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Introduction

The science of human nutrition stands at a pivotal point in its development. We now understand not only that nutrients are essential for growth and development and health maintenance, but also that some play a role in the reduction of risk of chronic disease. We have also come to understand that some nutrients function as hormones and others as gene regulators. A time may come when recommendations about what constitutes a health-promoting diet could be tailored to an individual 's genetic predisposition to disease. However, until we have more complete knowledge of genetic variability in nutrient needs for health promotion and disease prevention, we must continue to rely on population-based approaches. One such approach is to develop recommendations for nutrient intakes that are designed to cover individual variations in requirements and that also provide a margin of safety above minimal requirements to prevent deficiency diseases. This is the approach traditionally taken in establishing Recommended Dietary Allowances (RDAs).

Since the RDAs were first published in 1941, their application has expanded markedly. They serve important functions in a variety of nutrition-related activities that professionals in government, industry, academia, and the health services have undertaken. The many uses of the RDAs are summarized in Table 1. For example, the allowances are meant to serve as guides for procuring food supplies for groups of healthy persons, as the basis for planning meals for groups, as a reference point for evaluating the dietary intake of population subgroups, and as a component of food and nutrition education programs. Since 1972, the RDAs have functioned as the reference point for the nutritional labeling of foods and dietary supplements.



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HOW SHOULD THE RECOMMENDED DIETARY ALLOWANCES BE REVISED? 1 Introduction The science of human nutrition stands at a pivotal point in its development. We now understand not only that nutrients are essential for growth and development and health maintenance, but also that some play a role in the reduction of risk of chronic disease. We have also come to understand that some nutrients function as hormones and others as gene regulators. A time may come when recommendations about what constitutes a health-promoting diet could be tailored to an individual 's genetic predisposition to disease. However, until we have more complete knowledge of genetic variability in nutrient needs for health promotion and disease prevention, we must continue to rely on population-based approaches. One such approach is to develop recommendations for nutrient intakes that are designed to cover individual variations in requirements and that also provide a margin of safety above minimal requirements to prevent deficiency diseases. This is the approach traditionally taken in establishing Recommended Dietary Allowances (RDAs). Since the RDAs were first published in 1941, their application has expanded markedly. They serve important functions in a variety of nutrition-related activities that professionals in government, industry, academia, and the health services have undertaken. The many uses of the RDAs are summarized in Table 1. For example, the allowances are meant to serve as guides for procuring food supplies for groups of healthy persons, as the basis for planning meals for groups, as a reference point for evaluating the dietary intake of population subgroups, and as a component of food and nutrition education programs. Since 1972, the RDAs have functioned as the reference point for the nutritional labeling of foods and dietary supplements.

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HOW SHOULD THE RECOMMENDED DIETARY ALLOWANCES BE REVISED? TABLE 1. Uses of the RDAs USE EXAMPLES COMMENTS ON THE USE OF RDAs Food planning and procurement Use to develop plans for feeding groups of healthy people Use as an appropriate nutrient standard for a period of at least a week, but also use as one of many food planning criteria; should be adjusted as group varies from RDA reference individual   Use for food purchasing, cost control, and budgeting Use as an appropriate nutrient standard with knowledge of such factors as food composition, availability, acceptability, and storage changes and losses Food programs Serve as a basis for the nutritional goal for feeding programs Use as a standard for nutritional quality of meals along with other food selection criteria   Provide the nutritional standard for the Thrifty Food Plan, the basis for allotments in the Food Stamp Program Use as a guideline along with other food selection criteria   Provide nutritional guidelines for food distribution programs Use as a standard for nutritional quality of food packages Evaluating dietary survey data Evaluate dietary intake of individuals Use as a standard for evaluating dietary status, but not for evaluating individual nutritional status   Evaluate household food use Use as a benchmark to compare households and to identify nutrient shortfalls   Evaluate national food supply (food disappearance data) Use only as a benchmark for comparison over time and to identify nutrient shortfalls Guides for food selection Develop and evaluate food guides and family food plans Use along with other food selection criteria Food and nutrition information and education Provide guidelines for obtaining nutritious diets Use as a point of reference; becomes more useful to consumers when translated into food selection goals

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HOW SHOULD THE RECOMMENDED DIETARY ALLOWANCES BE REVISED?   Use as a basis for educators to discuss individuals' nutrient needs Use in combination with information in the text accompanying the RDA table and with recognition that the RDAs are for reference individuals   Evaluate an individual's diet as a basis for recommending specific changes in food patterns and/or dietary supplements Use to identify nutrient shortfalls and as a tool to assess nutrient contribution of diet; do not use in prescriptive manner Food labeling Provide basis for nutritional labeling of foods Use as a basis for labeling standards (U.S. RDA); such standards should not be used to determine nutritional intake of individuals or groups Food fortification Serve as a guide for fortification for general population Use as a guide, but such other factors as food consumption patterns and contribution to the total diet also must be considered Developing new or modified food products Provide guidance in establishing nutritional levels for new food products Use in combination with information or probable products; use within the context of the total diet Clinical dietetics Develop therapeutic diet manuals Use to assess the nutritional quality of modified diets   Plan modified diets Use as a starting point along with information on the patient's nutritional status and individual needs   Counsel patients requiring modified diets Use as one basis for advice on food selection   Plan menus and food served in institutions for the developmentally disabled Use as a starting point, but modify for individual's developmental status and body size Nutrient supplements and special dietary foods Use as a basis to formulate supplements and special dietary foods Use as a basis in developing infant formulas and other oral supplements or foods, but also consider nutrient bioavailability and nutrient balance; cannot be used as the only guide for parenteral feeding products SOURCE: Adapted from Uses of the Recommended Dietary Allowances, unpublished manuscript, 1983.

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HOW SHOULD THE RECOMMENDED DIETARY ALLOWANCES BE REVISED? Although some nutrition professionals question the need for RDAs, most would agree that some type of nutrient-based standard is necessary. The RDAs have become so integral to food and nutrition policy in the United States that it is difficult to conceive of planning a food program or changing a nutrition policy without considering how either would affect the population's dietary intakes expressed in relation to the RDAs. Since 1941, the Food and Nutrition Board (FNB) has issued reports periodically providing “standards to serve as a goal for good nutrition. ” Successive editions of the Recommended Dietary Allowances provided intakes of specific levels of several essential nutrients by age group, sex, and as appropriate, physiological state. These levels are judged on the basis of available scientific evidence to meet the known nutritional needs of practically all healthy persons in the United States. Concurrent with the expansion of knowledge of the biochemical function of specific nutrients, knowledge of how diet influences the risk of chronic diseases has also increased. In 1989, the FNB released Diet and Health, a major review of the evidence relating dietary patterns, food consumption, and nutrient intake to the development of chronic diseases that are the primary causes of morbidity and mortality in the United States (NRC, 1989a). These include atherosclerotic cardiovascular diseases, hypertension, obesity and eating disorders, cancers, osteoporosis, diabetes mellitus, hepatobiliary disease, and dental caries. Topics covered in the report encompassed total macronutrient intake, energy expenditure and net energy stores, fats and other lipids, proteins, carbohydrates, dietary fiber, fat-soluble vitamins, water-soluble vitamins, essential minerals and trace elements, electrolytes, alcohol, coffee, tea, and dietary supplements. The FNB now faces the challenge of whether to bring together the concepts of a health-promoting diet to reduce the risk of chronic disease and the nutrient-specific concepts underlying the RDAs. In 1992, the FNB began the first phase of what it envisioned to be a two-phase project leading to an eleventh edition of the RDAs. In phase I, the FNB would determine if there were compelling reasons to revise the tenth edition; if the answer was yes, it would begin phase II—develop an approach, strategy, and scope of work for the study. The task begun by the FNB in phase I was to determine whether or not the RDAs needed revision. Phase I included the symposium, public hearing, and FNB meeting in June 1993 from which it was clear that the community believed that the time had come to revise the RDAs. This concept paper represents the end of phase I and moves the FNB into phase II. Phase II would require several years and an intense level of activity that would culminate in the publication of an eleventh edition of the RDAs and possibly several derivative reports.

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HOW SHOULD THE RECOMMENDED DIETARY ALLOWANCES BE REVISED? The FNB held a national conference, consisting of a symposium and a public hearing, in June 1993 to explore several key issues related to the future of the RDAs. Members of regulatory and other federal agencies discussed their experiences in applying the RDAs in different policy situations and identified factors limiting their usefulness. Nutrition and medical experts described new evidence attained since publication of the tenth edition that would support a change from the present values or a reexamination of the data base. Also discussed was incorporating concepts related to reducing the risk of chronic disease in the development of nutrient-specific allowances. Some speakers offered alternative formats for presenting RDAs. Following the conference, the FNB concluded that further discussion of these issues was needed. Although there is substantial support for the revision of the current RDAs, the approach to be taken in this revision needs further development. The FNB members believe that they must develop, discuss, and disseminate new concepts of the RDAs with the scientific and professional communities to gain widespread support and agreement on an approach before a new RDA committee is convened. Therefore, this publication was prepared to summarize the issues discussed during the conference and to propose an approach to reconceptualizing the RDAs.

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