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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary 1 Workshop Introduction1 Dr. John Suttie, chair of the workshop, welcomed participants on behalf of the Food and Nutrition Board (FNB), Institute of Medicine (IOM).2 He also gave a brief overview of the Dietary Reference Intakes (DRIs) and the format of the workshop. He then introduced Dr. Christine Taylor, Study Director and IOM Scholar, who described the current DRI framework and the issues that have been raised about the DRI development process. Dr. Suttie then invited Dr. Dennis Bier to offer his welcome as FNB chair. WELCOME AND OPENING REMARKS Presenter: John Suttie This workshop, through the generous support of the U.S. and Canadian governments, focuses on the process by which the DRIs were developed. It has been designed to identify lessons learned and to offer opportunities to discuss the ways in which the process might be enhanced. The development of reference values for nutrients has a long history. In 1994 the IOM, with the guidance of the FNB, undertook activities that resulted in major changes in how reference values were developed and The planning committee’s role was limited to planning the workshop, and the workshop summary has been prepared by the workshop rapporteur (with acknowledgment of the assistance of staff as appropriate) as a factual summary of what occurred at the workshop. 1 This chapter is an edited version of remarks presented by Drs. Suttie and Taylor at the workshop. 2 FNB, IOM hereafter jointly referred to as IOM.
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary presented, ultimately leading to the new DRIs. In many ways, these efforts considerably advanced the approach used to develop nutrient reference values. At that time we recognized that after some experience had been gained using this new approach, it would be worthwhile to pause and examine not only our successes, but the ways in which the approach could be improved. We are now at that point. Background for Workshop Discussions Reference values known in the United States as Recommended Dietary Allowances (RDAs) and in Canada as Recommended Nutrient Intakes (RNIs) were used through the 1990s. They were established primarily to set nutrition and health policy. In 1994, in response to important changes in the nutrition field as well as the recognition that for many nutrients the single RDA or RNI values did not meet the expanding needs for nutrient reference values, the IOM began an initiative to develop a new, broader set of values known as the DRIs. The U.S. and Canadian governments supported this initiative. More specifically, the DRIs as reference values now include upper levels of intake, where appropriate; incorporate chronic disease endpoints within the array of endpoints that may serve to establish adequate intake or upper intake levels; include “non-classical” nutrients; specifically highlight concepts of probability and risk for defining reference values; and are associated with publications intended to guide users of DRIs. The DRI component values are shown in Box 1-1. They are described and contained in six volumes published by the IOM between 1997 and 2005. To help users understand the DRIs, given the expansion of both the nutrient reference value approach and the types of reference values issued, two publications were created to provide general guidance for users, one focused on planning and the other on assessment. In 2006, the IOM issued Dietary Reference Intakes: The Essential Guide to Nutrient Requirements, which is available in English and French. Workshop Development A planning committee was convened early this year to assist the IOM in formulating the content and format of the workshop and in identifying candidates to serve as speakers, discussants, and panel members. The committee specified background materials to help participants prepare for the
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary BOX 1-1 Current Dietary Reference Intake (DRI) Components Estimated Average Requirement (EAR): Reflects the estimated median requirement and is particularly appropriate for applications related to planning and assessing intakes for groups of persons. Recommended Dietary Allowance (RDA): Derived from the EAR and covers the requirements for 97 percent of the population. Tolerable Upper Intake Level (UL): Highest average intake that is likely to pose no risk. Adequate Intake (AI): Used when an EAR/RDA cannot be developed; average intake level based on observed or experimental intakes. Acceptable Macronutrient Distribution Range (AMDR): An intake range for an energy source associated with reduced risk of chronic disease. workshop. These materials were available on the IOM website for review and comment prior to the workshop. As outlined on the agenda (see Appendix A), there are four major topic areas: (1) the conceptual framework for DRI development, (2) criteria for scientific decision making, (3) general guidance for users of DRIs, and (4) the future process for DRI development. In order to foster diverse discussions and include a range of perspectives, the workshop is organized around a series of presentations that are complemented by topic-designated discussions as well as broader panel discussions. Considerable time has been set aside for audience members to provide their views on the DRI process. In summary, this workshop offers a unique opportunity to consider the DRI process and raise issues important to its enhancement. Our intent is to have an open discussion that will prove useful as we consider the next steps for DRI development. Although the workshop is not charged with coming to closure on the issues raised and will not conclude with consensus recommendations, it should provide a useful spectrum of stakeholder comments on this important activity. OVERVIEW OF CURRENT DRI FRAMEWORK AND ISSUES RAISED Presenter: Christine Taylor A new approach to nutrient reference values was put in place in the mid-1990s to respond to the expanded uses of the values and to the newer
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary understandings of the role of nutrients. With 10 years of experience behind us, we now have the basis for considering how the approach has performed and whether enhancements or modifications are needed. This presentation sets the groundwork for the discussion by describing the current framework and identifying the issues raised. Outlining the Framework The original intent was for the DRI framework to be developed and “fleshed out” through the experience of developing the values. Therefore, the DRI framework does not exist in a single or codified document, but is gleaned from several sources. Principles for DRI development were articulated in a general way in the 1994 publication, How Should the Recommended Dietary Allowances Be Revised? (IOM, 1994). Further information can be found in the first DRI volume issued in 1997 (IOM, 1997), in the 1998 monograph that describes the approach for the upper levels of intake (IOM, 1998), and in the 2006 Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (IOM, 2006). Basic components of the DRI framework are shown in Figure 1-1.3 The initial component is the set of conceptual underpinnings that may be referred to as first principles. It includes the task of problem formulation, a dialogue to ensure common understanding, and clarification of the reasons for the activity. Next is what can be referred to as a road map—principles and criteria for the study committees to use as they develop nutrient reference values. Following these activities is general guidance for users to outline appropriate strategies for applying the reference values. Some important DRI-related activities are outside the scope of the workshop and should be addressed separately. One is the critical set of issues surrounding the research needed to elucidate the basic physiology, metabolism, and homeostatic mechanisms—in essence, the data that provide the raw materials for DRI development. Second are the science and considerations needed to allow application of the DRIs under specific situations that require in-depth study and consideration beyond that which can be provided in general guidance to users (e.g., the use of the DRIs for nutrition labeling or in developing food assistance programs under U.S. federal regulations). The workshop agenda (Appendix A)—and hence the workshop presentations and discussions—moves sequentially through the framework as outlined. Session 1 focuses on the underpinnings and then addresses general road map considerations. Session 2 continues with the road map, focusing 3 The workshop planning committee used a more complex schematic of the DRI process (see Appendix D) in its deliberations.
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary FIGURE 1-1 DRI framework schematic. Framework components that are the subject of the workshop are identified in the box; other important activities are identified outside the box. (See also Appendix D.) NOTE: DRIs = Dietary Reference Intakes. on six topics. Session 3 explores the general guidance for users. Session 4 considers the future process. Although the activities in the workshop are not strictly linear and a number of issues are crosscutting and iterative, the organization of the workshop provides a reasonable way to manage and focus the needed discussions. Conceptual Underpinnings The conceptual underpinnings have the following two major components: Purpose of the DRIs (i.e., the goals and guiding principles) Setup of DRIs (i.e., the kinds of values to be expressed, the types of endpoints that are appropriate, and the nature of the nutrient substances for DRI development) DRIs were identified in 1994 as standards to serve as a goal for good nutrition. They were to focus on groups of healthy persons, but the desir-
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary ability of exploring ways to evaluate individuals was highlighted. From 1997 to 2006, the DRIs were identified as serving the purpose of planning and assessing diets for healthy populations and other purposes. Question: Does the development of standards for planning and assessing healthy groups and individuals remain the general purpose of the DRIs? Turning to the DRI setup, as early as 1989 it was recognized that the RDA value alone was not sufficient to meet all the reference value needs. In 1994, DRIs were foreshadowed as a set of values that would include more than an RDA—specifically, an estimation of a median or average requirement as well as an indication of an upper level of intake. These became the Estimated Average Requirement (EAR) and the tolerable upper intake level (UL). Activities in 1997 and beyond added Adequate Intakes (AIs) and the Acceptable Macronutrient Distribution Range (AMDR). Questions: Do the EAR, RDA, and UL continue to be desirable values? Is the AI still useful and needed, and should it be better defined? Does the AMDR pave the way to considering macronutrients using a different approach? Also relevant to the DRI setup is the type of endpoints that are appropriate. The existing framework addresses two types: endpoints to ensure adequacy and endpoints to avoid excess, each of which include chronic and non-chronic disease endpoints. Most DRIs, whether focused on adequacy or on upper levels, are based on non-chronic disease endpoints. The incorporation of chronic disease endpoints has been challenging. In addition, some have raised the question about the desirability of providing values based on more than one endpoint for specific age/gender groups. Although different endpoints for different age/gender and life stage groups are now used as appropriate, a single endpoint, rather than multiple endpoints, is selected for each group. Questions: Should we continue to include reduction of chronic disease risk as an endpoint option? Should we explore the option of issuing DRI values for multiple endpoints for a single group, allowing users to select their preferred endpoint? Finally, the question arises about nutrient substances appropriate for DRI development. Historically, these substances have been essential or so-called classic nutrients. More recently, compounds found naturally in foods have been included—usually those with potential risks or possible benefits to health, such as fiber, cholesterol, and saturated fat.
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary Questions: Should the focus of the DRIs continue to expand beyond classic nutrients? Is a modified DRI approach needed to address macronutrients and nonessential nutrient substances? Road Map In essence, the road map focuses on the steps of DRI development. In planning the workshop, we learned that much work needs to be done to provide a road map for the study committees. However, a set of initial questions needs to be addressed. Initial Questions: Can we provide more specific guidance on scientific decision making to help study committees clarify the concepts and tasks and to promote consistency across study committees? Can we provide guidance to study committees on the use of scientific judgment in the face of limited data that would allow the derivation of the judgment to be more transparent and better documented? Other issues relate to the general process for developing DRIs including the ability to specify an organizing scheme and the role of systematic evidence-based reviews. Process Questions: What is the role of systematic evidence-based reviews in DRI development? Can an organizing scheme for DRI development be specified? An apparent organizing scheme is outlined in Figure 1-2. Study committees first review the data and develop the DRI values. There is some concern as to whether study committees consistently attend to the useful next step of reviewing the exposure (or intake) assessment for the population of interest, placing the DRI values in context, and characterizing the risk of inadequate or excessive intakes. Given this concern, the discussions during the workshop are expected to focus on the agreed-upon general steps for DRI development and on enhancing the risk characterization and related “contextual discussions,” particularly as they relate to clarifying uncertainty and precision of the value, and comparing the values with the current estimated intake. Another focus is increased efforts to enhance the formal collaboration of the steps for determining reference values for adequacy and for determining upper levels of intake. Discussions about specific road map tasks related to scientific decision making can be used to identify the best questions about these important
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary activities and the best approaches for developing better criteria for use by study committees. These road map tasks include the approach for selecting endpoints, notably selection criteria and consistency of the approach used; available methodologies for approximating dose–response relationships in the face of limited data, given the critical nature of such data; strategies for extrapolation, scaling, and interpolation of values from a particular age/gender group to an unstudied group; adjusting for data uncertainty, including the possibility of a specific rationale and criteria; strengths and limitations of dietary intake estimates as they may impact risk characterization; and important areas to be monitored during the process of DRI development as they relate to environmental, genomic, and physiological factors. FIGURE 1-2 Basic steps in DRI development. NOTE: DRI = Dietary Reference Intake.
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The Development of DRIs 1994–2004: Lessons Learned and New Challenges - Workshop Summary General Guidance for Users Issues raised concerning general guidance for users relate primarily to the publications on applications in dietary assessment and planning (IOM, 2000a, 2003a). The guidance outlines a general approach for using the various DRI values and is linked to the existing purpose of DRIs: planning and assessment for groups and individuals. It is important to distinguish between “uses” as they relate generally to the purpose of DRIs and “uses” as they relate to general applications of DRIs in real-world settings when dietary planning and assessment are taking place. Examples of issues related to “uses” as they relate to the purpose of DRIs—and thus earmarked for discussion as components of the conceptual underpinnings—include the uncertainty surrounding or precision of the reference values, and how appropriate those values are for use with diseased populations. Diverse issues have been raised about guidance for users, many of which will require in-depth and focused discussions. Questions: How should AIs be used to address planning and assessing, especially within the context of the total diet? Can clarification be provided on the differences between groups and individuals and between applications for small groups and large groups? What practical guidance and tools can be used to assist practitioners? Looking to the Future A pivotal aspect of discussion about the DRI development process is how it will work in the future. Key topics to be addressed include ways to enhance transparency of the decision-making process; criteria and strategies for updating and reviewing the DRIs; how to determine what and when “new” nutrient substances are appropriate for DRI development; options for stakeholder input within the DRI process; and issues that may emerge in the future. With this framework as a basis, we hope the rationale for the questions posed will be clear and the workshop discussions will be well grounded. Thank you in advance for what we are certain will be a rich conversation among a diverse set of experts and stakeholders.
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