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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease CHAPTER 2 GUIDELINES FOR A NEW EATING PATTERN In 1988 the surgeon general of the United States said, "For the two out of three adult Americans who do not smoke and do not drink excessively, one personal choice seems to influence long-term health prospects more than any other: what we eat." The scientific evidence linking diet and certain chronic diseases is strong and has been thoroughly documented in Diet and Health. This is not to say that diet is the whole story in causing these diseases. In fact, other aspects of lifestyle such as exercise, smoking, and drinking habits and various inherited, or genetic, factors also contribute to the risk of developing these illnesses. There is little you can do about the genes you inherit from your parents. However, you can modulate their effects through healthy lifestyle choices. Poor diet is one of several known disease-producing elements that you can change to benefit your own and your family's health. The new eating pattern recommended by the Committee on Diet and Health consists of nine dietary guidelines. The guidelines were formulated to reduce the risk of not just one illness but an entire spectrum of chronic diseases. They
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease also take into account whether making a dietary change to reduce the risk for one illness might raise the risk for another illness. The guidelines are presented in a sequence that reflects their relative importance. For example, reducing fat intake has the highest priority because the scientific evidence concerning dietary fats and human health is strongest and the impact on your health is likely to be the greatest. In reading the guidelines, you may want to refer to the definitions of certain nutritional terms given on pages 27 through 31. These terms are explained in greater detail in the chapters to come. THE NINE DIETARY GUIDELINES Reduce total fat intake to 30 percent or less of your total calorie consumption. Reduce saturated fatty acid intake to less than 10 percent of calories. Reduce cholesterol intake to less than 300 milligrams (mg) daily. Americans' diets average about 36 percent of their calories from fat and 13 percent of calories from saturated fatty acids. But a large and convincing amount of evidence shows that diets high in saturated fatty acids and cholesterol are associated with increased levels of cholesterol in the blood stream (serum cholesterol) and the consequent buildup of fatty plaque on the walls of blood vessels. Plaque causes arteries to become narrowed, less elastic, and eventually obstructed and is a cause of heart attacks and strokes. The biggest contributors of saturated fatty acids to Americans' diets are dairy and meat products. Coconut, palm, and palm kernel oils contain higher levels of saturated fatty acids than other vegetable oils, but these oils are not usually eaten in large quantities by Americans. The major food groups providing dietary cholesterol are meat, poultry, and fish; egg yolks (which account for 39 percent of the cholesterol in the food supply); and, to a lesser extent, dairy products.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Evidence from many studies also links high-fat diets to a high incidence of some types of cancer, particularly cancer of the colon, prostate, and possibly breast. In addition, some studies suggest that high-fat diets may lead to obesity. Thus this guideline is based on a wealth of scientific evidence. Reducing the amount of total fat and saturated fatty acids that you eat is likely to lower your risk of atherosclerotic cardiovascular disease, cancers of the colon and prostate, and possibly breast cancer and obesity. You can reduce your intake of fat and cholesterol by substituting fish, poultry without skin, lean meats, and low-fat or nonfat dairy products for fatty meats and whole-milk dairy products; by including more vegetables, fruits, cereals, and legumes in your diet; and by limiting the amounts of oils, fats, egg yolks, fried foods, and other fatty foods that you eat. You might be concerned that by eating less fatty meat and whole-milk dairy products you may not be getting enough iron and calcium. The Committee on Diet and Health found that you can safely reduce fat intake to 30 percent or less of your daily calories without risk of nutrient deficiency because most nutrients are found in the lean part of meat and the nonfat part of dairy products. In addition, children can still get enough calories in a diet containing 30 percent of calories from fat to ensure optimal growth and development. To accomplish this fat intake reduction, you will need to pick lean cuts of meat and low-fat dairy products, keep portion sizes of meat to 3 ounces (6 ounces a day), trim the visible fat, and cook lean. One more word on this guideline: 30 percent of calories from total fat, 10 percent saturated fatty acids, and 300 mg of cholesterol per day are upper limits. Evidence suggests that if adults reduce those levels further, they may gain even greater health benefits. However, you should not attempt to eliminate all fat, especially in the diets of young children, because some fatty acids are essential for adequate growth and development.