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Harmonizing the Process for Establishing Nutrient Reference Values: A Tool Kit Chapter: Part 3: Developing a Harmonized Process for Deriving Nutrient Reference Values. Get This Book.
Visit NAP. Looking for other ways to read this? No thanks. Suggested Citation: "Part 3: Developing a Harmonized Process for Deriving Nutrient Reference Values. Harmonizing the Process for Establishing Nutrient Reference Values: A Tool Kit.
Washington, DC: The National Academies Press. doi: Part 3: Developing a Harmonized Process for Deriving Nutrient Reference Values Currently, countries and organizations use varying terminology to express nutrient reference values NRVs.
Four of these NRVs are considered to be the core reference values—the average requirement AR , the recommended nutrient intake RNI , the adequate intake AI , and the upper level of intake UL : AR.
The amount of a nutrient estimated to meet the nutrient requirement of 50 percent of the healthy individuals in a population. RNI derived from the AR. The average daily intake for a nutrient that is sufficient to meet the requirements of percent of the population.
The recommended average intake of a nutrient based on observed or experimentally determined estimates for an apparently healthy population. This value is derived when evidence for an AR is insufficient.
The highest average daily nutrient intake that is likely to pose no risk of adverse effects to most individuals in a population. It does not include acute or episodic high intakes that might be consumed in a supplement, for example.
Page 14 Share Cite. The framework, shown in Figure 2 , has four core elements: Choose the appropriate tools and data resources. Collect data from the tools and resources. Identify the best approach for the nutrient under consideration.
Derive the two key reference values—AR and UL. FIGURE 2 Framework for deriving key nutrient reference values. Systematic reviews and databases inform how local and regional factors are considered.
Page 15 Share Cite. Critical Characteristics In addition, the following characteristics are critical to the NRV review process and help to support harmonization of the approaches to setting NRVs across multiple countries.
NRVs must be: Regularly updated. Given the rapid pace of the generation of knowledge and data on which NRVs are based, it is important to maintain the currency of information on nutrient outcomes as well as the nutritional profile of populations, particularly as supplement use increases and fortification programs are established.
Confidence in the systematic reviews that lead to updated or new NRVs is necessary to ensure their use by policy makers as well as researchers. Such credibility requires the establishment of a transparent process that covers how members of the review panels are selected and the training and expertise of each; public availability of all material reviewed by the committee during its deliberations; and written protocols for systematic reviews, quality assessment of each study, assumptions made, and evidence synthesis leading up to setting the NRVs.
Consistent methods need to be established and applied across nutrients, for various values e. A uniform approach for conducting systematic reviews and establishing values for nutrients in cases where evidence is limited also is needed. Given the changing epidemiologic and nutritional status across populations, values need to be relevant to contexts where chronic disease is rising, in addition to being relevant to the prevention of deficiency.
At each stage in the process, all considerations or adjustments that influence the potential NRV must be documented, as must the methodologies used and the assumptions behind them. Based on a determination of the strength of the evidence.
Limitations in the data and methods must be assessed and documented and uncertainties taken into account. Page 16 Share Cite. Complete and efficient. Given the cost, time, and expertise required to undertake the development or revision of existing reference values, even in high-income countries, low- and middle-income countries could consider using existing NRVs developed by another international partner if they are deemed adequate.
Using the Framework to Derive Nutrient Reference Values The first major step in the framework is choosing the appropriate tools and resources for reviewing and assessing the evidence. Collect Tools and Resources Systematic Reviews Systematic reviews are a rigorous and transparent method of collecting and synthesizing relevant published literature.
Page 17 Share Cite. Assessing uncertainty in the evidence. Evaluating the risk of bias is an essential step in systematic reviews and requires an assessment of the internal and external validity of each study included in the review. Bias occurs when the results of the review are distorted by systematic flaws or limitations in the design or conduct of a study.
