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US E TRUE Nutrition Scoreboard FALSE RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O OM Fats and Cholesterol in Health 1 It is currently recommended that adults consume diets providing less than 30% of calories from fat. 3 Cholesterol is present in every food. FO R 4 Saturated fat intake has a much stronger influence on blood cholesterol levels than does cholesterol intake. Answers on next page 2 The types of fat consumed are more important to health than is total fat intake. • Fats are our most concen- trated source of food energy. They supply 9 calories per gram. • Dietary fats “carry” the essential fatty acids, fatsoluble vitamins, and healthful phytochemicals along with them in foods. • Fats are not created equal. Some types of fat have posi- tive effects, and some have negative effects on health. • Saturated fats and trans fats raise blood cholesterol levels more than does dietary cholesterol or any other type of fat. TRUE Answers to Nutrition Scoreboard ] ✔ 1 Recommendations for fat intake have changed! The acceptable range of fat intake is now 20-35% of total calories. 2 The types of fat consumed are more important to health than the total amount of fat.1 ✔ ✔ 3 Cholesterol is present only in animal products. 4 Saturated fat, which is found primarily in animal products, raises blood cholesterol levels a good deal more than does dietary cholesterol. FALSE US E OM KEY CONCEPTS AND FACTS RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O [ ✔ Changing Views about Fat Intake and Health Scientific evidence and opinions related to the effects of fat on health have changed substantially in recent years—and so have recommendations about fat intake. In the past, it was recommended that Americans aim for diets providing less than 30% of total calories from fat. Evidence indicating that the type of fat consumed is more important to health than is total fat intake has changed this advice. The watchwords for thinking about fat have become “not all fats are created equal: some are better for 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% of total caloric intake. Concerns that high-fat diets encourage the development of obesity have been eased by studies demonstrating that excessive caloric intakes—and not just diets high in fat—are related to weight gain.2 New recommendations regarding fat intake do not encourage increased fat consumption. Rather, they emphasize that healthy diets include certain types of fat, and that total caloric intake and physical activity are the most important components of weight management. Diets providing as low as 20% of calories from fat, and those providing 30–35%, can be healthy—depending on the types of fat consumed and the quality of the rest of the diet.3 This unit provides facts about fats, explains the reasons behind recent changes in recommendations for fat intake, and addresses the practical meaning of it all. Facts about Fats FO R lipids Compounds that are insoluble in water and soluble in fat. Triglycerides, saturated and unsaturated fats, and essential fatty acids are examples of lipids, or “fats.” Fats are a group of substances found in food. They have one major property in common: they are not soluble (or, in other words, will not dissolve) in water. If you have ever tried to mix vinegar and oil when making salad dressing, you have observed the principle 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, and shortening are often distinguished from oils by their property of being solid at room US E ROLES OF DIETARY FAT. • Provides a concentrated source of energy • Carries the essential fatty acids, the fatsoluble vitamins, and certain phytochemicals RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Contributions of Dietary Fats TABLE 18.1 OM temperature. This physical difference between fats and oils is due to their chemical structures. Fats in Foods Supply Energy and Fat-Soluble Nutrients] Fats include the essential fatty acids (linoleic acid and alpha-linolenic acid) and provide the fatsoluble vitamins D, E, K, and A (the “deka” vitamins). So, part of the reason we need fats in our diet is to get a supply of the essential nutrients they contain (Table 18.1). Diets containing little fat (less than 20% of total calories) often fall short on delivering adequate amounts of essential fatty acids and fat-soluble vitamins.4 Fats Increase the Flavor and Palatability of Foods] Although “pure” fats by • Increases the flavor and palatability of foods • Provides sustained relief from hunger themselves tend to be tasteless, they absorb and retain the flavor of substances that surround them. Thus, fats in meats and other foods pick up flavors from their environment 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. • Serves as a component of cell membranes Fats Contribute to the Sensation of Feeling Full] As they should, at 9 calo- essential fatty acids Components of fats (linoleic acid—pronounced lynn-oh-layick and alpha-linolenic acid— lynn-oh-len-ick) required in the diet. ries per gram! Fats tend to stay in the stomach longer than carbohydrates or proteins and are absorbed over a longer period of time. That’s why foods with fat “stick to 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 of nutrients into and out of cells.6 Excess Dietary Fat, Carbohydrates, and Protein Are Stored as Fat Fats in the body include those consumed in the diet and those produced from carbohydrates and proteins. Humans eat only a few times a day, but