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Eat five or more servings of a combination of vegetables and fruits daily, especially green and yellow vegetables and citrus fruits. Also, increase your intake of starches and other complex carbohydrates by eating six or more daily servings of a combination of breads, cereals, and legumes. An average serving is equal to one-half cup for most raw or cooked vegetables and fruits, one medium piece of fresh fruit, one-half cup dry or cooked cereal, one slice of bread, or one roll or muffin. The scientific evidence suggests that carbohydrates should account for more than 55 percent of your daily calories (compared to about 45 percent in the average American diet today). Many of the foods listed above are rich in complex carbohydrates but low in fat. Thus they are good substitutes for fatty foods. These foods are also good sources of several vitamins, minerals, and dietary fiber. Studies in various parts of the world indicate that people who habitually consume a diet high in plant foods have low rates of atherosclerotic cardiovascular disease, probably because such diets are usually low in animal fat and cholesterol. The evidence also reveals a link between lower susceptibility to cancers of the lung, stomach, and colon and frequent consumption of vegetables and fruits, particularly citrus fruits, green vegetables, and yellow vegetables, such as carrots and sweet potatoes. Stroke is especially common among blacks and older people of all races. A diet high in potassium and low in sodium may contribute to reduced risk of stroke. Since vegetables and fruits are good sources of potassium, eating the recommended five servings per day of fruits and vegetables can help to lower your risk of stroke. Eat a reasonable amount of protein, maintaining your protein consumption at moderate levels. Protein-containing foods are important sources of amino acids. However, there are no known benefits and possibly
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease some risks in eating diets with a high meat content. Therefore you should not increase your protein intake to compensate for the loss of calories that will result from eating less fat. In fact, most adults already eat considerably more protein than they need. Thus you should consume lean meat, and you may need to select smaller and fewer portions than is now customary in the American diet. One suggestion is to limit meat to 6 ounces a day; a 3-ounce portion of meat is about the size of a deck of cards. Balance the amount of food you eat with the amount of exercise you get to maintain appropriate body weight. Excess weight is associated with an increased risk of several chronic disorders, including noninsulin-dependent diabetes, high blood pressure, coronary heart disease, gall-bladder disease, osteoarthritis, and endometrial cancer. The risks decline following a sustained reduction in weight. The solution to being overweight is not merely reducing calories. In the United States and other Western societies, average body weight is increasing while the overall amount of calories consumed is dropping. The discrepancy between the high prevalence of excess weight and the low energy intake is probably attributable to low levels of physical activity. Thus we as a nation need to exercise more. Moderate, regular physical activity should be a part of everyone's regular routine. It is not recommended that you drink alcohol. If you do drink alcoholic beverages, limit the amount you drink in a single day to no more than two cans of beer, two small glasses of wine, or two average cocktails. Pregnant women should avoid alcoholic beverages. Several studies have shown that drinking moderate amounts of alcohol (one to two drinks per day) may reduce the risk of coronary heart disease, but drinking alcoholic beverages is not recommended as a way to prevent heart disease.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease First and foremost is the risk of alcohol addiction. In addition, drinking too much increases your risk of developing heart disease, high blood pressure, chronic liver disease, some forms of cancer, neurological diseases, nutritional deficiencies, and many other disorders. Even moderate drinking carries some risks in circumstances that require good coordination and judgment—driving and working around machinery, for example. Furthermore, pregnant women, as well as women who are attempting to become pregnant, should avoid alcoholic beverages because of the risk of damage to the fetus. No safe level of alcohol intake during pregnancy has been established. Limit the amount of salt (sodium chloride) that you eat to 6 grams (g) (slightly more than 1 teaspoon of salt) per day or less. Limit the use of salt in cooking and avoid adding it to food at the table. Salty foods, including highly processed salty foods, salt-preserved foods, and salt-pickled foods, should be eaten sparingly, if at all. Because food labels usually state the amount of sodium in a product rather than salt, it should be noted that 6 g of salt equals about 2400 mg of sodium. In parts of the world where people eat more than 6 g of salt per day, hypertension is common. Many Americans regularly eat more than 6 g of salt per day, and this may be one reason that high blood pressure is fairly common in the United States. There is evidence, too, that reducing salt intake further, to less then 4.5 g per day, would have an even greater impact on reducing the risk of hypertension, but 6 g per day is a good start. There is also consistent evidence that excessive consumption of salt-preserved or salt-pickled foods frequently increases the risk of stomach cancer. Some evidence links salt intake itself to stomach cancer, although it is not as persuasive as the connection between high salt intake and hypertension.