 10% Iron 15%

Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower depending on your calorie needs:

Total Fat

Sat Fat

Cholesterol

Sodium

Total Carbohydrate

Dietary Fiber

Calories 2000 2500

Less Than

Less Than

Less Than

Less Than

65g

20g

300mg

2400mg

300g

25g

80g

25g

300mg

2400mg

375g

30g

Illustration 18.7Products that feature “notrans fats” and “transfat–free” labels.

TABLE 18.6

FOOD SOURCES OF CHOLESTEROL. Note that all the sources are animal products. Cholesterol in foods is a clear, oily liquidfound in the fat and lean portions of many animal products.

ANIMAL PRODUCT AMOUNT CHOLESTEROL(MILLIGRAMS)

Brain 3 oz 1746

Liver 3 oz 470

Egg 1 212

Veal 3 oz 128

Shrimp 3 oz 107

Prime rib 3 oz 80

Chicken (no skin) 3 oz 75

Turkey (no skin) 3 oz 65

Hamburger, regular 3 oz 64

Pork chop, lean 3 oz 60

Fish, baked (haddock, flounder) 3 oz 58

Ice cream 1 cup 56

Sausage 3 oz 55

Hamburger, lean 3 oz 50

Milk, whole 1 cup 34

Crab, boiled 3 oz 33

Lobster 3 oz 29

Cheese (cheddar) 1 oz 26

Milk, 2% 1 cup 22

Yogurt, low-fat 1 cup 17

Milk, 1% 1 cup 14

Butter 1 tsp 10

Milk, skim 1 cup 7

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perfect fat substitute is not an easy task. Not all of the fat substitutes that haveentered the marketplace have met the test of consumer acceptability.28

Are Fat Substitutes Safe?Consumers sometimes wonder about the safety of fat substitutes. Because most fatsubstitutes are derived from ingredients of food such as carbohydrates, protein, andvegetable oils, they are often assumed to be safe. Fat replacers that are made fromsubstances that do not occur naturally in foods must be tested for safety. Olean, anon-naturally occurring fat replacer that cannot be digested, was tested extensivelybefore being approved for use. It can cause diarrhea and oily stools if consumed inlarge amounts.29

Can Fat Substitutes Benefit Health?When substituted for foods containing saturated fats, fat substitutes may benefithealth by lowering blood cholesterol levels. Studies suggest that the use of foods con-taining fat substitutes reduces total fat consumption, but whether they lead to weightloss is controversial. So, although they may not be the answer to weight control, fatsubstitutes may provide part of the solution to high fat intakes and the health prob-lems related to them.30

Finding Out about the Fat Contentof Food

Not all of the fat in food is visible. To avoid being fooled, it helps to usea reference on the fat composition of foods. Table 18.9 lists the fat con-tent of common food sources of fat, including candy. Vegetables andfruits (except avocado and coconut) and grains are not listed becausethey contain relatively little fat. Other references can also be used, suchas the food composition tables in Appendix A, the Diet Analysis PlusProgram software, and the nutrition labels on food products.

TABLE 18.7

HOW THE BODY USESCHOLESTEROL.

• Cholesterol is a compo-nent of all cell mem-branes, the brain, andnerves.

• It is needed to produceestrogen, testosterone,and vitamin D.

TABLE 18.8

SOME FAT SUBSTITUTES.27

PROTEIN-BASED(1–2 CAL/G)

CARBOHYDRATE-BASED(0–4 CAL/G)

FAT-BASED(0–5 CAL/G) COMBINATIONS

Amalean I and II K-Blazer Benefat FitesseCrystaLean Proplus Caprenin NutrifatInstant Stellar Simplesse Olean ProlestraJuguarLitesseMaltrinN-LiteOat fiberOatrimOpta GradePure-gelSta-SlimSta-Lite

Fats 5%

Milk and milk products 15%

Meats 36%

Eggs(egg yolk)

29%

Otherfoods15%

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Illustration 18.8Food sources of cholesterol inthe U.S. diet.26

Percentages indicate the pro-portion of cholesterol eachtype of food contributes to the diet.