we need energy throughout the day. To ensure a constant supply of energy, the body converts carbohydrates and proteins, which have been supplied from foods and are not used to meet immediate needs, to storage forms of energy. Some of the excess carbohydrate and protein is converted to glycogen, the storage form of glucose under normal circumstances, but most of the excess is changed to fat and stored in fat cells (Illustration 18.1). Body fat is not just skin deep. Fat is also located around organs such as the kidneys 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 insulation (Illustration 18.2). FO R Fats Come in Many Varieties There are many types of fat in food and our bodies (Table 18.2). Of primary importance are triglycerides (or “triacylglycerols”), saturated and unsaturated fats, and cholesterol (for definitions, see Table 18.3). The different types of fats have different effects on health. US E OM AP Photo RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Biophoto/Photo Researchers Triglycerides, which consist of one glycerol unit (a glucose-like substance) and three fatty acids (Illustration 18.3), make up 98% of our dietary fat intake and the vast majority of our body’s fat stores. Triglycerides are transported in blood attached to protein carriers and are used by cells for energy formation and tissue maintenance. A minority of fats take the form of diglycerides (glycerol plus two fatty acids) and monoglycerides (glycerol and one fatty acid). Diglycerides are present in some oils and small amounts are used in food products as emulsifiers—or to increase the blending of fat- and water-soluble substances. Monoglycerides are present in small amounts in some oils; we don’t consume very much of them in foods. As far as health is concerned, the glycerol component of fat is relatively unimportant. It’s the fatty acids that influence what the body does with the fat we eat; and they are responsible, in part, for how fat affects health. Many different types of fatty acids are found in triglycerides. You’ve heard of the major ones: those that make fat “saturated” or “unsaturated.” Illustration 18.1 A close look at fat cells (color-enhanced microphotograph). Illustration 18.2 Although their body fat stores don’t fit the image of the superathlete, coldwater swimmers need the fat to help stay warm. Pictured here is the English swimmer Mike Read, who had swum the English Channel 20 times by age 39. Saturated and Unsaturated Fats] Fatty acids found in fats consist primarily of TABLE 18.2 BASIC FACTS ABOUT THE TYPES OF FAT. Fats can be: • Monoglycerides • Diglycerides • Triglycerides Fats can be: • Saturated R • Monounsaturated FO • Polyunsaturated Unsaturated fats come in: • “Cis” forms • “Trans” forms hydrogen atoms attached to carbon atoms (Illustration 18.4). When the carbons are attached 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 the maximum are “unsaturated.” They tend to be liquid at room temperature. By and large, 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 “monounsaturated.” If two or more carbon-carbon bonds are unsaturated with hydrogen, the fat qualifies as “polyunsaturated.” The Omega-3 and Omega-6 Fatty Acids The essential fatty acids linoleic acid and alpha-linolenic acid are members of the fatty 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 used as a source of energy, and are stored in fat tissue. Because they are essential, both linoleic and alpha-linolenic acid are required in the diet. Linoleic acid is required for growth, maintenance of healthy skin, and normal functioning of the reproductive system. It is a component of all cell membranes and is found in particularly high amounts in nerves and the brain. A number of biologically active compounds, produced in the body, that participate in regulation of blood pressure and blood clotting are derived from linoleic acid. The major food sources of linoleic acid are sunflower, safflower, corn, and soybean oils. US E TABLE 18.3 Glycerol + 3 fatty acids = Triglyceride + + RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Triglycerides: Fats in which the glycerol molecule has three fatty acids attached to it; also called triacylglycerol. Triglycerides are the most common type of fat in foods and in body fat stores. OM Illustration 18.3 A triglyceride. A GLOSSARY OF FATS. Saturated fats: Molecules of fat in which adjacent carbons within fatty acids are linked only by single bonds. The carbons are “saturated” with hydrogens; that is, they are attached to the maximum possible number of hydrogens. Saturated fats tend to be solid at room temperature. 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 more double bonds. The carbons are not saturated with hydrogens; that is, they are attached to fewer than the maximum possible number of hydrogens. Unsaturated fats tend to be liquid at 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 to glucose in chemical structure. Cholesterol: A fat-soluble, colorless liquid found in animals but not in plants. Cholesterol is used by the body to form hormones such as testosterone and estrogen and is a component of animal cell membranes. Diglyceride: A fat in which the glycerol molecule has two fatty acids attached to it; also called diacylglycerol. Monoglyceride: A fat in which the glycerol molecule has one fatty acid attached to it; also called monoacylglycerol. Monounsaturated fats: Fats that contain a fatty acid in which one carbon-carbon bond is not saturated with hydrogen. Polyunsaturated fats: Fats that contain a fatty acid in which two or more carbon-carbon bonds are not saturated with hydrogen. Hydrogen Oxygen CH3 Oxygen Carbon Saturated fatty acid CH CH Monounsaturated fatty acid CH CH CH CH FO R Polyunsaturated fatty acid 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. Illustration 18.4 A look at the difference between a saturated and an unsaturated fatty acid. Illustration 18.5 Fat profiles of selected foods. US E Monounsaturated Saturated Polyunsaturated OM PERCENTAGE FATTY ACID COMPOSITION DAIRY PRODUCTS Brick cheese Cheddar cheese Cottage cheese American cheese Whole milk Butter 30 3 67 30 3 67 30 3 RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O 67 65 48 EGG (medium) 4 31 31 65 HUMAN MILK 3 30 67 4 12 40 37 48 15 OILS AND MARGARINES 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 13 6 2 62 25 61 17 18 9 22 73 14 9 77 52 38 10 48 18 22 28 50 21 11 34 60 25 15 68 MEATS Hamburger (21% fat) 53 Chicken, roasted (no skin) Pork chop Turkey, roasted 26 46 39 43 4 28 49 40 25 12 35 NUTS AND SEEDS 62 21 46 16 52 15 18 11 51 20 17 2 33 32 69 FO R Photo Disc Cashews Macadamia Nuts Peanuts, dry-roasted Peanut butter Sunflower seeds (dried) Alpha-linolenic acid, EPA (eicosapentaenoic acid—pronounced e-co-sah-penttah-no-ick) and DHA (docosahexaenoic acid: dough-cos-ah-hex-ah-no-ick) are primary members of the omega-3 fatty acid family. Alpha-linolenic acid is an essential nutrient, but EPA and DHA are not. These two members of the omega-3 fatty acid family can be produced in the body from alpha-linolenic acid. However, the con- US E —Penny Kris-Etherton, Distinguished Professor of Nutrition12 Eric Risberg/AP Photo Omega-3 fatty acids are not just good fats, they affect heart health in positive ways. The Omega-3 Fatty Acids and Fish Oils] Many unsaturated fats contain fatty acids with one or two unsaturated carbon-to-carbon bonds. DHA and EPA found in fish oils, however, stand out in that they contain from 4 to 6 double bonds. This high level of unsaturation gives these omega-3 fatty acids the unique property of being highly fluid even at cold temperatures. This property allows the fatty acids to keep cell membranes and fat-containing tissues in fish flexible in cold water. Fatty fish and fish that live in cold water contain the highest amounts of DHA and EPA (Table 18.4). In humans, DHA and EPA form biologically active compounds that reduce blood pressure and the tendency of blood to clot, and these properties confer health advantages. Regular consumption of these omega-3 fatty acids (two or more fishcontaining meals per week) decreases the risk of heart attack, protects against irregular heartbeat and sudden death, decreases plaque formation in arteries, lowers high blood pressure, and decreases the risk of stroke. Fish oil capsules are being increasingly viewed as potential sources of EPA and DHA. They are sometimes recommended for people at risk of heart disease and should be taken under medical supervision. High levels of fish oils (over 3 grams per day) can prevent blood from clotting.14 FO R Mercury in Fish and Fish Intake} Some fish contain high levels of mercury that can end up in fish oil supplements.15 Mercury was found to be a potent fungicide over 100 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 many decades. Several catastrophic outbreaks of mercury poisoning due to consumption of contaminated fish occurred during the mid-1900s and brought a halt to the use of mercury fungicides. Mercury is still found in some ocean and lake fish, but recent studies indicate that the benefits of fish intake among people over the age of 40 far outweigh risks related to mercury.16 Pregnant and breastfeeding women, and infants, are particularly susceptible to the harmful effects of mercury and are advised to omit from their diets the top four mercury-rich fish: shark, swordfish, king mackerel, and tilefish (also called golden snapper and golden bass). Intake of all other fish should be limited to 12 ounces or less per week among pregnant and breastfeeding women, and to 2 ounces or less for children under the age of 6 years.17 Local advisories related to mercury levels of fish in lakes and streams are available online (www.epa.gov/ost/fish), and advice on intake levels of fish caught in ON THE SIDE RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O OM version of this essential fatty acid to EPA and DHA is slow and results in the availability of relatively little EPA and DHA.9 Alpha-linolenic acid is a structural component of all cell membranes and is found in high amounts in cells of the brain and eyes. Alpha-linolenic acid is also involved in the formation of biologically active compounds used in regulating blood pressure and blood clotting; but these compounds have the opposite effect on the blood pressure and blood clotting, as do linoleic acid derivatives.10 Omega 3-fatty Fishy eggs? An odd source of fish oil acids are found in a few foods such as walnuts, flaxseed, canola oil, and has become part of North Americans’ soybeans in the form of alpha-linolenic acid. The most beneficial sources diets. Hens given feed with added cod of omega-3 fatty acids, however, are marine oils—due to their content liver oil produce eggs with yolks conof DHA and EPA.11 These two omega-3 fatty acids play important taining 100 to 350 milligrams of highly roles in disease prevention and health promotion. unsaturated omega-3 fatty acids.8 OMEGA-3 FATTY ACIDS (GRAMS) SEAFOOD (31⁄2-OUNCE SERVING RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O