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Maintain adequate calcium intake. Calcium is an essential nutrient, necessary for proper growth and bone development. Certain groups of people, especially women and teenagers, need to choose their food carefully to obtain enough calcium from their diets. Getting enough calcium during the years when bones are growing will ensure that peak bone mass is achieved. This will decrease the risk of osteoporosis in later life. The best way to get enough calcium is to eat low-fat or nonfat milk and milk products and dark-green vegetables, all of which are rich in calcium. If you follow this advice, you do not need to take dietary calcium supplements. Avoid taking dietary supplements in excess of the U.S. Recommended Daily Allowances (U.S. RDAs) in any one day. Many people in the United States take a vitamin or mineral supplement daily. But except for people with special circumstances, supplements are not really necessary. The American Dietetic Association, American Institute of Nutrition, American Society for Clinical Nutrition, and the National Council Against Health Fraud have described categories of people who may need supplements. These include women with excessive menstrual bleeding; women who are pregnant or breastfeeding; people with very low caloric intakes; some vegetarians; newborns; and people with certain disorders or diseases or who are taking medications that may interfere with nutrient intake, digestion, absorption, metabolism, or excretion. The organizations recommend that individuals see their doctors or a registered dietitian to determine whether supplements are needed. For healthy people eating a varied diet, a single daily dose of a multiple vitamin-mineral supplement containing 100 percent of the U.S. RDAs is not known to be harmful or beneficial. High-potency vitamin-mineral supplements and other supplements such as protein powders, single amino acids, fiber, and lecithin, have no known health benefits. Large dose supplements may,
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease in fact, be detrimental to your health. The best way to get all the nutrients you need is to eat a variety of foods. Maintain an optimal level of fluoride in your diet and particularly in the diets of your children when their baby and adult teeth are forming. The evidence is striking—drinking fluoridated water significantly reduces the risk of dental caries in people of all ages, although it is particularly effective in children when their teeth are growing. There is no evidence that fluoride, at the concentrations used in drinking water, has any adverse effects on health. If the water in your area is not fluoridated at the proper level (0.7 to 1.2 parts per million), you should use a dietary fluoride supplement recommended by the American Dental Association under the direction of your doctor or dentist. To find out if your community's water supply is fluoridated, contact the water authority of the local public works administration. HOW THESE GUIDELINES STACK UP AGAINST OTHERS In the recent history of dietary recommendations for overall health, an expert group from Sweden, Norway, and Finland was among the first to propose in 1968 that the general public should not eat too many calories; should reduce its fat consumption from 40 percent to between 25 and 30 percent of calories; should reduce the amount of saturated fatty acids and increase the amount of polyunsaturated fatty acids in the diet; should reduce consumption of sugar and sugar-containing foods; and should increase consumption of vegetables, potatoes, skim milk, fish, lean meat, and cereal products. Sounds familiar, doesn't it? From the time of the Scandinavian report to this one, seven groups in the United States have proposed dietary