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Knowledge of the caloric and fat content of a food can be used to calculate thepercentage of calories provided by fat. For example, suppose that a slice of cherrypie provides 350 calories and 15 grams of fat. To calculate the percentage of fatcalories, multiply 15 grams by 9 (the number of calories in each gram of fat), dividethe result by 350 calories, and then multiply by 100:

15 grams fat � 9 calories/gram � 135 calories135 calories/350 � 0.39

0.39 � 100 � 39% of total calories from fat

Fat LabelingNutrition labeling regulations for fat require food manufacturers to adhere to stan-dard definitions of “low fat,” “fat-free,” and related terms used on food labels. Sim-ilarly, claims made about the cholesterol content of food products must comply withstandard definitions (Table 18.10, on page 18-14). If a claim is made about the fatcontent of a food, the Nutrition Facts panel must specify the food’s fat, saturatedfat, trans fat, and cholesterol content. If a claim is made about cholesterol content(and claims can be made only for products that normally contain cholesterol), thenutrition panel must also reveal the product’s fat and saturated fat content. To pre-vent the use of unrealistically small serving sizes as a way to appear to cut down ona product’s fat content, standard serving sizes must be used on food labels.

TABLE 18.9

THE FAT CONTENT OF SOME FOODS.

AMOUNTFOOD GRAMS PERCENTAGE OFTOTAL CALORIES FROM FAT

Fats and oilsButter 1 tsp 4.0 100%Margarine 1 tsp 4.0 100Oil 1 tsp 4.7 100Mayonnaise 1 tbs 11.0 99Heavy cream 1 tbs 5.5 93Salad dressing 1 tbs 6.0 83

Meats and fast foodsHot dog 1 (2 oz) 17.0 83Bologna 1 oz 8.0 80Sausage 4 links 18.0 77Bacon 3 pieces 9.0 74Salami 2 oz 11.0 68Pork steak 3 oz 18.0 62Hamburger, regular (20% fat) 3 oz 16.5 62Chicken, fried with skin 3 oz 14.0 53Big Mac 6.6 oz 31.4 52Quarter Pounder with cheese 6.8 oz 28.6 50Whopper 8.9 oz 32.0 48Steak (rib eye) 3 oz 9.9 47Hamburger, lean (10% fat) 3 oz 9.5 45Steak (T-bone), lean 3 oz 8.9 44Rabbit 3 oz 7.0 38Veggie pita 1 17.0 38Ranch chicken pita 1 18.0 34

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TABLE 18.9

THE FAT CONTENT OF SOME FOODS. (CONTINUED)

AMOUNTFOOD GRAMS PERCENTAGE OFTOTAL CALORIES FROM FAT

Meats and fast foods—continuedSteak (round), lean only 3 oz 5.2 29Chicken, baked without skin 3 oz 4.0 25Turkey wrap 1 9.0 24Hamburger, extra lean

(4% fat) 3 oz 2.3 23Venison 3 oz 2.7 18Subway, club 6" 5.0 14Flounder, baked 3 oz 1.0 13Subway, veggie 6" 3.0 11Shrimp, boiled 3 oz 1.0 10

Milk and milk productsCheddar cheese 1 oz 9.5 74American cheese 1 oz 6.0 66Milk, whole 1 cup 8.5 49Cottage cheese, regular 1⁄2 cup 5.1 39Milk, 2% 1 cup 5.0 32Milk, 1% 1 cup 2.7 24Cottage cheese, 1% fat 1⁄2 cup 1.2 13Milk, skim 1 cup 0.4 4Yogurt, frozen 3⁄4 cup 0.0–6.6 0–3

OtherOlives 4 medium 1.5 90Avocado 1⁄2 15.0 84Almonds 1 oz 15.0 80Sunflower seeds 1⁄4 cup 17.0 77Peanut butter 1 tbs 8.0 76Peanuts 1⁄4 cup 17.5 75Cashews 1 oz 13.2 73Egg 1 6.0 61Potato chips 1 oz (13 chips) 11.0 61Chocolate chip cookies 4 11.0 54French fries 20 fries 20.0 49Taco chips 1 oz (10 chips) 6.2 41

