Traditionally, recommended intake levels for nutrients and other dietary components were designed primarily to prevent nutrient deficiency diseases in a population. Furthermore, although used for individual counseling, the recommended dietary allowances (RDAs) were not designed for dietary planning and assessment of the dietary needs of individuals and they did not take into consideration chronic disease endpoints (NASEM, 2018). However, with increasing globalization of information and the identification of a variety of factors specific to different population subgroups that influence their nutritional needs, there was recognition of the need for a more encompassing approach to setting nutrient reference values (NRVs). To address these issues, the United Kingdom (UK) Committee on Medical Aspects of Food and Nutrition Policy began the process by defining a lower reference intake and an average requirement (see Chapter 2, Table 2-1). A reference nutrient intake that meets the needs of practically all healthy individuals was retained (UK Department of Health, 1991).
Subsequently, the Food and Nutrition Board organized a symposium under the auspices of the Institute of Medicine and published How Should the Recommended Dietary Allowances Be Revised? (IOM, 1994). The symposium brought together stakeholders from government, academia, industry, and clinical dietetic practice to discuss issues that should be addressed in order to move the RDA process forward. The discussion included the question of whether there was sufficient evidence to change the existing single value—the RDA—to include other values or intake ranges. The
symposium participants recognized the need to use a statistical approach to define the average requirement and recommended intakes. The need for safe upper intake levels for nutrients was identified. Subsequently, when NRVs were developed, there was recognition of the need to understand the application of the values to facilitate planning and assessment of diets for individuals and populations (IOM, 2003). NRVs and intake ranges are discussed in more detail in Chapter 2 (see Box 2-1).
These activities galvanized action in the United States and Canada to move toward a more uniform and comprehensive approach to setting nutrient intake recommendations. The result was the Dietary Reference Intakes (DRIs) produced jointly by the United States and Canada. Other authoritative bodies in the following countries then developed similar approaches: the European Union; China; Korea and Southeast Asia; Germany, Austria, and Switzerland; Australia and New Zealand; and Mexico.
With adoption of a methodological structure for developing NRVs, there was recognition of an opportunity for global harmonization of the methods and approaches used (see Box 1-1). In an international meeting held in Florence, Italy, the importance of methodological harmonization was recognized and guidelines for its implementation were proposed (King and Garza, 2007).
While there is general consistency between many developed countries, including the United States, Canada, and European countries, in the methodological approach to derive NRVs, particularly the average requirement (AR) and upper level (UL), there remains considerable inconsistency across other national and international bodies. This is particularly true in the developing world in the approaches used to derive NRVs for specific population subgroups. Few review processes are in place to ensure that NRVs remain current and relevant to those population subgroups. Furthermore, the scientific resources needed to review and revise NRVs for specific population subgroups varies widely across countries and in some cases may not exist, resulting in gaps and inconsistencies in nutrition policy goals, guidelines, and recommendations. The experiences and the lessons learned from those countries that have worked toward harmonization of methodologies for deriving NRVs provide a rich backdrop for dialogue about the possibilities and limitations of standardizing approaches to setting such reference values across countries and globally, particularly among low- and middle-income countries.
The need for guidance and recommendations on methodological approaches and their potential for application to an international process for the development of NRVs, as well as the methodological approaches to recommended intakes across population subgroups (particularly young children and women of reproductive age), prompted the Bill & Melinda Gates Foundation to ask the National Academies of Sciences, Engineering, and Medicine (the National Academies) to examine this issue and make recommendations for a more unified approach that would be acceptable globally.
A two-part process was undertaken. First, a planning committee was convened to plan an international workshop to explore questions about frameworks used in the development of nutrient intake recommendations, the status of intake recommendations globally, and experiences and expertise relevant to the international harmonization of methodological approaches to setting intake standards. The workshop, Global Harmonization of Methodological Approaches to Nutrient Intake Recommendations, held at the Food and Agriculture Organization (FAO) headquarters in Rome, Italy, provided a venue for dialogue and discussion about the experiences, both positive and negative, of current approaches to nutrient intake recommendations (NASEM, 2018).