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease guidelines that aim at preventing a range of diseases. These recommendations are shown in Table 2.1. In addition, many expert groups have focused on specific diseases. These recommendations are shown in Table 2.2. In the early 1960s, the American Heart Association became the first U.S. organization to recommend dietary modifications for reducing heart disease. The National Cancer Institute issued its first set of dietary guidelines for cancer prevention in 1979, and the American Diabetes Association contributed dietary recommendations for avoiding noninsulin-dependent diabetes in 1987. The two tables show that there is general agreement among the many sets of recommendations. The few differences of opinion that do exist stem largely from incomplete evidence on the link between diet and chronic diseases. Most of the recommendations deal with the type and amount of fat and cholesterol; complex carbohydrates, fiber, and sugars; sodium, salt, or salty foods; alcoholic beverages; and variety in the diet, as well as body weight and exercise. Some also address avoiding toxic substances, and two reports focus specifically on dietary supplements. A few of the recommendations specify quantities of nutrients—percentage of calories from fat or grams of salt per day, for example. Others are more general in nature, suggesting that people should eat more of or avoid a particular dietary component. In general, it is striking how much the recommendations from different sources agree. For example, because obesity is a major contributor to several chronic diseases, most expert panels have recommended maintenance of an appropriate body weight; some have even proposed height/weight tables such as the ones used by the life insurance industry (see Chapter 4). The Eat for Life guidelines go along with the recommendation to keep to an appropriate weight, but here it is emphasized that you should balance your physical activity
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease TABLE 2.1 Dietary Recommendations to the U.S. Public, 1977 to 1990 Maintain Appropriate Body Weight, Exercise Limit or Reduce Total Fat (% kcal) Reduce Saturated Fatty Acids (% kcal) Increase Polyunsaturated Fatty Acids (% kcal) Limit Cholesterol (mg/day) Limit Simple Sugars U.S. Senate (1977) Yes 27-33 Yes Yes 250-350 Yes Council on Scientific Affairs (AMA) (1979) Yes No No No No Yes DHEW (1979) Yes Yes Yes NS Yes Yes NRC (1980) Yes For weight reduction only No No No For weight reduction only USDA/DHHS (1980, 1985) Yes Yes Yes No Yes Yes DHHS (1988) Yes Yes Yes No Yes Yes USDA/DHHS (1990) Yes Yes Yes No Yes Yes NOTE: NC = No comment; NS = Not specified. AMA = American Medical Association; DHEW = Department of Health, Education, and Welfare; NRC = National Research Council; USDA = U.S. Department of Agriculture; DHHS = U.S. Department of Health and Human Services.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Increase Complex Carbohydrates (% kcal from total carbohydrates) Increase Fiber Restrict Sodium Chloride (g) Moderate Alcohol Intake Other Recommendations Yes Yes 8 Yes Reduce additives and processed foods NC NC 12 Yes Consider high-risk groups Yes NS Yes Yes More fish, poultry, legumes; less red meat No No 3-8 For weight reduction only Variety in diet; consider high-risk groups Eat adequate starch and fiber Yes Yes Variety in diet; consider high-risk groups Yes Yes Yes Yes Fluoridation of water; adolescent girls and women increase intake of calcium-rich foods; children, adolescents, and women of child-bearing age increase intake of iron-rich foods Choose diet with plenty of vegetables, fruits, and grain products Yes Yes Variety in diet SOURCE: National Research Council. 1989. Diet and Health: Implications for Reducing Chronic Disease Risk. National Academy Press, Washington, D.C.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease with the amount of food you eat to avoid obesity. Merely watching your calories is not the best approach to weight control. And along with the American Dietetic Association, the committee recommends that you avoid gaining and losing weight repeatedly. Perhaps the most common and consistent recommendation in these reports is to limit how much fat you eat. In most cases, the experts agree that fat should account for no more than 30 percent of your total calories. Most experts also suggest reducing the amount of saturated fatty acids you eat to less than 10 percent of total calories. There is less agreement on recommendations concerning cholesterol in the diet. Most organizations advise that you eat less than 300 mg of cholesterol a day. Lower goals may be beyond the reach of the typical U.S. adult and thus may discourage people from trying to meet them. The committee goes along with the consensus on fats and cholesterol. But you should keep one thing in mind: the dietary pattern recommended in Eat for Life is only moderately low in fat. The scientific evidence suggests that adults may achieve additional health benefits by cutting even more fat, saturated fatty acids, and cholesterol from their diets. Most groups also advise that you should eat more complex carbohydrates to replace the calories from the fat that you cut from your diet. Some organizations have also singled out dietary fiber as something you should eat more of or refined sugar as a substance you should eat less of. Eat for Life agrees with these other reports in suggesting that you eat more vegetables, grains, and legumes as sources of complex carbohydrates. However, this book also tells you how many servings per day of these foods you should eat. But unlike some guidelines, the ones in Eat for Life do not specifically include one to increase the amount of dietary fiber you eat. The Committee on Diet and Health believes that the evidence supports a recommendation to eat more fiber-rich foods (fruits, vegetables, cereals, and grains) rather