CandyMr. Goodbar 1.7 oz 15.0 56Peanut butter cups, 2 regular 1.6 oz 15.0 54Milk chocolate 1.6 oz 14.0 53Almond Joy 1.8 oz 14.0 50Kit Kat 1.5 oz 12.0 47M and M’s, peanut 1.7 oz 13.0 47Nestlé’s Crunch 1.6 oz 11.0 45Twix 2.0 oz 14.0 45Baby Ruth 2.1 oz 14.0 43Pay Day 1.9 oz 12.0 43Snickers 2.1 oz 13.0 42Butterfinger 2.1 oz 12.0 39M and M’s, plain 1.7 oz 10.0 39Milky Way 2.2 oz 11.0 353 Musketeers 2.1 oz 9.0 31Tootsie Roll 2.3 oz 6.0 21

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Reasons for the Revised Recommendations for Fat IntakeSeveral lines of evidence led to the recent changes in recommendations for fat intake.One line of evidence has taught us that although people tend to lose weight on low-fat diets, people also lose weight on high-fat, low- or high-carbohydrate, and low- orhigh-protein diets. Whether people lose weight and keep it off depends strongly onthe acceptability of the dietary changes made, and not on the relative proportions offat, carbohydrate, and protein content in the diet that lead to weight loss.31

Fat consumption among Americans decreased from 43% of total calories in1970 to around 33% of calories in recent years. Yet, the incidence of overweightand obesity in the United States has increased since 1970. Consequently, it is diffi-cult to argue that high fat diets are at the root of the obesity epidemic.32 As fatintake has decreased, carbohydrate intake has increased. Scientists are asking thequestion about whether high intakes of carbohydrate are related to rising rates ofobesity. Some evidence suggests that consumption of high-carbohydrate diets bypeople with low levels of physical activity and obesity may hasten the developmentof type 2 diabetes and other disorders related to insulin resistance.33

The experience of groups of people who have traditionally consumed high-fatdiets yet have average or below-average rates of heart and other chronic diseases hastaught us to view fat intake in the context of overall diet and lifestyle.34 A classicexample of the paradox between high-fat diets and low disease rates comes fromGreece and the traditional Mediterranean diet. This diet is based on whole grainproducts, vegetables, fruits, nuts, olive oil, dried beans, wine, fish, and poultry (Illus-tration 18.9). Over 40% of the calories in the diet come from fat, most of which isprovided in the form of monounsaturated fats. People consuming the traditionalMediterranean diet tend to be physically active and of normal weight or lean. Despitethis diet’s high fat content, populations consuming the diet and living the typicallifestyle have low rates of heart disease and cancer, and long life expectancy.35

A different example making the point that fat intake and health relationshipsshould be evaluated in the context of the overall diet and lifestyles come from Nige-ria. The Fulani pastoralists of Northern Nigeria subsist on a diet primarily com-posed of animal blood, meat, and dairy products. It is very high in fat and rich insaturated fat—yet the Fulani have normal levels of blood lipids and are not atincreased risk for heart disease. The Fulani are highly physically active, lean, andtend not to smoke.36

Rates of heart disease, cancer, type 2 diabetes, and obesity tend to increase in pop-ulations as they move from traditional diets and high levels of physical activity toWestern-type diets and sedentary lifestyles.37 In the new context, the relationship

TABLE 18.10

WHAT CLAIMS ABOUT THE CHOLESTEROL CONTENT OF FOODS THAT NORMALLY CONTAINCHOLESTEROL MUST MEAN.

• No cholesterol or cholesterol-free: Contains less than 3 milligrams of cholesterol per serving.

• Low cholesterol: Contains 20 milligrams or less of cholesterol per serving.

• Reduced cholesterol: Contains at least 75% less cholesterol than normal.

• Less cholesterol: Contains at least 25% less cholesterol than normal. The percentage lessmust be stated on the label.