SEAFOOD (31⁄2-OUNCE SERVING) OM OMEGA-3 FATTY ACID (EPA & DHA) CONTENT OF SELECTED SEAFOODS.13 Sardines in sardine oil Mackerel Salmon, Atlantic, farmed Lake trout Herring Salmon, Atlantic, wild Tuna, white, canned Salmon, sockeye Whitefish, lake Anchovies Salmon, chinook Bluefish Halibut Trout, rainbow, farmed Oysters Salmon, pink Trout, rainbow, wild Bass, striped Swordfish 3.3 2.6 2.2 2.0 1.8 1.8 1.7 1.5 1.5 1.4 1.4 1.2 1.2 1.2 1.1 1.0 1.0 0.8 0.8 Oysters Catfish Flounder Shrimp Halibut Pollock Scallops Whiting Carp Crab Pike, walleye Tuna, fresh Catfish, wild Clams Fish sticks Haddock Lobster Salmon, red Snapper, red US E TABLE 18.4 OMEGA-3 FATTY ACIDS (GRAMS) 0.6 0.5 0.2 0.5 0.5 0.5 0.5 0.5 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.2 them should be heeded. Large fish (longer than 20 inches) in general contain higher concentrations of mercury than do smaller fish, so you may want to let the big ones get 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 mercury.18 Other sources of DHA and EPA include eggs enriched with omega-3 fatty acids. The American Heart Association recommends that adults consume two or more 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 of omega-6 to omega-3 fatty acid intake is important because the functions of one are adversely 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 should consume 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 infrequently. Consequently, the ratio between the intake of omega-6 and omega-3 fatty acids is over 9 to 1, indicating a need to increase intake of omega-3 fatty acids.20 FO R Modifying Fats hydrogenation The addition of hydrogen to unsaturated fatty acids. Unsaturated fats aren’t as stable as saturated fats. They are more likely to turn rancid 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 with unsaturated fats have a solution. It’s called hydrogenation. What’s Hydrogenation?] Hydrogenation is a process that adds hydrogen to liquid unsaturated fats, thereby making them more saturated and solid. The shelf life, cooking properties, and taste of vegetable oils are improved in the process. Hydrogenation has two drawbacks, however. Hydrogenated vegetable oils contain more US E OM trans fats Unsaturated fatty acids in fats that contain atoms of hydrogen attached to opposite sides of carbons joined by a double bond: RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O saturated fat than the original oil. Corn oil, for example, contains only 6% saturated fats; but corn oil margarine has 17%. The other negative is that hydrogenation 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 may be converted from their naturally occurring “cis” to the “trans” form as a result of hydrogenation.21 Fatty acids in this structural form raise blood cholesterol levels more than dietary cholesterol, saturated fats or any other type of fat do.22 The bulk of trans fat in our diet comes from hydrogenated vegetable oils. Trans fats are more stable and have a longer shelf life than other fats and are preferred for use in margarine, snack foods, bakery products, and fried foods (Table 18.5). Ruminant animals 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 States consume 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 and new nutrition information labeling requirements are making that easier to accomplish. Nutrition Facts panels must include the trans fat content of food products by January 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. Products labeled “trans fat–free” must contain less than 0.5 gram of both trans and saturated fats. It is expected that the requirement to label the trans fat content of food products will increase the number of foods labeled “trans fat–free” and “no trans fat” (Illustration 18.7) and decrease its use in foods. Food companies are busy developing other ways to produce foods without them.25 H –CC H H H –CC– Cis fatty acid Trans fatty acid Fats containing fatty acids in the trans form are generally referred to as trans fats. Cis fatty acids are the most common, naturally occurring form of unsaturated fatty acids. They contain hydrogens located on the same side of doubly bonded carbons. Checking Out Cholesterol Cholesterol is a lipid found only in animal products. It is tasteless and odorless and contained in both the lean and fat parts of animal products. Table 18.6 lists some sources of cholesterol. Plants don’t contain cholesterol because they can’t produce it and don’t need it to function and grow normally. Sources of Cholesterol 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 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 The Contributions of Cholesterol Snack crackers,1 2 oz 2 Shortening, 1 tbs 1 Would you be surprised to learn that cholesterol: Tub margarine, 1 tbs 1 • is found in every cell in your body? Butter, 1 tbs 0 • serves as the building block for estrogen, “No trans fat” margarine 0 Olive oil 0 FO R French fries, large serving The cholesterol used by the body comes from two sources. Most (about two-thirds) of the cholesterol available to the body is produced by the liver. The rest comes from the diet (Illustration 18.8). Because the liver produces cholesterol from other substances in our diet, it does not qualify as an essential nutrient. testosterone, and the vitamin D that is produced in your skin upon exposure to sunlight? Nutrition Facts Serving Size 1 Entree Serving Per Container 1 Amount Per Serving Calories 380 Calories from Fat 170 %Daily Value Total Fat 