DISCUSSION OF PROPOSED CHANGES
In its discussions, the Dietary Guidelines Advisory Committee determined that research conducted since 1990 continues to support most of the text of the third edition of the Dietary
Guidelines. This section of the report describes suggested changes to the third edition. For the most part, these changes are aimed at clarification and emphasis of key points. Overall, the committee suggests that the fourth edition --
* Define terms more precisely
To help clarify discussion, the committee suggests that specific terms be given operational definitions in the text.
* Add section headings as subtitles
To guide readers to key points and to make the text easier to read, the committee suggests that text sections be headed by titles or statements related to their content. For example, the first sentence in the 1990 Guidelines is used as the first title in the 1995 text.
* Refer readers to the Food Guide Pyramid
The pyramid was published by USDA and HHS in 1992 as an implementation guide to the 1990 Guidelines. The committee views this publication as a helpful educational tool to be used in conjunction with the Dietary Guidelines and recommends that the pyramid graphic replace the former representation of the recommended Daily Food Guide. This recommendation is made with an understanding that the purpose of this graphic is to explain and interpret rather than to determine the Guidelines. Thus, revisions to the pyramid in accordance with revisions to the Guidelines are considered appropriate.
* Refer readers to the new food label
The Nutrition Labeling and Education Act of 1990 (NLEA) and subsequent Food and Drug Administration regulations specify nutrition information required on food labels. The committee suggests that the guidelines refer readers to relevant sections of the food label and encourage them to use the label to make food choices consistent with the Guidelines. Including examples of the food label will help readers to better understand key points and facilitate cross-referencing.
* Add tables to the text
The committee suggests the addition of tables listing a few food sources of key nutrients -- those most limited in the diets of certain population groups. Tables have been added for food sources of calcium, iron, carotenoids, folate, and potassium.
* Omit specific medical criteria
The committee suggests that the text of the Guidelines relate specifically to dietary issues and omit specific guidelines for such medical advice as desirable levels of blood cholesterol, blood pressure, and blood glucose.
* Limit quantitative recommendations
The committee suggests continuation of the quantitative guidelines for percentage of energy from fat and saturated fat given in the third edition. The text refers readers to food label standards for cholesterol and sodium without making specific recommendations.
The committee received many communications from the public and some professionals, requesting that the guidelines quantify the recommendations for intakes of other nutrients (including sugar, fiber, mono- and polyunsaturated fats, trans fatty acids, and antioxidants). The committee has concluded that the state of scientific evidence is insufficient at present to provide quantitative guidelines for most of these nutrients that would be applicable to both sexes and all ages above 2 years. In addition, the committee is concerned that emphasis on numeric goals and limits for nutrients adds undue complexity to the food selection process for most consumers.
Introduction to the Bulletin
The committee suggests that the introduction be designed to provide a broad overview of the purpose and content of the specific guidelines, to introduce readers to the principal concepts, and to avoid redundancies. Therefore, the committee recommends that the introduction state basic principles of healthful diets, explain how diet affects health, define basic terms related to food consumption, nutrient requirements, and energy balance, and refer readers to common sources of information about healthful diets.
Much of the information is contained in the 1990 text. To clarify that text and expand its content, the committee suggests the following additions:
* Explain basic concepts of food composition
The committee thinks it will be helpful to readers to explain basic concepts of nutrition pertinent to the various guidelines: Humans require nutrients and energy; foods contain energy, nutrients, and other important components in different proportions; and food proteins, fats, and carbohydrates contain different amounts of energy.
* Explain the basis of body weight
To relate healthful diets to body weight, the committee suggests that the introduction should emphasize the importance of both energy intake and expenditure in weight maintenance.
* Distinguish the Dietary Guidelines from Recommended Dietary Allowances
The committee thinks it is helpful to readers to clarify the difference between the nutrient-based recommendations of the RDA's and the food-based recommendations of the Guidelines, particularly because RDA's are the basis of some of the information provided on food labels.
Eat a Variety of Foods
The wording of this guideline and its priority as the first of the Dietary Guidelines remainunchanged in the 1995 version. The importance of this guideline stems primarily from nutritional adequacy concerns. Studies of the association of dietary variety with nutrient intake have indicated beneficial effects of variety on meeting RDA's but not on meeting objectives with respect to moderating fat, saturated fat, or sodium intake (1,2). The recommended text for 1995 attempts to focus this guidance more specifically on dietary adequacy. General statements equating varied diets with healthful diets and referring to prevention of chronic diseases have been moved to the expanded introduction. In this way, the variety guideline becomes a less global statement of positive dietary values and a more focused, stronger statement indicating that a narrow set of food choices may result in inadequate intakes of essential nutrients. The phrase and other substances needed for health has been added throughout this guideline to emphasize that the term nutrients does not cover all of the food components that may be beneficial. This guideline continues to stress the total eating pattern in order to provide a context for integrating and putting into perspective the guidance regarding specific nutrients or types of food.
The committee recognizes a need to counteract the impression that the Dietary Guidelines overall foster a negative view of many foods as "bad" for health, by suggesting language that is deliberately positive and intended to convey a message of enjoyment of foods as an underlying principle. The text has been revised to explain systematically what is meant by variety, why it is generally important, and where certain population groups have special concerns in relation to food choices for nutritional adequacy.
New areas of emphasis include an explanation of the principle of dietary variety in relation to vegetarian diets and a more comprehensive explanation about supplementing nutrients or other food constituents in the diet, including comments about dietary fiber supplements and fortified and enriched foods.