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between fat intake and health changes—it becomessimilar to the situation in the United States andCanada. High-fat diets in these two countries areoften high in calories and saturated fat and low invegetables, fruits, and whole grain products. Gen-eral levels of physical activity in these countries tendto be low, and rates of obesity high. A high-fat,high-saturated fat diet under these circumstances isrelated to increased blood cholesterol levels and therisk of heart disease.38 New recommendations forfat intake take into consideration the effects onhealth of different sources and amounts of dietaryfat, and the potentially problematic influence oflow-fat diets on increasing carbohydrate intake inpopulations that tend to be inactive and obese. Rec-ommendations for fat intake are changing in partbecause of evidence pointing to the fact that sometypes of fat are better for health than others.

Good Fats, Bad FatsFats come in many types in foods, and with few exceptions, they serve as a sourceof energy and provide a number of essential functions in the body. With regard toraising or lowering the risk of heart disease and stroke, however, fats differ. Thosethat elevate total cholesterol and LDL-cholesterol levels are regarded as “bad” or“unhealthy” fats. Those that lower total cholesterol and LDL-cholesterol and raiseblood levels of HDL-cholesterol (the one that helps the body get rid of cholesterolin the blood) are considered “good” or healthy.”39

The list of unhealthy fats includes trans fats, saturated fats, and cholesterol. Fatslabeled bad are generally solid at room temperature and are included in foods such ashigh-fat meats and dairy products, hard margarines, shortening, and crispy snackfoods.40 Monounsaturated fats, polyunsaturated fats, alpha-linolenic acid, DHA, andEPA are considered healthy fats and are present in food in the form of oils (Table 18.11).

Illustration 18.9A look at the cuisine of theMediterranean diet.

REALITY CHECKGood fats, bad fatsGood fats, bad fats

What foods provide “healthy” fats

Who gets thumbs up

?Paprika: How can I be wrong?

Low-fat food products arebest for healthy fat

because they containalmost no fat!

Butch: I’m thinking foods likefish, peanut butter, andtrans fat-free margarine

contain healthy fats.

Answers on next page

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Recommendations for Fat and Cholesterol Intake

Current recommendations for adults call for consumption of 20–35% of total calo-ries from fat. The AIs (Adequate Intakes) for the essential fatty acid linoleic acid isset at 17 grams a day for men and 12 grams for women. AIs for the other essentialfatty acid, alpha-linolenic acid, are 1.6 grams per day for men and 1.1 grams forwomen. It is recommended that intake of trans fats and saturated fats be as low aspossible while consuming a nutritionally adequate diet. Only a small proportion ofAmericans consume too little linoleic acid, but intakes of alpha-linolenic acid tendto be low. Americans are being encouraged to increase consumption of EPA andDHA by eating fish more often. In addition, saturated fat intake averages 11–12%of calories, an amount that increases the risk of heart disease.41

There is no recommended level of cholesterol intake, because there is no evi-dence to indicate that cholesterol is required in the diet. The body is able to produceenough cholesterol, and people do not develop a cholesterol deficiency disease if it

TABLE 18.11

HEALTHY AND UNHEALTHY FATS AND EXAMPLES OF FOOD SOURCES.

HEALTHY FATS UNHEALTHY FATS

DHA, EPA (omega-3 fatty acids)fish and seafood

Monounsaturated fatsOlive and peanut oil, nuts, avocados

Polyunsaturated fatsVegetable oils

Alpha-linolenic acidSoybeans, walnuts, flaxseed

Trans fatsSnack and fried foods, bakery goods

Saturated fatsAnimal fats

Cholesteroleggs, seafood, and meat

ANSWERS TO REALITY CHECKGood fats, bad fatsGood fats, bad fats

Low-fat foods contain less fat than the regu-lar version of the foods. But that doesn’t

mean the products contain no fat, or onlygood fats. Food sources of fish oils, unsatu-

rated fat, and trans fat-free products providethe healthy fats. As always, healthy dietsaren’t based on individual foods, they arebased on overall diets. You can emphasize

foods providing healthy fats without feelingbad about occasionally eating foods branded

with the bad fat label.