The workshop (see Appendix B for the workshop agenda) served as a foundation for a discussion of the evidence by an ad hoc consensus committee to explore the experiences of different countries or authoritative bodies’ current approaches to developing nutrient intake recommendations; examine the current evidence, including the strengths and weaknesses in
current and proposed methodological approaches to setting nutrient intake recommendations across developed and developing countries; assess the feasibility of harmonizing identified methodologies using a selected nutrient test case; and offer recommendations and action steps to facilitate the harmonization and standardization of methodological approaches for setting nutrient-based intake recommendations on a global scale (see Box 1-2). The committee was not asked to address the actual harmonization of NRVs, only the approaches used to derive them. Nor was the committee asked to determine how to implement its recommendations for a harmonized approach to deriving NRVs, although it did consider possible next steps toward implementation (see Chapter 5).
In its task, the committee was asked to consider the implications of harmonizing methodological approaches to deriving NRVs for a specific population subset, young children and women of reproductive age. While “young children” is defined in this report as birth to 5 years of age, the committee’s analyses of exemplar nutrients (see Chapter 4) include consideration of other age categories in some instances, depending on data availability or age ranges used to set NRVs (e.g., see Chapter 4, Table 4-3).
In response to the Gates Foundation request, the Health and Medicine Division of the National Academies established a committee with expertise in nutrition science, DRIs, dietary patterns, epidemiology, study design
and methodology, statistics or biostatistics, and international nutrition standards. The committee attended the international workshop Global Harmonization of Methodological Approaches to Nutrient Intake Recommendations held in Rome, Italy, at the headquarters of FAO of the United Nations on September 21–22, 2017 (see Appendix B). The committee then met in closed session and by conference calls to deliberate on its task. The committee’s findings, conclusions, and recommendations are derived from its assessment of relevant evidence.
This report reviews and evaluates the evidence for global harmonization of methodological approaches to deriving NRVs with a specific focus on young children and women of reproductive age. The report is organized into five chapters. Chapter 1 describes the background for the study and the statement of task. Chapter 2 describes the concepts underpinning the development of NRVs. Chapter 3 examines the key steps in the process for deriving reference values. Chapter 4 applies a framework to three nutrient case analyses to examine the feasibility of harmonizing the methodological approach. Although Chapter 4 focuses on three specific nutrients (zinc, iron, folate), the committee uses relevant examples of other nutrients in other sections of the report. Chapter 5 proposes a way forward with future directions to achieve harmonization and examines current data and research gaps.
Appendix A presents a glossary of terms used in the report. Appendix B presents the agenda for the workshop held in Rome and an additional open session held by the committee. Appendix C describes the Appraisal of Guidelines for Research and Evaluation II (AGREE II) instrument. Appendix D presents a table of tools and methods to evaluate the risk of bias in an individual study. Appendix E shows a compilation of the scaling methods used to extrapolate from the reference values of one age group to another. Appendix F contains the European Food Safety Authority’s Scientific Opinion on Dietary Reference Values for Protein: Growth Factors for Children Age 6 Months to 17 Years. Appendix G contains the committee members’ biographical sketches.
IOM (Institute of Medicine). 1994. How should the recommended dietary allowances be revised? Washington, DC: National Academy Press. https://doi.org/10.17226/9194.
IOM. 2003. Dietary Reference Intakes: Applications in dietary planning. Washington, DC: The National Academies Press. https://doi.org/10.17226/10609.
King, J. C., and C. Garza. 2007. Harmonization of nutrient intake values. Food and Nutrition Bulletin 28(Suppl. 1):S3-S12.
NASEM (National Academies of Sciences, Engineering, and Medicine). 2018. Global harmonization of methodological approaches to nutrient intake recommendations: Proceedings of a workshop. Washington, DC: The National Academies Press. https://doi.org/10.17226/25023.
UK (United Kingdom) Department of Health. 1991. Dietary reference values for food energy and nutrients in the United Kingdom (Report on health and social subjects; 41). London, UK: Her Majesty’s Stationery Office. https://www.nutrition.org.uk/attachments/article/234/Nutrition%20Requirements_Revised%20Oct%202016.pdf (accessed March 4, 2018).