As elaborated in the earlier chapters in this report, the concept for a structure to harmonize the methodologies for establishing nutrient reference values (NRVs) began in the 1990s, with discussions among experts from the United States, Canada, and the United Kingdom. This led to convening an international stakeholder group to lay out the components of a universally applicable organizing framework (King and Garza, 2007). In the interim, new tools have been developed that were not available or used previously. These include systematic reviews, larger and more accessible databases, information on factors affecting culture- and context-specific food choices and dietary patterns, new modeling techniques (e.g., new tools for assessing risk of bias), and new metabolic biomarkers of nutritional status.
These tools have enabled more transparent, scientifically rigorous, and efficient approaches that enhance the feasibility of developing NRVs across broader, more diverse population subgroups. Building on this background, the committee examined the strengths and weaknesses of current approaches, evaluated their application to two high-risk population subgroups, young children (birth through 5 years of age) and women of reproductive age, and assessed the feasibility of harmonizing methodologies to derive NRVs on a global scale. While it was beyond the committee’s scope to determine how to implement its recommendations for a harmonized approach to deriving NRVs, it did consider possible next steps toward implementation. This final chapter reiterates the advantages of the harmonization of approaches used to derive NRVs; considers options and strategies to facilitate harmonization; and identifies data gaps that need to be filled.
Building on the work of King and Garza (2007), the committee identified several additional reasons to harmonize the approach to deriving NRVs. First, a harmonized approach will prioritize the derivation of the average requirements (ARs) and tolerable upper intake level (UL). Currently many countries and/or organizations do not appreciate that deriving values for ARs and ULs is a greater priority than recommended intakes (RIs). It is not possible to derive valid estimates of the prevalence of inadequate nutrient intakes without first deriving the AR and UL. Furthermore, the AR and UL are necessary values for estimating nutrient intake gaps that require agricultural, fortification, or supplementation programs, as well as being necessary for evaluating the effectiveness and safety of policies to fill these gaps.
In addition, the high cost of the process of deriving NRVs means that nutrient intake recommendations are updated infrequently. It will be much more cost-effective to use a harmonized approach than to have different countries or organizations developing their own. The cost of conducting systematic reviews alone is prohibitive even for global organizations, such as the World Health Organization (WHO) and the United Nations’ Food and Agriculture Organization (FAO) and wealthier countries. For example, it was suggested at the Global Harmonization workshop that a central repository for systematic reviews and other data sources be established that is accessible to all countries. Another advantage of harmonization is that it will enable comparison of the adequacy of nutrient intakes around the world. Finally, the increasing globalization of trade in processed and fortified foods means that labeling and nutrient content information on foods must be as consistent and understandable as possible; a harmonized approach will help to achieve consistency.
There has been relatively little implementation of the organizing framework for harmonizing NRVs proposed in the King and Garza (2007) report. Moving forward will require overcoming the barriers to implementation that clearly exist and that were discussed at the Global Harmonization workshop (NASEM, 2018). The committee identified two sets of options for overcoming these barriers: (1) increasing access to systematic reviews and other data sources for low- and middle-income countries; and (2) sharing scientific expertise and improving consistency between trade partners on nutrient content information.
Increasing Access to Data
One option for increasing access to data is to create data repositories and make them publicly and globally available. Such repositories could include systematic reviews of existing literature on nutrients; food composition data; or nutrient bioavailability data and algorithms. Some databases may need to include locally or regionally specific data. While making the repositories available online would increase access for low- and middle-income countries, finding a host institution to accrue and update the information may be a challenge. An exemplar model might be the Vitamin and Mineral Nutrition Information System hosted by WHO.1 In addition, by coupling repositories with software packages that include algorithms or models that make bioavailability corrections that use AR and UL data, low- and middle-income countries would be able to use this data to estimate the prevalence of inadequate and excessive intakes in specific population subgroups.
Sharing Scientific Expertise
Scientific expertise is not always available to cover reviews for all nutrients or population subgroups (e.g., infants) in a country. A manual with training modules and other supportive information could be of great value in training new scientists and for guiding agencies who are interested in working on nutrient requirement recommendations. The modules could be made available online and implemented with the support of national nutrition societies, such as the International Union of Nutritional Sciences (IUNS). Such a manual could become an important mechanism for communicating information with a majority of nutrition societies internationally, as well as to academic institutions that teach nutrition. Such a manual could also be used for explaining the importance of harmonization, including justification for making resources available globally. The manual could contain such information as:
- A clear explanation of terminology;
- A description of available resources, such as existing systematic reviews and databases;
- Guidance on when to include or exclude data from systematic reviews, and how to establish endpoints;
- Methods used to assess status and requirements for each nutrient;
- Information on bioavailability adjustments, with case studies to explain the process for some specific nutrients;
- Guidance on how to manage factors such as dietary patterns, life stage concerns, genetic variability, morbidity and infections, and physiological requirements;
- How to use the AR and UL to estimate the prevalence of inadequate and excessive intakes, respectively, in population subgroups; and
- For each nutrient, a description of symptoms and problems caused by exceeding the UL of intake.
Global consensus on gaps in scientific information could help to drive a new agenda for obtaining this information and funding the necessary research.
Recommendation 6. Researchers and funding organizations should advance the knowledge of nutrient requirement research by supporting research that uses modern technology, techniques, or methods for assessing requirements.
To facilitate local and regional implementation of a harmonized process to derive NRVs, there is a need for additional guidance (i.e., beyond what is here) on how to use the tools and apply the steps identified in the proposed framework in this report (see Chapter 3, Figure 3-4). Such guidance could include information on:
- Managing missing ARs;
- Increasing the availability of local and regional data;
- Encouraging regional working groups and partnerships;
- Clarifying data uncertainties, such as food intake and composition data limitations; and
- Facilitating access to harmonization tools, for example, through a “Secretariat” or other international organization.
While this report describes the data gaps and offers a model for harmonizing the approach to deriving NRVs globally, future dialogue will be needed across countries to garner support for a harmonization effort and to identify a pathway for implementing the recommendations of this report. It is the committee’s view that achieving global harmonization of the
methodological approaches to deriving NRVs requires that the following overlapping steps be taken:
- Design a process by which harmonization can be achieved.
- Test the proposed process.
- Implement the process.
- Communicate and support the incorporation of the results of harmonization at all levels (i.e., country, regional, global).
- Perform process and outcome evaluations throughout.
Each of these steps entails specific activities that are key to the harmonization of methodologies to derive NRVs. The first two steps are encompassed in the activities that resulted in the convening of the Global Harmonization workshop and the subsequent work of this consensus committee and its report. This report’s intent is to provide the guidance needed as global stakeholders consider moving toward the subsequent steps of implementation, communication, and evaluation.
An important next step (as part of implementation and communication) is for the key enablers of harmonizing NRVs to develop a tool kit that participants from low- and middle-income countries can use to guide the development of harmonized approaches to deriving NRVs for their populations. To be effective and useful, the NRVs for a specific country or region need to address specific economic, social, and cultural influences on the food supply and the population’s nutritional status. Systematic reviews of NRVs from other countries will identify the key factors that need to address specific economic, social, and cultural influences on the food supply and the population’s nutritional status. Systematic reviews from other countries can be used to identify the key factors that need to be addressed when deriving NRVs, and possibly, to adjust estimated NRVs based on variations in the food supply, physical activity, and usual body size.
The path forward requires active participation and investment from groups and organizations to whom global harmonization will be entrusted. This may include WHO and FAO at the global level; nongovernmental stakeholder organizations and foundations at the regional level; and the joint U.S. and Canadian Dietary Reference Intake steering committee, the European Food Safety Authority, and other federal-level agencies at the national level. The collective effort of these groups is needed to launch an initiative that will explain the proposed harmonization approach and advocate for its implementation, including its advantages and the reasons for using a shared paradigm.
King, J. C., and C. Garza. 2007. Harmonization of nutrient intake values. Food and Nutrition Bulletin 28(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.