�Paprika

�Butch

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is not consumed. Because blood cholesterol levels tend to increase somewhat as con-sumption of cholesterol increases, it is recommended that intake should be minimal.Although cholesterol intake averages around 250 mg per day in the United States, amore health-promoting level of intake would be less than 200 mg a day.42

Recent recommendations for fat intake represent an unusually large but neces-sary change in dietary intake guidance. The rationale for the changes has been devel-oping for years as research results emerged, showing consistent results thatsupported the new recommendations. Much remains to be understood about theeffects of dietary fats on health, and how other components of the diet and lifestyleand genetic traits modify relationships between fat intake and health. A beneficialby-product of the new recommendations for fat intake is that nutrient and healthrelationships are much more likely to be studied in the context of overall diets andlifestyles in the future.

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Key Termsessential fatty acids, page 18-3

hydrogenation, page 18-8

lipids, page 18-2 trans fats, page 18-9

Nutrition UP CLOSEThe Healthy Fats in Your Diet

FOCAL POINT: Identify your healthy fat food choices.

Are the fats in your diet thehealthy type? Check it out byanswering these questions:

How Often Do You Eat:

Seldom 1–2 Times 3–5 Times Almost or Never per Week per Week Daily

1. Sausage, hot dogs, ribs, and luncheon meats?

2. Heavily marbled steaks or roasts and chicken with the skin?

3. Soybean products such as tofu or soynuts?

4. Nuts or seeds?

5. Whole milk, cheese, or ice cream?

6. Soft margarine or olive oil?

7. French fries, snack crackers, commercial bakery products?

8. Rich sauces and gravies?

9. Fish or seafood?

10. Peanut butter?

FEEDBACK (including scoring) can be found at the end of Unit 18.

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Notes1. Dietary Reference Intakes, Energy, car-

bohydrate, fiber, fat, fatty acids, choles-terol, protein, and amino acids. Instituteof Medicine, National Academy of Sci-ences, Washington, DC: National Acad-emies Press; 2002; and Mensink RP etal., Effects of dietary fatty acids and car-bohydrates on the ratio of serum totalto HDL cholesterol and serum lipids,Am J Clin Nutr 2003;77:1146–55.

2. Dietary Reference Intakes.

3. Fat in your diet. How low should yougo? www.mayoclinic.com/invoke.cfm?id=HQ00670, accessed 6/03.


5. Fats: the good and the bad. www.mayoclinic.com/invoke.cfm?id=NU00262,accessed 9/03.

6. Connor WE. Importance of n-3 fattyacids in health and disease. Am J ClinNutr 2000;71(suppl):171S–5S.

7. Hepburn FN et al. Provisional tables onthe content of omega-3-fatty acids andother fat components of selected foods.J Am Diet Assoc 1986;86:788–93.

8. Everything you always wanted to knowabout those newfangled eggs. NutrToday 2003;38:75.


10. Vanschoonbeek K et al. Fish oil, con-sumption and reduction of arterial dis-ease. J Nutr 2003;133:657–60.

11. Krauss RM et al., Revision 2000: astatement for healthcare providers fromthe Nutrition Committee of the Ameri-can Heart Association, J Nutr 2001;131:132-46; and Kris-Etherton PM et al. New guidelines focus on fish, fishoil, omega-3 fatty acids. AHA State-ment. Circulation, 2002;Oct. 18.

12. Kris-Etherton, New guidelines.

13. Connor, Importance of n-3 fatty acids;and Hepburn et al., Provisional tables.


15. Stone NJ. Fish consumption, fish oil,lipids, and coronary heart disease. Am JClin Nutr 1997;65:1083–6.

16. Kris Etherton, New guidelines; andClarkson TW, Strain JJ, Nutrition fac-tors may modify the toxic action ofmethyl mercury in fish-eating popula-tions, J Nutr 2003;133:1539S-43S.