19g 29% 50% Saturated Fat 10g Trans Fat 2g Cholesterol 85g 28% 34% Sodium 810mg Total Carbohydrate 33g 11% 12% Dietary Fiber 3g Sugars 5g Protein 20g Vitamin A 10% Calcium 10% Vitamin C 0% 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: Calories Less Than Total Fat Less Than Sat Fat Cholesterol Less Than Less Than Sodium Total Carbohydrate Dietary Fiber 2000 2500 65g 20g 300mg 2400mg 300g 25g 80g 25g 300mg 2400mg 375g 30g FO R Illustration 18.7 Products that feature “no trans fats” and “trans fat–free” labels. Richard Anderson • cannot be used for energy (so it provides no calories)? US E OM • is a major component of nerves and the brain? The body has many uses for cholesterol (Table 18.7). It doesn’t just accumulate in arteries! RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Illustration 18.6 Trans fat: the newest addition to Nutrition Facts panels. Fat Substitutes The fat content of processed foods can be partially or fully replaced by fat substitutes. Fat substitutes attempt to imitate the taste, texture, and cooking properties of our favorite fats, but with fewer calories. Table 18.8 lists some of the more than 60 products that are already on the market; others are under development. The degree to which these products succeed in imitating the qualities of fat varies. Making the TABLE 18.6 FOOD SOURCES OF CHOLESTEROL. Note that all the sources are animal products. Cholesterol in foods is a clear, oily liquid found in the fat and lean portions of many animal products. 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 ANIMAL PRODUCT 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 US E TABLE 18.7 perfect fat substitute is not an easy task. Not all of the fat substitutes that have entered the marketplace have met the test of consumer acceptability.28 OM HOW THE BODY USES CHOLESTEROL. Are Fat Substitutes Safe? RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O • Cholesterol is a component of all cell membranes, the brain, and nerves. Consumers sometimes wonder about the safety of fat substitutes. Because most fat substitutes are derived from ingredients of food such as carbohydrates, protein, and vegetable oils, they are often assumed to be safe. Fat replacers that are made from substances that do not occur naturally in foods must be tested for safety. Olean, a non-naturally occurring fat replacer that cannot be digested, was tested extensively before being approved for use. It can cause diarrhea and oily stools if consumed in large amounts.29 When substituted for foods containing saturated fats, fat substitutes may benefit health by lowering blood cholesterol levels. Studies suggest that the use of foods containing fat substitutes reduces total fat consumption, but whether they lead to weight loss is controversial. So, although they may not be the answer to weight control, fat substitutes may provide part of the solution to high fat intakes and the health problems related to them.30 Finding Out about the Fat Content of Food Other foods 15% Fats 5% Not all of the fat in food is visible. To avoid being fooled, it helps to use a reference on the fat composition of foods. Table 18.9 lists the fat content of common food sources of fat, including candy. Vegetables and fruits (except avocado and coconut) and grains are not listed because they contain relatively little fat. Other references can also be used, such as the food composition tables in Appendix A, the Diet Analysis Plus Program software, and the nutrition labels on food products. Milk and milk products 15% Meats 36% TABLE 18.8 SOME FAT SUBSTITUTES.27 CARBOHYDRATE-BASED (0–4 CAL/G) FO R Amalean I and II CrystaLean Instant Stellar Juguar Litesse Maltrin N-Lite Oat fiber Oatrim Opta Grade Pure-gel Sta-Slim Sta-Lite PROTEIN-BASED (1–2 CAL/G) K-Blazer Proplus Simplesse FAT-BASED (0–5 CAL/G) Benefat Caprenin Olean Illustration 18.8 Food sources of cholesterol in the U.S. diet.26 Percentages indicate the proportion of cholesterol each type of food contributes to the diet. COMBINATIONS Fitesse Nutrifat Prolestra Photo Disc Can Fat Substitutes Benefit Health? • It is needed to produce estrogen, testosterone, and vitamin D. Eggs (egg yolk) 29% US E RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O OM Knowledge of the caloric and fat content of a food can be used to calculate the percentage of calories provided by fat. For example, suppose that a slice of cherry pie provides 350 calories and 15 grams of fat. To calculate the percentage of fat calories, multiply 15 grams by 9 (the number of calories in each gram of fat), divide the result by 350 calories, and then multiply by 100: 15 grams fat 9 calories/gram 135 calories 135 calories/350 0.39 0.39 100 39% of total calories from fat Fat Labeling Nutrition labeling regulations for fat require food manufacturers to adhere to standard definitions of “low fat,” “fat-free,” and related terms used on food labels. Similarly, claims made about the cholesterol content of food products must comply with standard definitions (Table 18.10, on page 18-14). If a claim is made about the fat content of a food, the Nutrition Facts panel must specify the food’s fat, saturated fat, 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), the nutrition panel must also reveal the product’s fat and saturated fat content. To prevent the use of unrealistically small serving sizes as a way to appear to cut down on a product’s fat content, standard serving sizes must be used on food labels. TABLE 18.9 THE FAT CONTENT OF SOME FOODS. FO R