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease than eating more fiber per se. Nevertheless, following the guidelines in this book will provide you with more than enough fiber. Few reports deal with how much protein you should eat, although some say you should eat less meat and more vegetable products. If you adopt the Eat for Life pattern, the amount of protein you eat will remain about constant or perhaps drop some. The Eat for Life guidelines on salt and alcohol are also consistent with those of other groups. Other reports have addressed specifically the need for vitamins and minerals. If you follow the guidelines in this book you will have no worries about getting the full range of nutrients in the amounts that you need. Like other books, Eat for Life suggests that you avoid taking dietary supplements in excess of the U.S. RDAs in any one day. Eat for Life—and its parent report Diet and Health—differs from these other reports primarily in scope. This report looks at the effect of diet on a whole spectrum of chronic diseases influenced by diet. Developing the guidelines in Eat for Life required the committee members to analyze and compare recommendations that others have made for individual diseases to ensure that a guideline to reduce the risk of one chronic disease might not inadvertently increase the risk of another. By taking such a wide-ranging look at diet and health, the guidelines in Eat for Life can take into account competing risks from different dietary components and food groups. For example, recommendations to increase calcium intake to provide possible protection against osteoporosis might conflict with recommendations for heart disease prevention, because milk and milk products—the major source of calcium in the U.S. diet—are also major sources of saturated fatty acids. Therefore a guideline whose goal was to both maintain adequate bone mass and prevent heart disease would have to stress low-fat or nonfat dairy products.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease YOU BENEFIT, THE NATION BENEFITS There are two approaches to reducing dietary risk factors for chronic disease. The first is to make recommendations for individuals who are at higher risk, an approach that requires identifying and treating those who stand a good chance of developing a chronic illness. For example, high blood pressure, obesity, high serum cholesterol levels, atherosclerosis, and certain cancers appear to occur more frequently in particular families. The second method is to make recommendations aimed at the general public, hoping in the process to help everyone who might be at some risk for developing chronic diseases. In a perfect world, dietary guidelines would be tailored for each person's individual biochemical needs. Such guidelines would account for a person's age, sex, heredity, body build, occupation, and other special conditions, such as pregnancy or illness. These would be ideal because each person is unique. For conditions such as high blood pressure or elevated serum cholesterol levels, physicians can identify those of us at risk—in this case for stroke and heart disease, respectively—by using simple diagnostic tests. For other conditions where specific tests are lacking—such as breast cancer—a strong family history of the disease may suggest that special preventive approaches are needed. But for the most part, it is usually not feasible to identify people at high risk for a disease or to screen the entire population, and so dietary guidelines must apply to the general public. By reaching a broader group of people, dietary recommendations aimed at reducing the risk in the general population can provide major health benefits for the nation. One study estimated that making changes similar to those in the Eat for Life guidelines could prevent more than 100,000 deaths annually from coronary heart disease, the nation's leading killer. In fact, the death rate for heart disease, which claims nearly
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease a million lives a year, has already declined 33 percent since 1970, and a large part of this decline is related to the dietary changes some people have made already. You do not have to have remarkably high serum cholesterol levels to benefit from these guidelines, either. The vast majority of people who die from cardiovascular diseases have only moderately high total serum cholesterol levels: less than 240 milligrams per deciliter (mg/dl) but greater than 200 mg/dl. For moderately elevated total serum cholesterol, every 1 percent reduction in total serum cholesterol level in the U.S. population reduces the risk of coronary heart disease by 2 to 3 percent. Incidences of other disease would be reduced as well. Evidence on the connection between diet and cancer suggests that following these guidelines could eventually result in as much as a 35 percent reduction in cancer deaths in the United States. Hypertension affects an estimated 60 million people in the United States. If lowering salt intake cut that number by as little as 10 percent, that would mean 6 million more people a year would have less risk of stroke and heart disease. Furthermore, although genetic factors can affect an individual's susceptibility to diseases, these