19. Krauss et al., Revision 2000.

20. Kris-Etherton PM et al. Polyunsaturatedfatty acids in the food chain in theUnited States. Am J Clin Nutr 2000;71(suppl):179S–88S.

21. Walsh J. Low fat, no fat, some fat . . .high fat? Envir Nutr 1998;21(April):1, 6.


23. Stuppy P, Transitioning away from transfatty acids, Today’s Dietitian 2003;Jan.:12–14; and Dietary Reference Intakes.


25. Vranico S. PepsiCo sets health-snackeffort. Wall Street Journal 2003, Sept.23, p. B6.

26. Sabar AF et al. Dietary sources of nutri-ents among U.S. adults. J Am Diet Assoc1998;98:537–47.

27. Gershoff SN, Nutrition evaluation ofdietary fat substitutes, Nutr Rev1995;53:305–13; and Mattes RD, Posi-tion of the American Dietetic Associa-tion: fat replacers, J Am Diet Assoc1998;98:463–8.

28. Mattes, Position of the ADA: fat replacers.

29. Bray GA et al. A 9-month randomizedcontrolled trial comparing fat-substitutedand fat-reduced diets in healthy obesemen: the Ole Study. Am J Clin Nutr2002;76:928–34.

30. Mattes, Position of the ADA: fat replac-ers; and Bray et al., A 9-month random-ized controlled trial.

31. Olson RE. Dietary fats: friend or foe?Nutr Notes, American Society of Nutri-tional Sciences, 2000;Mar.:3.

32. Olson, Dietary fats: friend or foe?

33. Dietary Reference Intakes; and SchwartzJ-M et al., Hepatic de novo lipogenesisin normoinsulinemic and hyperinsuline-mic subjects consuming high-fat, low-carbohydrate and low-fat, highcarbohydrate isoenergetic diets, Am JClin Nutr 2003;77:43–50.


35. Trichopoulou A et al. Adherence to aMediterranean diet and survival in aGreek population. N Engl J Med2003;348:2599–608.

36. Glew RH et al. Cardiovascular diseaserisk factors and diet of the Fulani pas-toralists of Northern Nigeria. Am J ClinNutr 2001;74:730–6.

37. Hu FB. The Mediterranean diet andmortality—olive oil and beyond. N EnglJ Med 2003;348:2595–6.

38. Dietary Reference Intakes; and Krauss etal., Revision 2000.

39. Fats: the good and the bad (www.mayoclinic.com/invoke.cfm?id=NU00262); and Kris-Etherton et al.,New guidelines.

40. Fats: the good and the bad (www.mayoclinic.com/invoke.cfm?id=NU00262).



www linkswww.nlm.nih.gov/medlineplus/dietaryfat.htmlProvides a menu that connects you to sitessuch as good and bad fats, interpretingblood lipid profiles, benefits of flaxseed,and fat substitutes.

www.nal.usda.gov/fnicFind out more about fats and fat substi-tutes from the extensive list of topics cov-ered under the search term “fats.”

www.healthfinder.govGood source of information on fats, transfat, and cholesterol through search termssuch as dietary fat and healthy fats.

www.mayoclinic.orgHealthy fats, bad fats, know your fats, fatsand heart disease, and other topics areintelligently covered in sites availablethrough the Mayo Clinic’s home page.

www.epa.gov/ost/fishThe Environmental Protection Agency’s sitefor looking up national and local advisorieson fish contamination and consumption.

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Nutrition UP CLOSEThe Healthy Fats in Your Diet

Feedback for Unit 18Give yourself a point for each time you checked the “3-5 Times per Week” or “Almost Daily”columns for numbers 3, 4, 6, 9, and 10. These foods are sources of healthy unsaturated fats orDHA and EPA. Take a point away for each time your answer ended up in the same columns forfoods listed in numbers 1, 2, 5, 7, and 8. These foods provide saturated or trans fats. If you haveany points left, your selection of food sources of fat regularly include healthy fats.

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fats and - cengage...fatty acid families of omega-6 (also called n-6 fatty acids) and omega-3 fatty...

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