Present the Food Guide Pyramid and serving sizes
The committee recommends inclusion of the Food Guide Pyramid graphic in this edition and considers the variety guideline the most appropriate place to introduce this visual aid. Because the serving sizes used in the pyramid, food labels, food composition databases, and food exchanges are not the same and are frequently smaller than servings typically consumed by the public, the committee thinks it is helpful to define serving sizes in a table. For the sake of consistency, the table gives serving sizes derived from the pyramid.
Emphasize the base of the pyramid as the foundation of meals
The guidance to choose the largest number of servings of food from the grain products group represents a shift in the current dietary pattern of most Americans. The wording emphasizes building meals to encourage an integrated perspective on overall food choices.
Choose different foods within each food group
There is no strong evidence linking food variety within groups to overall dietary adequacy beyond effects accomplished by choosing foods from different groups. However, the committee considers it important to educate consumers about the differences in food composition (in relation to nutrients and other potentially beneficial substances) within food categories.
What about vegetarian diets?
Vegetarian diets are not discussed in the 1990 Guidelines. The committee considers that the absence of clear advice in relation to vegetarian diets is a deficiency of the Guidelines, given the increasing public interest in this dietary regimen. In adding this section the objective is to acknowledge the practice of vegetarianism, demonstrate the compatibility of vegetarian diets with the advice in the Dietary Guidelines, and draw attention to the specific nutritional adequacy issues associated with limitation on intake of products of animal origin (3).
Foods vary in content of calories and nutrients
The low caloric intake levels associated with sedentary lifestyles, coupled with a limited variety of foods, is likely to result in marginal intakes of some essential nutrients (4). The language in this section attempts to address nutrient density in a factual manner, highlighting the differences in the amounts of vitamins and minerals relative to calories in various foods. Thus, not only are there statements about the need for variety to obtain the different nutrients contained in different types of foods but also there are statements about the need for attention to the relative proportions of nutrients in foods used to obtain calories, particularly when food intake is restricted.
Special needs, fortified foods, and supplementation
The special considerations related to adequacy of nutrients during growth and for women are highlighted here as an appropriate elaboration of the principle of dietary variety and lead into a discussion of supplementation. The proposed text argues more strongly than did the 1990 edition that consumers should not routinely rely on supplements to meet nutritional goals.
The committee recognizes a need to clarify the role of enriched and fortified foods in the diet. To help avoid a perceived contradiction in the advice to consume certain enriched products and not to rely on supplements and by implication fortified foods, a distinction is made between foods to which nutrients are added as a matter of national policy and other foods to which nutrients may have been added optionally. Consumers are advised to consider the use of these foods in the context of their total diets with the aid of the information on food labels. While the general recommendation is not to rely on supplements, examples are given of circumstances in which supplements may be needed. Concerns about problems associated with fiber supplements make it necessary to mention them explicitly in this section.
Advice for today
This section restates the overall principle of dietary variety beginning with a positive statement about enjoyment of foods. A reminder to use food labels to help guide dietary choices that are in accordance with the other guidelines is considered to be very important, since choosing a variety of foods does not necessarily yield an eating pattern that is low in fat, cholesterol, or sodium or sufficient in fiber.
Balance the Food You Eat With Physical Activity.
Maintain or Improve Your Weight.
The committee suggests several substantive changes in this guideline. The revised title reflects a new emphasis on energy balance as the appropriate approach to weight maintenance. Overall, the revised guideline places less emphasis on weight loss and more emphasis on weight maintenance. The recent well-documented increases in the prevalence of obesity emphasize that weight control represents the essential first step toward a reduction in the prevalence of obesity in the population.
The previous guideline was based on the presumption that a healthy weight could be maintained or achieved. Although the maintenance of a healthy weight is reasonable for those who are already within the healthy weight guideline, the high rates of relapse after weight loss suggest that this goal may be impossible for the large number of overweight persons in the United States. Therefore, the guideline now emphasizes the importance of weight maintenance at any age. Its current wording is based on the premise that the prevention of weight gain at any age is achievable and will have a profound effect on the morbidity and mortality associated with weight gain (5-7). The goal of weight maintenance differs from the goal of achieving a healthy weight for all Americans. However, weight maintenance for the population represents the necessary first step to achieve a healthy weight.
Definition of Healthy Weight
Maintenance of a healthy weight is still a major goal but is now secondary to weight maintenance at any level. Use of a cutoff Body Mass Index (BMI) to establish the upper bound of a healthy weight is based on the use of a definition of obesity that is related to pathologic sequelae rather than an arbitrary definition. The cutoff point used to define obesity will depend on whether the cutoff point is based on morbidity or mortality. For example, several recent studies designed to address this problem have demonstrated that mortality increases significantly above a BMI of 25 (5-7). However, the prevalence of diabetes begins to increase well below a BMI of 25 (8,9). Because the most significant and reliable consequence of a disease is mortality and because the designation of obesity at a point below a BMI of 25 will label well over half of the population obese, the committeesuggests that use of a BMI of 25 to define the upper boundary of healthy weight appears the most reasonable definition. Use of this cut point is consistent with the cut point recommended by the American Institute of Nutrition Consensus Conference (10). Because body fat cannot be readily measured, weight appears to be the most appropriate surrogate.
Inclusion of a graphic that shows a graded risk for weights for height above a BMI of 25 has substantial merit, insofar as a graded risk is consistent with the dose effect of a rising BMI and helps move the perception of weight from an either-or discussion. The principal difficulty with a graded risk approach is the determination of where to draw the lines. The use of colors to indicate that the risks are not clear-cut is a format preferable to the use of lines. A relative risk of two for death and diabetes occurs between a BMI of 25 and 33 (range 26.9-32.9)(references 5-9). Although arbitrary, these data would suggest that a risk-related gradient should utilize a BMI of 25 to 28 or 29. Use of shading reflects the lack of a clear-cut point or consensus on where the line should be drawn and emphasizes that risk varies with the severity of the disease.
The area below the healthiest weight represents a BMI of less than 19 (15th percentile). This area is not named because it is not clear whether a weight below this BMI is unhealthy. Further data are necessary to demonstrate the point at which the risks associated with a low BMI increase. The revised guideline states that there may be risks associated with a low BMI, particularly if involuntary weight loss has occurred.
Age-neutral adult standards
Based on published data, there appears to be no justification for the establishment of a cut point that increases with age. Although the nadir of mortality curves increase with age in several studies, these studies have failed to control for a history of smoking, which appears to affect mortality at all ages. Furthermore, several large published studies fail to show an increase with age in the BMI associated with the lowest mortality (5,7,11).
Body fat distribution
Fat distribution and total body fat affect the risks of obesity-associated co-morbidities. The current guideline places less emphasis on how fat distribution should be determined and more emphasis on factors that affect fat distribution. Although waist-to-hip ratio has been used as a measure of fat distribution, more recent data suggest that waist circumference may be as powerful as the waist-hip ratio in the prediction of morbidity. However, no data have been published that permit recommendations regarding limits on the growth of waist circumference with age. Heredity accounts for approximately 20-30 percent of the variance in fat mass, fat- free mass, and fat distribution (12). However, central fat distribution appears to increase with cigarette smoking (13-15), stress (14,16), and alcohol use (15,17). Exercise represents one of the few factors that reduces central body fat (14,15,18). Most of the studies of the association of smoking, alcohol intake, or activity with fat distribution control for confounding variables such as BMI and other behaviors that might influence fatness and fat distribution.
Goal for weight loss
The committee suggests that recommendations for weight loss should be based on a loss of between 5-10 percent of body weight (19). This recommendation has a solid basis in literature and eliminates the need for a weight-based recommendation that may not be applicable across all increased BMI categories. A specific recommendation appears more appropriate than a general recommendation that is subject to misrepresentation.
Activity, health, and weight
The revised guideline emphasizes the importance of activity for both weight control and health. The role of exercise on health depends strongly on the outcome variable of interest. For example, the effects of activity on fitness appear dissociated from the effects of activity on lipoprotein levels. In a walking intervention designed to have three groups of women walking 4.8 km at different rates 5 days per week, maximal oxygen uptake increased in a dose-response manner, but high-density lipoprotein levels were not dose related and increased significantly in all groups (20). However, in comparisons of the same quantity of moderate to vigorous exercise conducted as a single interval or divided into three separate intervals, comparable effects on fitness were noted (21), but high-density lipoprotein levels increased significantly only in the group that exercised at intervals (22).
Weight has rarely been used as an outcome variable in studies of the effects of activity. However, fitness, defined as treadmill time, appears inversely related to activity. The fitness
standard that appears to produce the lowest mortality is equivalent to a brisk walk of 30-60 minutes per day (23).
The effects of activity on morbidity and mortality, the dose-response nature of the effect, and the recognition that intermittent bouts of exercise may have the same cardiovascular benefits as continuous exercise led to the recommendation that all adults should accumulate 30 minutes or more of moderate-intensity physical activity on most, or preferably all, days of the week (24). In most of the major studies of cardiovascular mortality (24), the relative effect of some exercise compared to none appears to have the greatest effect at moderate levels of physical activity. The effect of some exercise compared to none on morbidity appears comparable (25). Based on the observation that an activity equivalent to 1 MET is about 1.2 kcal.min-1 or approximately 1 kcal.kg-1.hr-1, these recommendations would suggest the equivalent of 10-18 MET's per week. Although the goal of an expenditure of 10-18 MET's per week represents the ideal, the best outcome would be for those at almost any level of activity to increase their activity further. Therefore the revised guideline advises that a sedentary individual should become nonsedentary, and individuals who participate in light activity try to increase their activity further. A list of examples of moderate activity is included to aid in implementation.
Reductions in sedentary activity are also addressed in this revision. Television viewing represents the most important sedentary activity of Americans. For example, adult women aged 18 years and older spend almost 35 hours per week watching television (26). Television viewing has been linked to obesity in adults and children (27,28). Therefore, the guideline suggests not only an increase in moderate activity but also a decrease in sedentary activity as approaches to the maintenance of energy balance.
Issues related to weight loss in children and the elderly
The text emphasizes the need for children to eat healthful diets in order to promote normal growth and development at any body weight. To prevent overweight, the text emphasizes the importance of physical activity rather than food restriction. It notes that major efforts to change children's eating habits should be discussed with a physician or nutritionist.
The text points out that older adults should strive to maintain -- neither gain nor lose -- weight. Weight lost late in life is primarily muscle; physical activity helps to preserve fitness and should be encouraged.
Choose a Diet With Plenty of Grain Products, Vegetables, and Fruits
The committee suggests that this guideline be more prominently displayed by following immediately after the weight guideline. A small change in wording, placing grain products first in the food list, makes the heading consistent with the Food Guide Pyramid.
In the 1990 Dietary Guidelines the primary emphasis in this guideline was consumption of these foods as a source of dietary fiber and starch. The revised guideline emphasizes the contribution of these foods to total nutrient intake. These foods are highlighted as sources of vitamins C and B6, carotenoids and other antioxidant nutrients, folate, potassium, calcium, and magnesium and are noted typically to be low in fat.