FOOD Fats and oils Butter Margarine Oil Mayonnaise Heavy cream Salad dressing Meats and fast foods Hot dog Bologna Sausage Bacon Salami Pork steak Hamburger, regular (20% fat) Chicken, fried with skin Big Mac Quarter Pounder with cheese Whopper Steak (rib eye) Hamburger, lean (10% fat) Steak (T-bone), lean Rabbit Veggie pita Ranch chicken pita AMOUNT GRAMS PERCENTAGE OF TOTAL CALORIES FROM FAT 1 tsp 1 tsp 1 tsp 1 tbs 1 tbs 1 tbs 4.0 4.0 4.7 11.0 5.5 6.0 100% 100 100 99 93 83 1 (2 oz) 1 oz 4 links 3 pieces 2 oz 3 oz 3 oz 3 oz 6.6 oz 6.8 oz 8.9 oz 3 oz 3 oz 3 oz 3 oz 1 1 17.0 8.0 18.0 9.0 11.0 18.0 16.5 14.0 31.4 28.6 32.0 9.9 9.5 8.9 7.0 17.0 18.0 83 80 77 74 68 62 62 53 52 50 48 47 45 44 38 38 34 US E THE FAT CONTENT OF SOME FOODS. (CONTINUED) AMOUNT GRAMS PERCENTAGE OF TOTAL CALORIES FROM FAT RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O FOOD OM TABLE 18.9 FO R Meats and fast foods—continued Steak (round), lean only 3 oz 5.2 Chicken, baked without skin 3 oz 4.0 Turkey wrap 1 9.0 Hamburger, extra lean (4% fat) 3 oz 2.3 Venison 3 oz 2.7 Subway, club 6" 5.0 Flounder, baked 3 oz 1.0 Subway, veggie 6" 3.0 Shrimp, boiled 3 oz 1.0 Milk and milk products Cheddar cheese 1 oz 9.5 American cheese 1 oz 6.0 Milk, whole 1 cup 8.5 1 Cottage cheese, regular ⁄2 cup 5.1 Milk, 2% 1 cup 5.0 Milk, 1% 1 cup 2.7 1 Cottage cheese, 1% fat ⁄2 cup 1.2 Milk, skim 1 cup 0.4 3 Yogurt, frozen ⁄4 cup 0.0–6.6 Other Olives 4 medium 1.5 1 Avocado ⁄2 15.0 Almonds 1 oz 15.0 1 Sunflower seeds ⁄4 cup 17.0 Peanut butter 1 tbs 8.0 1 Peanuts ⁄4 cup 17.5 Cashews 1 oz 13.2 Egg 1 6.0 Potato chips 1 oz (13 chips) 11.0 Chocolate chip cookies 4 11.0 French fries 20 fries 20.0 Taco chips 1 oz (10 chips) 6.2 Candy Mr. Goodbar 1.7 oz 15.0 Peanut butter cups, 2 regular 1.6 oz 15.0 Milk chocolate 1.6 oz 14.0 Almond Joy 1.8 oz 14.0 Kit Kat 1.5 oz 12.0 M and M’s, peanut 1.7 oz 13.0 Nestlé’s Crunch 1.6 oz 11.0 Twix 2.0 oz 14.0 Baby Ruth 2.1 oz 14.0 Pay Day 1.9 oz 12.0 Snickers 2.1 oz 13.0 Butterfinger 2.1 oz 12.0 M and M’s, plain 1.7 oz 10.0 Milky Way 2.2 oz 11.0 3 Musketeers 2.1 oz 9.0 Tootsie Roll 2.3 oz 6.0 29 25 24 23 18 14 13 11 10 74 66 49 39 32 24 13 4 0–3 90 84 80 77 76 75 73 61 61 54 49 41 56 54 53 50 47 47 45 45 43 43 42 39 39 35 31 21 US E TABLE 18.10 OM WHAT CLAIMS ABOUT THE CHOLESTEROL CONTENT OF FOODS THAT NORMALLY CONTAIN CHOLESTEROL MUST MEAN. RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O • 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 less must be stated on the label. FO R Reasons for the Revised Recommendations for Fat Intake Several 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 lowfat diets, people also lose weight on high-fat, low- or high-carbohydrate, and low- or high-protein diets. Whether people lose weight and keep it off depends strongly on the acceptability of the dietary changes made, and not on the relative proportions of fat, carbohydrate, and protein content in the diet that lead to weight loss.31 Fat consumption among Americans decreased from 43% of total calories in 1970 to around 33% of calories in recent years. Yet, the incidence of overweight and obesity in the United States has increased since 1970. Consequently, it is difficult to argue that high fat diets are at the root of the obesity epidemic.32 As fat intake has decreased, carbohydrate intake has increased. Scientists are asking the question about whether high intakes of carbohydrate are related to rising rates of obesity. Some evidence suggests that consumption of high-carbohydrate diets by people with low levels of physical activity and obesity may hasten the development of type 2 diabetes and other disorders related to insulin resistance.33 The experience of groups of people who have traditionally consumed high-fat diets yet have average or below-average rates of heart and other chronic diseases has taught us to view fat intake in the context of overall diet and lifestyle.34 A classic example of the paradox between high-fat diets and low disease rates comes from Greece and the traditional Mediterranean diet. This diet is based on whole grain products, vegetables, fruits, nuts, olive oil, dried beans, wine, fish, and poultry (Illustration 18.9). Over 40% of the calories in the diet come from fat, most of which is provided in the form of monounsaturated fats. People consuming the traditional Mediterranean diet tend to be physically active and of normal weight or lean. Despite this diet’s high fat content, populations consuming the diet and living the typical lifestyle have low rates of heart disease and cancer, and long life expectancy.35 A different example making the point that fat intake and health relationships should be evaluated in the context of the overall diet and lifestyles come from Nigeria. The Fulani pastoralists of Northern Nigeria subsist on a diet primarily composed of animal blood, meat, and dairy products. It is very high in fat and rich in saturated fat—yet the Fulani have normal levels of blood lipids and are not at increased risk for heart disease. The Fulani are highly physically active, lean, and tend not to smoke.36 Rates of heart disease, cancer, type 2 diabetes, and obesity tend to increase in populations as they move from traditional diets and high levels of physical activity to Western-type diets and sedentary lifestyles.37 In the new context, the relationship US E OM Photo Disc RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Good Fats, Bad Fats Fats come in many types in foods, and with few exceptions, they serve as a source of