inherited factors are not the entire story. Witness the fact that immigrants tend to acquire the disease rates of their adoptive countries, presumably because they adopt the lifestyle and the diet of the natives. Therefore the guidelines in Eat for Life are for everyone except infants and children under 2 years to follow. Children, of course, will eat smaller serving sizes than the ones recommended for adults. Adhering to these guidelines should reduce the risk of chronic disease for everyone in the population—some of us will benefit more, but all of us are likely to benefit to some degree. It is important to note, however, that even though the guidelines are written for the general public, the goals expressed are goals for the individual, not the general population. For example, the guideline that states that you should get less than 10 percent of your total calories from saturated
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease fatty acids comes from evidence that average levels of total serum cholesterol are low in cultures in which the average consumption of saturated fatty acids is less than 10 percent of calories and that these cultures are relatively free of heart disease. However, the way the guideline is stated here is that each one of us—not just the nation as an average—should lower the amount of saturated fatty acids we eat to less than 10 percent. Figure 2.1 illustrates this difference using serum cholesterol levels as the example. The dashed line shows serum cholesterol levels in a particular population ranging from 140 mg/dl to 260 mg/dl, with an overall average of 200 mg/dl. In that group of people, heart attacks are not common, but those few people who do have heart attacks tend to be those with cholesterol levels above 200 mg/dl. The solid line indicates a population in which almost everyone has serum cholesterol levels below 200 mg/dl. As a result, the average cholesterol level for the whole population FIGURE 2.1 Hypothetical distributions of serum total cholesterol levels in a population that has achieved a public health goal of 200 mg/dl (dashed line) or a goal that all individuals lower their serum cholesterol to 200 mg/dl or less (solid line). For the lower goal, the range of cholesterol levels is assumed to be narrower. SOURCE: National Research Council. 1989. Diet and Health: Implications for Reducing Chronic Disease Risk. National Academy Press, Washington, D.C.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease is approximately 150 mg/dl. All the members of this population are at low risk for heart disease, and although the level of heart disease is low in the population represented by the dotted line, it would be even lower in the population represented by the solid line. There is another way to think about these guidelines and their possible positive effect on your health. Chances are good that your parents had you vaccinated against polio. The chances were small that you would ever catch polio, and even if you had caught polio your genetic makeup might have spared you permanent disability. Nevertheless, your parents decided to protect you against polio because even though the risk was small, the consequences could have been devastating. The same is true here, except that the risk of developing cancer, coronary heart disease, stroke, or other chronic illness is much higher than that of catching polio. Each of us has a different genetic makeup that gives us different susceptibilities to chronic diseases; for example, some may be at high risk for cancer of the colon but at lower risk for cardiovascular disease, and vice versa. Because we are not able at this stage to distinguish who is at high or low risk for either of these diseases, we have to assume that everyone eating high levels of fat is at high risk. So until medical science can screen each and every one of us for our susceptibility to all chronic diseases, it would be wise for all of us to follow the dietary guidelines in Eat for Life. DIETARY TERMS Basic nutrition is covered more completely in Chapter 3, but a brief introduction here will make it easier to understand the guidelines. Fats (also called lipids) are a large family of compounds that do not mix with water. Lard, butter, margarine, shortening,
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease and cooking oil are almost pure fat; meat, dairy products, chocolate, cakes and cookies, nuts, and a few fruits and vegetables contain significant amounts of fat. Fats are important sources of energy in the diet. Fatty acids are the major components of fats. They come in three basic types: saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. Saturated fatty acids are found mostly in animal fats—lard, butter and other dairy products and meat, for example—where as monounsaturated and polyunsaturated fatty acids come mostly from vegetable sources. Cholesterol is another member of the lipid family. It is a structural component of cell membranes. Some hormones and vitamin D can be formed from cholesterol. The body can make sufficient cholesterol to meet its needs. The main dietary sources of cholesterol are egg yolks, meat, poultry, shellfish, and whole-milk dairy products. In fact, cholesterol is found