The committee recommends the above-stated revision based on public awareness of epidemiological data that associate the intake of antioxidant nutrients with a lower risk for
noncommunicable diseases. Most of the epidemiological data are based on dietary patterns that include intake of these nutrients from foods (29-31). The committee wants to emphasize to consumers that the advantage of consuming these nutrients from foods is that food contains a variety of nutrients as well as other compounds that may contribute to lower risk of chronic
disease. Despite this evidence, most Americans consume less than the recommended number of servings of fruits, vegetables, and grains (32,33).
With the broader scope of this recommendation (that is, vitamins, minerals, antioxidant nutrients, lower fat content, as well as fiber and starch) and with the focus of the guideline on positive actions to modify dietary pattern, it seems more appropriate to have this guideline follow more directly after the advice to enjoy a variety of food and precede the more proscriptive recommendations on fat, saturated fat, cholesterol, sugar, salt, and alcohol.
Food versus nutrients
There is considerable information that strengthens our understanding of the relationship between the consumption of plant foods and lower risk of heart disease and cancer, including the understanding that many factors in these foods are likely to contribute to lower risk (34).
Epidemiological and clinical data have been used to associate the consumption of specific nutrients with lower risk of chronic disease. The committee strongly recommends that consumers be made aware of the importance of foods in providing these nutrients as well as other compounds that may be beneficial to health. Since the last Dietary Guidelines were published, FDA has approved health claims for products containing grains, fruits, and vegetables that link them to a lower risk of heart disease and cancer (35,36).
Survey data reveal that most Americans consume less than the recommended number of servings of these foods (32,33). The guideline supports the HHS Five a Day for Better Health campaign, which is designed to increase the consumption of fruits and vegetables.
Inclusion of folate
Evidence developed since 1990 clearly supports a claim that points to the importance of folate adequacy in the first trimester of pregnancy in the prevention of neural-tube defects (NTD) in infants (37-40). Causality has been proved by administration of pure folic acid. The potential role of food-folate has not been explored, but guidance and information on the content of folate in plant foods is prudent, surely harmless, and possibly beneficial. The U.S. Public Health Service, in fact, has issued a recommendation encouraging all women of childbearing age who are capable of becoming pregnant to consume 0.4 mg of folic acid per day (not to exceed 1 mg total folate) for the purpose of reducing their risk of NTD (41).
Epidemiologic data point to an association of elevated homocysteine levels in the blood with cardiovascular disease and stroke in the elderly (42-45). Of the nutrients involved in the metabolic homocysteine pathway (folate and vitamins B12 and B6), folate appears to be the most important. Lack of intervention trials precluded inclusion of this information in the consumer bulletin. A future committee may want to consider the evidence when it becomes available. Still, the advice to foster consumption of folate-rich foods is prudent and is made in the bulletin.
Comments to the committee suggest that consumers have a poor understanding of the role of dry beans in the diet. Although beans are classified as a meat alternative because of their protein content, consumers can eat more of these products than the recommended 2-3 servings of meat or meat alternatives by counting them as servings of vegetables instead. The committee is clarifying this point.
Starchy foods such as breads, cereals, beans, potatoes, and rice are relatively low in fat. These foods, however, may be high in fat if spreads, shortenings, or oils are added during preparation or at the table. Advice is included so that consumers recognize that fat added during preparation is an important factor in determining whether these foods contribute to lowering total fat intake.
Recommendations to increase consumption of fruits and vegetables have often been interpreted to mean consumption of fresh produce. In many situations poor availability, high cost, or poor quality in selection of fresh produce may lead to insufficient consumption of these important foods. The committee wants consumers to be aware that processed products are a reasonable way to meet the recommendations in this guideline.
Choose a Diet Low in Fat, Saturated Fat, and Cholesterol.
The committee concurs with the 1990 wording but places this guideline in fourth position, after the guideline on grains, vegetables, and fruits -- the foods that are the foundation of a healthful diet. Revisions of the text are for purposes of clarification and updating.
The introductory paragraph relates both the positive and negative aspects of dietary fat to the total diet. The importance of essential fatty acids and fat-soluble vitamins that are associated with dietary fat are indicated. The paragraph also points out that Americans are eating less total fat, saturated fat, and cholesterol than formerly. These positive statements are intended to place in context the need to continue to emphasize further reduction of the average consumption of fat, saturated fat, and cholesterol, given the continued high risk of atherosclerotic vascular disease and the increasing obesity of the population. This statement is in line with the recommendations of the National Cholesterol Education Program's Adult Treatment Panel that all Americans eat a diet containing 30 percent or less of energy from total fat, less than 300 mg of cholesterol per day, and 8-10 percent of energy from saturated fat (46). Data from the Third National Health and Nutrition Examination Survey indicate that the average population consumption levels are 34 percent of energy from total fat and 12 percent of energy from saturated fat (47).
The introductory paragraph indicates that the risk of certain cancers is linked to high fat intake. Although this relationship is confounded by the association between total fat intake and dietary energy, this statement reflects the scientific consensus that reducing total fat consumption is likely to reduce the incidence of certain cancers as well as atherosclerotic vascular disease (48).
The introductory paragraph notes that dietary saturated fat and cholesterol consumption are positively correlated with blood cholesterol levels, which in turn are linked to heart disease risk. The guideline, however, does not include a statement that blood (plasma) cholesterol concentration of less than 200 mg/dL is desirable (46). The committee feels that including a specific level of cholesterol is not appropriate for this document in order not to leave any implication that individuals with a value of less than 200 mg/dL can ignore all or part of this guideline. The guideline is not intended to deal with individual heart disease risk, which includes many other factors. The document does not now deal with these factors (such as family history of premature cardiovascular disease, low HDL cholesterol, hypertension, tobacco use, and diabetes) because to do so would diffuse the message about diet and tend to "medicalize" the guideline.
The document does not indicate that individuals vary in their blood cholesterol response to dietary saturated fat and cholesterol because there is no practical way to identify individuals who may be hyper- or hypo-responsive (49,50). Therefore, the committee thinks that such a statement will not be useful here.
The guideline now indicates that eating foods which contain less fat makes it easier to meet the guidelines for variety and grains, fruits, and vegetables, thereby tying this guide to others.
Upper boundary for fat intake
The guideline for total fat is "no more than 30 percent," rather than "30 percent or less." This change in wording is intended to downplay the implication "the lower the fat intake the better." The guideline also refers to Daily Values for total fat, saturated fat, and cholesterol. These numbers have been included for their educational value and also to facilitate application of the guideline.
Types and sources of fatty acids
The guideline now addresses the specific classes of fatty acids in fats: monounsaturated, polyunsaturated, omega-3 polyunsaturated, and trans. This explanatory material is important because many Americans are now aware of the relationship between types of fatty acid and blood cholesterol levels and health. The statement about trans fatty acids indicates that these components are less effective than (cis) monounsaturated or polyunsaturated fatty acids in reducing blood cholesterol, but it does not specifically compare trans fatty acids with saturated fatty acids because scientific data on this point are mixed (51). Mention of tropical oils has been deleted because these oils contribute little to total fat consumption (52).
The statement on dietary cholesterol has been expanded to indicate specific sources and includes a statement that reducing cholesterol, as well as saturated fat, consumption, reduces blood cholesterol concentrations. A comparison of the relative importance of dietary cholesterol and saturated fat has been omitted because quantitative comparisons are complex and difficult to justify. For example, some data indicate that the effect of saturated fat is determined in part by the amount of dietary cholesterol (53,54).
The committee also notes that national recommendations about cholesterol consumption recognize that dietary cholesterol may increase heart disease independent of its effect on plasma cholesterol concentrations (55). The guideline now refers to the Daily Value for cholesterol as 300 mg, a value which is consistent with recommendations of authoritative bodies (46). Although the average cholesterol consumption of Americans is now close to 300 mg for women and children (and only moderately lower than the average consumption for men), the committee believes that it is important to indicate that individuals should continue to limit dietary cholesterol.
Recommendations for children
Application of the guideline to infants and children is now specifically addressed. In keeping with recommendations by other authorities (56), the guideline is stated to apply only to children ages 2 years or older. For logical and practical reasons, the committee recommends gradual adoption of the guideline from age 2 to age 5 years, so that by the time children are in school, they should be consuming diets that follow the Dietary Guidelines. The committee considers this advice appropriate for health reasons and also to enable uniformity in directions for school lunch programs. The committee notes a recent study indicating no adverse effect among children of age 8-10 years of a diet that contained 28.5 percent of energy from total fat, 10 percent from saturated fat, and 90 mg cholesterol per 1,000 kcal (57).
Advice for today
In the "Advice for toda" section, the committee does not include a recommendation to have blood cholesterol checked because the guideline has been designed for individuals with low as well as elevated cholesterol concentrations. Existing Federal guidelines for measurement of blood cholesterol are available and these differ for children and adults (46,56). Greater emphasis is given than formerly to use of plant sources of protein-rich foods.
Choose a Diet Moderate in Sugars
The committee recommends a change in the wording of this guideline. The revised wording continues the consistent evolution of the Dietary Guidelines through their various revisions to encourage Americans to "focus on total diet in a more positive way" (58). In the committee's judgment the vast majority of scientific studies fail to show either significant detriment from consumption of sugars in the amounts generally consumed by Americans or significant benefit from reducing sugars consumption per se. This conclusion is consistent with the FDA's 1986 report "Evaluation of the Health Aspects of Sugars Contained in Carbohydrate Sweeteners" (59). Thus, the negative connotation of the word only in the 1990 title is considered inappropriate in the context of this guideline specifically and in the generally positive context of the recommended guidelines as a whole.
Sugars as a calorie source
The revised text omits the 1990 statement that sugars provide calories. This information now is included in the introduction under the heading "Foods Also Contain Energy," which reads in part, "carbohydrate and protein provide 4 calories per gram." Most Americans know that sugars are a source of calories, and the current "sugars" text includes such statements as "replace lost calories from fat with equal calories from carbohydrates" and "foods containing sugar substitutes, however, may not always be lower in calories than similar products that contain sugar," confirming that sugar-containing foods have calories.
Classification of carbohydrates
Sugars are carbohydrates by definition. The American Heritage Dictionary, 3rd edition, defines sugar as "any of a class of water-soluble crystalline carbohydrates, including sucrose and lactose, having a characteristically sweet taste . . ." and the Random House Dictionary of the English Language, 2nd unabridged edition, defines sugar as a "sweet, crystalline substance . . . a member of the same class of carbohydrates as lactose, glucose, or fructose." The fact that dietary carbohydrates also include the complex carbohydrates starch and fiber is noted in the text to differentiate sugars from the other classes of carbohydrates, which are discussed elsewhere in the Guidelines.
The 1995 text explains that, contrary to what many consumers believe, the body cannot distinguish between naturally occurring and added sugars. During the process of digestion, dietary complex carbohydrates are broken down to their component monosaccharides prior to absorption into the portal circulation. There is no evidence that the gut can distinguish between sugars which result from intestinal breakdown of complex carbohydrates or disaccharides originating within the intrinsic food matrix and the chemically identical, exogenous sugars added to food during processing or afterward.
Carbohydrates and weight maintenance
The revised text provides continuity with other guidelines by pointing out that to maintain weight when intake of fat is reduced, there needs to be an isocaloric substitution, mainly of carbohydrates, and that this carbohydrate should come principally from foods in the lower half of the Food Guide Pyramid. Additional sugars are recommended only for very active, high-energy-requiring consumers, and sugars should be used sparingly by people with low calorie needs or those trying to lose weight.
Sugars do not cause diabetes
The genetic defects for several uncommon forms of diabetes have now been identified. The precise etiologies of the most common forms of diabetes, Type I (insulin dependent) and Type II (non-insulin dependent) diabetes are not yet defined with certainty. Nonetheless, Type I diabetes is now known to be mediated by an autoimmune mechanism, and Type II diabetes has been linked to several genetic loci. There is no evidence that diabetes is caused by sugar intake. Nor is there evidence that the magnitude of sugar intake per se is related to the control of diabetic hyperglycemia. In its "Nutritional Recommendations and Principles for People with Diabetes Mellitus," the American Diabetes Association states that "for most of this century, the most widely held belief about dietary treatment of diabetes has been that 'simple' sugars should be avoided. . . . There is, however, very little scientific evidence that supports this assumption" (60,61).
In relation to Type II diabetes, the 1995 text adds a statement that correcting overweight requires reducing the total amount of food you eat and increasing the level of physical activity. This statement reinforces the recommendations on body weight maintenance and augmented physical activity presented elsewhere in the 1995 guideline and is entirely consistent with the American Diabetes Association recommendations on weight loss and exercise in overweight Type II diabetics (60,61).
Sugars do not cause hyperactivity
The committee recognizes that many Americans believe that sugar intake causes hyperactive behavior. Nevertheless, the preponderance of scientific data do not support the etiologic association (62-67). The committee thinks that a definitive statement that dietary sugars do not cause hyperactivity is both scientifically accurate and necessary to prevent unsound consumer practices that are the consequence of misinformation on this subject.
The role of sugar substitutes
The Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 1990, includes a short statement on use of sugar substitutes that was deleted from the published version of the Dietary Guidelines. The current committee agrees with the prior committee's recommendation that a statement on the role of sugar substitutes in weight control be incorporated into the guidelines because sugar substitutes are so commonly used by the population. The previous committee, however, "found evidence for the value of non-caloric sweeteners in weight reduction to be inconsistent" (59). In the text of the 1995 Dietary Guidelines, the present committee recognizes that foods containing sugar substitutes may not always be lower in calories than similar products that contain sugar and that the use of sugar substitutes without reducing the total calorie intake will not lead to weight loss. Because substitutes themselves do not provide significant calories, they may, however, be useful to people concerned about caloric intake. The committee believes that this cautious statement is now acceptable given the number of studies that support this contention (68-77).
Recommendation for fluoride
The revised text continues to support fluoride as an anti-caries agent with the new statement that an adequate intake of fluoride will help prevent tooth decay. Further, the guideline retains each of the recommendations about fluoridated toothpaste, dental consultation, and need for fluoride in the pediatric age group in the box accompanying the text. This is thought to be adequate given that the primary focus of the guideline is dietary sugar intake.
There are new data on the role of fluoride both in prevention of dental caries and in the etiology of dental fluorosis. Fluoride exerts its anti-caries effect primarily through a local effect at the tooth surface and not via a systemic route as previously believed (78). This observation diminishes the importance of and has led the committee to delete the 1990 statement that fluoride is "especially important for children whose unerupted teeth are forming and growing." In addition, given the importance of local fluoride action at the tooth surface, the committee highlights fluoridated water in the text. This recommendation is seen as particularly important for individuals who do not regularly use fluoridated dentifrices, a circumstance that applies particularly to low-income families (78). However, since excess ingested fluoride appears to be the principal cause of fluorosis of primary and secondary teeth during their developmental stages between 3 months and 7 years of age (78), the committee limits the text to "adequate" intake of fluoride and leaves in the accompanying box the recommendations for additional fluoride in dentifrice or other supplemental forms to a decision by the dental or medical caregiver.
Choose a Diet Moderate in Salt and Sodium
The suggested wording of this guideline: "Choose a diet moderate in salt and sodium," replaces the former "Use salt and sodium in moderation." This change is recommended to make it clear that foods -- processed, prepared, and preserved -- are the source of most dietary sodium. Use conveys the idea of using salt, as from the shaker, which is misleading, since the proportion of sodium or salt added at the discretion of the consumer is small (79,80). This wording is also consistent with that of other guidelines to "choose a diet."
Several changes are recommended in the text to clarify and amplify this guideline and to link it to the Food Guide Pyramid. A key objective of this revision is to shift the tenor of this guideline toward dietary advice and away from primary focus on hypertension. The role of sodium in high blood pressure continues to be a major rationale for this guideline, but with added emphasis on sodium as an essential nutrient that is substantially overconsumed by the American public in general.
The four principal messages associated with this guideline are presented below and supporting evidence is provided in a subsequent section:
* Sodium and salt are found in foods throughout the food groups.
This message, and the accompanying information that most salt consumed has been added to foods before they reach the consumer's table, are included in the 1990 Guidelines. The revised text notes that salt and sodium are added to foods not only to enhance taste but also because salt and sodium have many uses in food processing.
* Sodium is associated with high blood pressure.
This has been a central point of the sodium guideline. In this revision a statement linking sodium to normal blood pressure physiology has been added to help make the point that blood pressure risk occurs along a continuum. The prevalence of hypertension is not stated to avoid the impression that this guideline applies only to the third or quarter of the population whose blood pressure is over a certain threshold. The term diverse populations is used to describe the breadth of evidence supporting the sodium-blood pressure link. The revised text acknowledges the complexity and continuing uncertainty regarding interactions between sodium and other factors, including dietary factors addressed by other guidelines.
* Other factors affect blood pressure.
In contrast to the text for the 1990 guideline, which simply lists obesity as one in a list of other factors known to affect blood pressure, the revised text emphasizes the importance of weight control to reduce blood pressure risk in addition to moderation in sodium intake. The probable benefits of increased consumption of fruits and vegetables high in potassium, in conjunction with sodium reduction for high blood pressure risk reduction, are now mentioned in the text to acknowledge the large body of evidence linking a lower dietary sodium-potassium ratio to lower blood pressure. Based on the evidence reviewed, the committee considered it appropriate to express this advice in terms of fruits and vegetables, rather than potassium (a salt substitute, for example) as such. This advice reinforces the guideline to consume fruits and vegetables.
An informational statement about the possible association of calcium nutriture and high blood pressure has been included, and consumers are advised that moderating sodium consumption may have the benefit of reducing sodium-induced calcium depletion.
* Most Americans consume more salt than is needed.
The general over-consumption of sodium in the American population is noted here. The applicability of the recommendation to moderate sodium intake to the general population is also tied to the lack of probable harm associated with moderating sodium consumption for the healthy normal adult. To help with interpretation of the word moderate, this guideline refers to the level of 2,400 mg sodium (6 grams salt) listed as the Daily Value on the Nutrition Facts Label.
Advice for today
The "Advice for today" in the 1990 guideline places first emphasis on having blood pressure checked. There is now ample consumer guidance to this effect promulgated by health agencies. Because these are dietary guidelines, the revised text focuses on strategies for dietary sodium reduction, including the use of the Nutrition Facts Label. The availability of sodium content information and more uniform sodium-related health claims on food has evolved since 1990. These developments provide important new support for implementation advice. The "Advice for today" emphasizes the need to reduce the sodium obtained from frequently consumed foods throughout the Food Guide Pyramid (in contrast to focusing only on a few less frequently consumed high-salt foods). Accompanying boxed text gives specific behavioral strategies that have been identified as most effective in accomplishing dietarysodium reduction, touching upon several of the food groups and including strategies to stimulate increased availability of lower sodium food choices through retailers and restaurants. This behavioral approach is consistent with the Healthy People 2000 objectives.
Consistency with other recommendations
Reduction of sodium or salt or both in diets is recommended in both The Surgeon General's Report on Nutrition and Health and the National Research Council's (NRC) report Diet and Health (81,48). NRC suggests consuming less than 6 g salt per day; the Surgeon General's report presents no numeric goal. The Daily Value on the new food labels is 2,400 mg sodium per day, for both the 2,000 and 2,500 kcal intakes. This is equivalent to 6 g salt per day. The NRC's 10th edition of the Recommended Dietary Allowances gives 500 mg sodium per day as a safe minimum intake (82).
The Healthy People 2000 objectives quantify sodium reduction objectives in the form of targeted percentages of people who adhere to certain behaviors that are conducive to moderating sodium intake, preparing food without adding salt (target 65 percent), avoiding the use of salt at the table (target 80 percent), and regularly purchasing foods lower in sodium (target 40 percent) (83).
The committee received many comments on the sodium guideline and heard testimony from fully creditable health professionals who differed on the question of whether or not to retain this guideline. Detailed expert reports on the sodium and hypertension issue -- the NRC Diet and Health report (48), The Surgeon General's Report (81), and the report of a National Institutes of Health November 1989 workshop (84) were available to the 1990 committee. Additional support for the recommendation to moderate sodium intake has been published in the interim in the form of careful reviews of the most pertinent correlational (ecological) studies, observational studies, and clinical trials (85-87). In addition, a report describing the importance of both sodium reduction and weight reduction to prevent the development of high blood pressure was released by the National High Blood Pressure Education Program (88). Among the key evidence cited in this report are results of the first phase of a large, multi-center primary prevention trial -- the Trials of Hypertension Prevention (TOHP I). TOHP I results demonstrate that sodium reduction in individuals with initial blood pressures in the high normal range is feasible, is not associated with adverse effects, and is associated with statistically significant decreases in blood pressure over an 18-month period and of a sufficient magnitude to have important public health implications (89,90). Weight reduction is also effective in lowering blood pressure in TOHP I, with effects larger than those for sodium. Thus, although debate continues among scientists on the association between salt intake or sodium intake or both and the risk of developing high blood pressure (as opposed to the benefits for treatment of high blood pressure), the weight of overall evidence to date (including that which has become available in the interim since the 1990 Guidelines) still favors making a strong recommendation to moderate sodium intake.
The fact that high blood pressure affects only a subset of the population has been cited as a reason not to recommend reduced sodium intake for the general population. However, the new classification of blood pressure in the fifth report of the National High Blood Pressure Education Program's Joint National Committee, issued in 1993, characterizes blood pressure risk as a continuum with several stages, extending from normal blood pressure to high normal blood pressure to high blood pressure in stages of severity (91). This perspective on blood-pressure-related risk as a graded phenomenon beginning within the normotensive range, together with the evidence from prevention trials focusing on persons with high normal blood pressure, supports the applicability of the guideline to moderate sodium and salt intake to the general population. Furthermore, the inability to identify in advance individuals who are sensitive to the blood-pressure-raising effects of a high salt intake makes limiting the recommendation to a salt-sensitive subset of the population infeasible.
Studies of the relationship of substances other than salt and sodium to high blood pressure were discussed by the committee in order to determine how best to position the possible benefits of sodium reduction vis-ê-vis other blood pressure risk reduction strategies involving diet and to identify appropriate cross references to the other guidelines. Weight reduction is given more prominence in the text of the sodium guideline because evidence linking weight reduction to the primary prevention of hypertension is considered to be very strong (84,89). Blood-pressure- lowering effects reported for weight are larger than those for sodium but are considered additional to, rather than substitutes for, sodium effects; the latter, as reported in the literature, are probably underestimated (92). Moreover, in spite of the difficulty of achieving reduced sodium intake in the general population, the ability to achieve and maintain reduced sodium intake in the general population may be greater than the ability to achieve permanent weight reduction (89,90), particularly as the availability of reduced sodium foods increases through the cooperation of the food industry.
There is considerable evidence supporting the possible role of increased potassium intake in offsetting the effects of sodium on blood pressure (88). However, the total picture with respect to potassium is less convincing than that for sodium or weight because the potassium effect has been difficult to confirm in population-based clinical trials (88,93). Difficulty in confirming the potassium effect may stem from differences in the initial potassium intake of those being compared, in the form of potassium used (potassium chloride versus other forms), or because the effect of dietary potassium is relative to the sodium content of the diet. The recommended wording on this point in the 1995 guideline takes into account human studies suggesting that the form in which potassium occurs naturally in fruits and vegetables (salts of organic acids, ultimately, bicarbonate) does have a favorable effect on blood pressure (94).
Although it is clear that the calcium ion is involved in blood pressure regulation, available evidence for an independent role of dietary calcium intake in blood pressure control is less convincing than that for dietary sodium or potassium (95). To acknowledge the link between sodium, calcium, and blood pressure, the recommended wording draws attention to the possible role of calcium in this respect and to the effect of high sodium intake on calcium depletion (96).
Evidence of higher than recommended sodium intake among U.S. adults was updated by reference to dietary recall data reported from the 1988-91 National Health and Nutrition Examination Survey (NHANES III) for adults ages 20 years and older (97; unpublished data provided by the National Center for Health Statistics). Average sodium intake of adults ages 20 years and older is 3,400 mg per day overall in NHANES III: 4,063 mg for men and 2,769 mg for women. If the NHANES III estimate is increased by 15 percent to include discretionary salt, approximate sodium intakes for the total, male, and female adult populations are 3,900, 4,700, and 3,200 mg per day, respectively.
Information for assessing intakes
Information needed by the public to understand and use numerical goals for sodium or salt reduction is available for packaged foods that fall under the NLEA (98). However, such information is less available for catered and restaurant foods, which constitute a major portion of the food intake of most U.S. children and adults. The sodium content of foods is available to professionals in food composition tables, although the extent to which added salt is adequately or consistently estimated from these tables is uncertain.
Guidance for moderating salt and sodium in the diet has been included in the new food-labeling regulations and represents a major improvement in the possibility that consumers can identify the sodium content of the foods they purchase in supermarkets. Uniform definitions for serving sizes and for sodium content per serving have been implemented for sodium-content claims on food labels (for example, <140 mg per reference amount for a low-sodium food). In addition, foods making any of the health claims allowed by the NLEA are disqualified if they exceed certain specified limits. Including a reference to the 2,400 mg Daily Value for sodium intake stated on the Nutrition Facts Label provides a direct link between the Dietary Guidelines and the food label, promoting consistency of dietary guidance from these two sources.
If You Drink Alcoholic Beverages, Do So in Moderation
The committee recognizes that this guideline is unique among the Dietary Guidelines because the substance referred to is both a food -- that is, a calorie-rich beverage -- and a drug, and as the latter, is subject to abuse and can cause user dependency. The committee considered whether or not alcohol abuse and excess render this a public health issue that would be better approached somewhere other than in the Dietary Guidelines. Yet, alcoholic beverages are a regular part of the diet as well and, when used in moderation, may be safe and pleasurable. Because the absence of the guideline after its presence in the three previous editions would send a confusing message to the public, the committee concluded that the guideline should be retained with the same heading as in the 1990 version. Modest changes in the text are suggested.
The introductory statements refer to the widespread use of alcoholic beverages to enhance meal satisfaction throughout human history, and the introduction also refers specifically to the physiologic or drug effects of alcohol, including the capacity to alter judgment. As before, the early statements emphasize that dependency and excess can cause serious health problems.
The definition of moderation is retained from the 1990 edition, but the box defining moderation now appears earlier in the text. In this same box an additional statement is included that refers to the calories in alcoholic beverages (also referred to in the weight guidelines) and the possible contribution to weight gain.
Alcohol-disease risk relationships
The list of problems associated with heavy drinking has been expanded to include high blood pressure, stroke, heart disease, certain cancers, accidents, and violence. The concern in the 1990 edition that the beneficial effects of moderate intake on heart attack were offset by higher risk for hypertension and hemorrhagic stroke has not been supported by further studies in moderate drinkers where neutral or beneficial effects on risk of stroke or cerebrovascular disease have been recorded (99-104).
Those who should not drink
The list is similar to the 1990 edition but reordered to place children and adolescents at the top. The term adolescents is interpreted to include all people younger than the legal age of 21 years. Despite some studies showing no detrimental effects of low or moderate alcohol intake during pregnancy, the committee recommends continuation of the prudent advice that women who are pregnant or trying to conceive (that is, who might already be in the first few weeks after conception and before a determination as pregnant) should not drink, since an absolutely safe level of alcohol intake during early pregnancy has not been accepted. Like the 1990 committee, the current committee found insufficient evidence on which to base a recommendation on alcohol consumption during lactation.
Advice for today
The text expands the statement in the 1990 guidelines to emphasize the food use of alcoholic beverages rather than the social drug use. The section recognizes that consumption of alcohol with meals slows consumption and absorption of alcohol and notes that alcohol should not be consumed in situations where others might be put at risk.