energy and provide a number of essential functions in the body. With regard to raising or lowering the risk of heart disease and stroke, however, fats differ. Those that elevate total cholesterol and LDL-cholesterol levels are regarded as “bad” or “unhealthy” fats. Those that lower total cholesterol and LDL-cholesterol and raise blood levels of HDL-cholesterol (the one that helps the body get rid of cholesterol in the blood) are considered “good” or healthy.”39 The list of unhealthy fats includes trans fats, saturated fats, and cholesterol. Fats labeled bad are generally solid at room temperature and are included in foods such as high-fat meats and dairy products, hard margarines, shortening, and crispy snack foods.40 Monounsaturated fats, polyunsaturated fats, alpha-linolenic acid, DHA, and EPA are considered healthy fats and are present in food in the form of oils (Table 18.11). Illustration 18.9 A look at the cuisine of the Mediterranean diet. REALITY CHECK Good fats, bad fats Good fats, bad fats What foods provide “healthy” fats Who gets thumbs up ? FO R Paprika: How can I be wrong? Low-fat food products are best for healthy fat because they contain almost no fat! Answers on next page Butch: I’m thinking foods like fish, peanut butter, and trans fat-free margarine contain healthy fats. Photo Disc between fat intake and health changes—it becomes similar to the situation in the United States and Canada. High-fat diets in these two countries are often high in calories and saturated fat and low in vegetables, fruits, and whole grain products. General levels of physical activity in these countries tend to be low, and rates of obesity high. A high-fat, high-saturated fat diet under these circumstances is related to increased blood cholesterol levels and the risk of heart disease.38 New recommendations for fat intake take into consideration the effects on health of different sources and amounts of dietary fat, and the potentially problematic influence of low-fat diets on increasing carbohydrate intake in populations that tend to be inactive and obese. Recommendations for fat intake are changing in part because of evidence pointing to the fact that some types of fat are better for health than others. US E REALITY CHECK Low-fat foods contain less fat than the regular version of the foods. But that doesn’t mean the products contain no fat, or only good fats. Food sources of fish oils, unsaturated fat, and trans fat-free products provide the healthy fats. As always, healthy diets aren’t based on individual foods, they are based on overall diets. You can emphasize foods providing healthy fats without feeling bad about occasionally eating foods branded with the bad fat label. RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O Photo Disc Good fats, bad fats Good fats, bad fats OM ANSWERS TO Paprika Butch Recommendations for Fat and Cholesterol Intake Current recommendations for adults call for consumption of 20–35% of total calories from fat. The AIs (Adequate Intakes) for the essential fatty acid linoleic acid is set at 17 grams a day for men and 12 grams for women. AIs for the other essential fatty acid, alpha-linolenic acid, are 1.6 grams per day for men and 1.1 grams for women. It is recommended that intake of trans fats and saturated fats be as low as possible while consuming a nutritionally adequate diet. Only a small proportion of Americans consume too little linoleic acid, but intakes of alpha-linolenic acid tend to be low. Americans are being encouraged to increase consumption of EPA and DHA 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 evidence to indicate that cholesterol is required in the diet. The body is able to produce enough cholesterol, and people do not develop a cholesterol deficiency disease if it TABLE 18.11 HEALTHY AND UNHEALTHY FATS AND EXAMPLES OF FOOD SOURCES. FO R HEALTHY FATS UNHEALTHY FATS DHA, EPA (omega-3 fatty acids) fish and seafood Trans fats Snack and fried foods, bakery goods Monounsaturated fats Olive and peanut oil, nuts, avocados Saturated fats Animal fats Polyunsaturated fats Vegetable oils Cholesterol eggs, seafood, and meat Alpha-linolenic acid Soybeans, walnuts, flaxseed FO R US E OM RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O is not consumed. Because blood cholesterol levels tend to increase somewhat as consumption of cholesterol increases, it is recommended that intake should be minimal. Although cholesterol intake averages around 250 mg per day in the United States, a more health-promoting level of intake would be less than 200 mg a day.42 Recent recommendations for fat intake represent an unusually large but necessary change in dietary intake guidance. The rationale for the changes has been developing for years as research results emerged, showing consistent results that supported the new recommendations. Much remains to be understood about the effects of dietary fats on health, and how other components of the diet and lifestyle and genetic traits modify relationships between fat intake and health. A beneficial by-product of the new recommendations for fat intake is that nutrient and health relationships are much more likely to be studied in the context of overall diets and lifestyles in the future. US E UP CLOSE OM Nutrition RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O The Healthy Fats in Your Diet FOCAL POINT: Identify your healthy fat food choices. Are the fats in your diet the healthy type? Check it out by answering these questions: How Often Do You Eat: Seldom or