only in food of animal origin. Since cholesterol is a fat-soluble compound, it does not float freely in the blood stream, which is mostly water. Instead, cholesterol travels through the blood stream in gigantic molecules made of fat and protein and called lipoproteins. Most of the blood cholesterol is carried in low-density lipoproteins (LDL). Cholesterol is also carried in high-density lipoproteins (HDL). Cholesterol in LDL and HDL is called, respectively, LDL-cholesterol and HDL-cholesterol. The term ''total serum cholesterol" refers to the sum of cholesterol in all the lipoproteins. Medical experts strongly recommend that total serum cholesterol be below 200 milligrams per deciliter (mg/dl). Protein is the major structural material in almost all living tissue except bones. Hair, skin, nails, and muscles are mostly protein. There are thousands of different proteins in the human body, each with a unique function, but they are all
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease made from smaller units called amino acids. The body breaks down dietary protein into amino acids and then uses the amino acids in proteins. All told, there are 20 common amino acids in proteins. The body can manufacture 11 of them, but it must obtain the other 9, the so-called essential amino acids, from food. Animal proteins, except for gelatin, and soy proteins contain all the essential amino acids in sufficient quantities and are known as complete proteins. Most plant proteins are low in one or more of the essential amino acids, and so it is necessary to combine different protein sources to make up for these shortages. For example, peanut butter and bread combined are a complete protein source. So, too, are rice and beans when eaten in the same meal. Such combinations are called complementary proteins. Carbohydrates are the body's best source of energy, and, in fact, they are the most important source of calories for much of the world's population because of their relatively low cost and wide availability. For our purposes, there are three types of carbohydrates: simple carbohydrates, digestible complex carbohydrates, and indigestible complex carbohydrates. Simple carbohydrates, such as glucose, fructose, sucrose, and lactose, are also called sugars. Some sugars taste sweet—such as those in table sugar, honey, fruits, molasses, and maple syrup, whereas others, such as those in milk and malt, have little taste at all. The body readily digests and metabolizes simple carbohydrates. Complex carbohydrates, or polysaccharides, are large molecules made from hundreds of sugar molecules hooked together. In essence, sugar molecules are the building blocks of carbohydrates in the same way that amino acids are the building blocks of proteins. Starches are the most abundant polysaccharides in the diet and occur in many foods, including cereals, breads, dry beans, peas, and potatoes. The body digests polysaccharides into sugars.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Indigestible complex carbohydrates, also called fiber or roughage, are large molecules as well, but the sugar building blocks are linked together in such a way that the body cannot break them apart. Because of this, fiber does not supply energy or nutrients to the body, but it does aid in digestion and elimination. Cellulose and pectin, the two most important indigestible complex carbohydrates, are plentiful in bran, whole-grain cereals and breads, fruits, and vegetables. Vitamins fall into two families, fat-soluble vitamins and water-soluble vitamins. Fat-soluble vitamins are often found together with fats in food. Vitamins A, D, E, and K are fat-soluble vitamins. Because water-soluble vitamins mix readily with water, excess water-soluble vitamins are not stored in the body but are washed out in urine. Vitamins C (ascorbic acid), B1 (thiamin), B2 (riboflavin), niacin, B6 (pyridoxine), pantothenic acid, biotin, folacin, and B12 (cobalamin) are water-soluble vitamins. Minerals, or mineral salts, have a variety of uses throughout the body and are involved in almost every aspect of its functioning. The minerals calcium, phosphorus, and magnesium are required in relatively large amounts. Calcium, for example, is the most abundant mineral in the body and accounts for nearly 2 percent of body weight. More than 99 percent of the body's calcium is in the bones and teeth, but calcium is also essential for nerves and muscles to work properly. The body also requires smaller, or trace, amounts of at least 10 other minerals. These trace elements include chromium, cobalt, copper, fluoride, iodine, iron, manganese, molybdenum, selenium, sulfur, and zinc. All trace elements are toxic if too much is consumed over long periods of time.
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Eat for Life: The Food and Nutrition Board's Guide to Reducing Your Risk of Chronic Disease Three other minerals, known as electrolytes, are important components of all body fluids. These minerals are sodium, potassium, and chloride. Table salt is the compound sodium chloride. Meat, peanuts, potatoes, and many fruits and vegetables are rich in potassium.
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Representative terms from entire chapter: