Harmonization of Approaches to Nutrient Reference Values Applications to Young Children and Women of Reproductive Age (2018) / Chapter Skim
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In response to the recognized need for a more comprehensive approach to developing nutrient intake recommendations, the United Kingdom, the European Union, and the United States jointly with Canada developed dietary reference values (DRVs) and Dietary Reference Intakes (DRIs)
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THE COMMITTEE'S TASK The need for guidance and recommendations about methodological approaches, as well as their potential for application to an international process for the development of NRVs, and particularly for young children and women of reproductive age, prompted the Bill & Melinda Gates Foundation to ask the National Academies of Sciences, Engineering, and Medicine to hold a workshop, convene a consensus committee to examine these issues, and make recommendations for a unified approach to developing NRVs that would be acceptable globally. To set the stage for the consensus committee's work, a workshop, Global Harmonization of Methodological Approaches to Nutrient Intake Recommendations, was convened at the United Nations' Food and Agriculture Organization (FAO)
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KEY FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS The purpose of developing NRVs is to assure that, if met, the majority of a generally healthy population will have sufficient intake levels to prevent nutrient deficiency disease and avoid adverse effects of excessive intake. When applicable, reference values may also be determined to reduce risk of chronic disease.
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Nutrient reference expert panels should make two values their priority: specifically, the population average require ment (AR) and safe upper levels of intake (ULs)
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Recommendation 4. When deriving nutrient reference values, countries or regions should look at existing values derived by expert panels and determine whether to accept, update, or adapt them to their context, if possible.
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derive the two key reference values, the AR and UL. ASSESSMENT OF EXEMPLAR NUTRIENTS The committee applied the framework to two population groups, young children and women of reproductive age, and used case analyses of three exemplar nutrients -- zinc, iron, and folate -- to examine the feasibility of its recommendations for harmonizing the methodological approaches to
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In contrast, supplements have been shown to cause prompt in creases in plasma zinc concentrations irrespective of dietary intake. Although linear growth has been recommended as a functional indicator of zinc status, because low height- or length-for-age has been shown to be responsive to supplemental zinc, as with plasma zinc concentrations, the response to additional dietary zinc is not as strong as the response to similar doses of supplemental zinc.
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• Because the physiological requirements and ARs for young chil dren and women of reproductive age that have been made by the authoritative bodies reviewed in this report are very similar, efforts should be made to consolidate these estimates globally. However, there may still be a need to set national RIs based on the dietary zinc source (i.e., bioavailability)
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If the mean iron intake is below the AR, then evidence of iron deficiency must be supported by measures of iron status. However, because dietary iron exists in two forms, measuring dietary intake is difficult owing to limited information on heme iron in food composition databases.
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• There are challenges to setting an iron UL, but such a value is es sential for evaluating the safety of food iron fortification and other public health programs. Proposed Solutions Although the factorial method has been universally adopted by authoritative bodies globally, there remains wide variation in NRVs determined for women of reproductive age, mainly because of different calculations used to transform physiological requirements into dietary intakes.
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While cooking techniques affect the amount of folate required from food sources, it does not affect physiological requirements. • As with food preparation, while folic acid fortification of staple and other foods does not affect the physiological requirement for folate, it does affect the amount required from food sources.
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There are no major deterrents to using existing reference values published by authoritative bodies or to modifying them to the local context. However, the committee identified a number of data gaps for deriving new, country-specific folate NRVs: • The lack of validated data on the folate content of foods in low and middle-income countries, especially cooked foods; • Increasing, but still insufficient evidence for population prevalence of polymorphisms and their effect on folate requirements;
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CONCLUSION AND NEXT STEPS From its assessment of the current process for deriving NRVs, the application of new tools to this process, and its three nutrient case analyses, the committee concluded that it is feasible to harmonize the process to derive reference values globally. Recommendation 6.
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An important next step is for the key enablers of harmonizing NRVs to develop a tool kit that participants, particularly those from lowand middle-income countries, can use to guide the development of methodological approaches to deriving NRVs for their populations. This report's intent is to provide the guidance needed as global stakeholders consider moving toward the subsequent steps of implementation, dissemination, and evaluation.
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