Never 1–2 Times per Week 3–5 Times per Week Almost 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. R Key Terms FO essential fatty acids, page 18-3 hydrogenation, page 18-8 lipids, page 18-2 trans fats, page 18-9 US E www.healthfinder.gov Good source of information on fats, trans fat, and cholesterol through search terms such as dietary fat and healthy fats. www.epa.gov/ost/fish The Environmental Protection Agency’s site for looking up national and local advisories on fish contamination and consumption. RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O www.nlm.nih.gov/medlineplus/ dietaryfat.html Provides a menu that connects you to sites such as good and bad fats, interpreting blood lipid profiles, benefits of flaxseed, and fat substitutes. OM www links www.nal.usda.gov/fnic Find out more about fats and fat substitutes from the extensive list of topics covered under the search term “fats.” www.mayoclinic.org Healthy fats, bad fats, know your fats, fats and heart disease, and other topics are intelligently covered in sites available through the Mayo Clinic’s home page. Notes 1. Dietary Reference Intakes, Energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. Institute of Medicine, National Academy of Sciences, Washington, DC: National Academies Press; 2002; and Mensink RP et al., Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and serum lipids, Am J Clin Nutr 2003;77:1146–55. 14. Kris-Etherton, New guidelines. 2. Dietary Reference Intakes. 17. Kris-Etherton, New guidelines. 3. Fat in your diet. How low should you go? www.mayoclinic.com/invoke .cfm?id=HQ00670, accessed 6/03. 18. Kris-Etherton, New guidelines. 4. Dietary Reference Intakes. 5. Fats: the good and the bad. www .mayoclinic.com/invoke.cfm?id=NU00262, accessed 9/03. 6. Connor WE. Importance of n-3 fatty acids in health and disease. Am J Clin Nutr 2000;71(suppl):171S–5S. 7. Hepburn FN et al. Provisional tables on the content of omega-3-fatty acids and other fat components of selected foods. J Am Diet Assoc 1986;86:788–93. 15. Stone NJ. Fish consumption, fish oil, lipids, and coronary heart disease. Am J Clin Nutr 1997;65:1083–6. 16. Kris Etherton, New guidelines; and Clarkson TW, Strain JJ, Nutrition factors may modify the toxic action of methyl mercury in fish-eating populations, J Nutr 2003;133:1539S-43S. 19. Krauss et al., Revision 2000. 20. Kris-Etherton PM et al. Polyunsaturated fatty acids in the food chain in the United 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. 22. Krauss et al., Revision 2000. 23. Stuppy P, Transitioning away from trans fatty acids, Today’s Dietitian 2003;Jan.: 12–14; and Dietary Reference Intakes. 24. Dietary Reference Intakes. 8. Everything you always wanted to know about those newfangled eggs. Nutr Today 2003;38:75. 25. Vranico S. PepsiCo sets health-snack effort. Wall Street Journal 2003, Sept. 23, p. B6. 9. Dietary Reference Intakes. 26. Sabar AF et al. Dietary sources of nutrients among U.S. adults. J Am Diet Assoc 1998;98:537–47. 10. Vanschoonbeek K et al. Fish oil, consumption and reduction of arterial disease. J Nutr 2003;133:657–60. FO R 11. Krauss RM et al., Revision 2000: a statement for healthcare providers from the Nutrition Committee of the American Heart Association, J Nutr 2001; 131:132-46; and Kris-Etherton PM et al. New guidelines focus on fish, fish oil, omega-3 fatty acids. AHA Statement. Circulation, 2002;Oct. 18. 12. Kris-Etherton, New guidelines. 13. Connor, Importance of n-3 fatty acids; and Hepburn et al., Provisional tables. 27. Gershoff SN, Nutrition evaluation of dietary fat substitutes, Nutr Rev 1995;53:305–13; and Mattes RD, Position of the American Dietetic Association: fat replacers, J Am Diet Assoc 1998;98:463–8. 28. Mattes, Position of the ADA: fat replacers. 29. Bray GA et al. A 9-month randomized controlled trial comparing fat-substituted and fat-reduced diets in healthy obese men: the Ole Study. Am J Clin Nutr 2002;76:928–34. 30. Mattes, Position of the ADA: fat replacers; and Bray et al., A 9-month randomized controlled trial. 31. Olson RE. Dietary fats: friend or foe? Nutr Notes, American Society of Nutritional Sciences, 2000;Mar.:3. 32. Olson, Dietary fats: friend or foe? 33. Dietary Reference Intakes; and Schwartz J-M et al., Hepatic de novo lipogenesis in normoinsulinemic and hyperinsulinemic subjects consuming high-fat, lowcarbohydrate and low-fat, high carbohydrate isoenergetic diets, Am J Clin Nutr 2003;77:43–50. 34. Dietary Reference Intakes. 35. Trichopoulou A et al. Adherence to a Mediterranean diet and survival in a Greek population. N Engl J Med 2003;348:2599–608. 36. Glew RH et al. Cardiovascular disease risk factors and diet of the Fulani pastoralists of Northern Nigeria. Am J Clin Nutr 2001;74:730–6. 37. Hu FB. The Mediterranean diet and mortality—olive oil and beyond. N Engl J Med 2003;348:2595–6. 38. Dietary Reference Intakes; and Krauss et al., 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). 41. Dietary Reference Intakes. 42. Krauss et al., Revision 2000. RE VI PR EW O P ON E R LY T Y ± N OF OT C E N FO G A R GE SA LE LEA OR R N CL ING AS SR O The Healthy Fats in Your Diet US E UP CLOSE OM Nutrition Feedback for Unit 18 FO R Give 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 or DHA and EPA. Take a point away for each time your answer ended up in the same columns for foods listed in numbers 1, 2, 5, 7, and 8. These foods provide saturated or trans fats. If you have any points left, your selection of food sources of fat regularly include healthy fats.