They can be introduced at various points in a study and are important to identify because they can affect the conclusions and the interpretation of results. A number of tools have been developed in recent years to evaluate different types of risk of bias.
Page 18 Share Cite. Assessing uncertainty in the review process. A shortcoming common to many systematic reviews is that they pool studies that use different types of evidence, such as various study designs, different populations, or the use of animal and human data.
Because this heterogeneity leads to uncertainty, pooling studies should be conducted only when they meet meta-analysis criteria. Evidence mapping—a way to systematically identify, organize, and summarize available studies and identify gaps and research needs—can help to reduce this bias. Databases Food intake and composition data are needed to estimate the appropriate bioavailability factors to apply to local diets.
Page 19 Share Cite. Physiologic changes that accompany aging e. muscle strength and bone mass can affect physiological and metabolic responses to nutrient intake Host condition, dietary, and environmental factors can affect nutrient bioavailability, thereby altering physiological and dietary requirements Food Consumption and Food Composition Databases Many countries have their own food intake databases, but regional and global databases are also available and may be useful.
Databases of Relevant Recent Extant Systematic Reviews The cost of doing new systematic reviews can be very high. Key References from Nutrient Expert Groups A list of these key references can be found in Appendix 3: Websites for Tools and Resources.
Other Tools A panel convened to decide whether to update or adapt existing NRVs might appraise existing NRVs using an adaptation of the Appraisal of Guidelines for Research and Evaluation II AGREE II tool.
Page 20 Share Cite. Gather and Review Data The second major step in setting key NRVs involves collecting the relevant data from the tools and other resources. Page 21 Share Cite. Examples of data include: Biomarkers of nutrient status. Biomarkers are presently only available to assess various stages of depletion for some nutrients.
Biochemical analyses include both static and functional tests. Static tests measure either a nutrient or its metabolite in biological fluids or tissues, including urinary levels. Functional tests may reflect later stages in the development of nutrient deficiencies or shifts in nutritional status associated with reductions in chronic disease.
Anthropometric measurements of physical dimensions or body composition, including bone, while not specific, are useful if there are imbalances of protein and energy intakes, but they do not reflect specific nutrient deficiencies.
A medical history and physical examination are nonspecific and only develop in the advanced stages of nutritional deficiencies Combs et al. Bioavailability algorithms. The bioavailability of a nutrient in any food refers to the degree it is absorbed, transported, and used physiologically.
Because the dietary factors influencing nutrient absorption or utilization are not well established for many nutrients, algorithms to predict bioavailability are unavailable for most nutrients. The exceptions are iron and zinc. These mathematical models predict bioavailability by determining the amount and form of iron or zinc, the presence of dietary enhancers and inhibitors, and the iron and zinc status of the individual.
The accuracy of bioavailability algorithms is limited by the interactions occurring between the enhancing and inhibiting factors in the whole diet.
For example, the effect of enhancers e. Bioavailability algorithms need to be revised regularly as quantitative information on the effect of dietary components on nutrient absorption and utilization becomes available.
Nutrient bioavailability software. The increased availability of electronic nutrient composition databases provides an opportunity to consider the bioavailability of nutrients when micronutrient intakes are estimated for various population groups.
An example is the development of software called the Calculator of Inadequate Micronutrient Intake CIMI to assess nutrient intake as well as the bioavailability of iron and zinc Radix et al. This program calculates the bioavailability of iron and zinc in the individual diet.
The bioavailability factor was determined using several scenarios of the percentage of bioavailability. For example, if more than 5 percent of total energy intake is accounted for protein from fish and meat, the iron bioavailability is 15 percent.
The classification of iron and zinc bioavailability is. Page 22 Share Cite. shown in Table 1 below. Nutrient availability modeling software.
Software for converting nutrient intake data to prevalence of inadequate intakes is now available. One example is Intake Monitoring, Assessment and Planning Program IMAPP at Iowa State University. Moderate If none of the described conditions is met.
SOURCE: Radix et al. Usual activity levels. Questions regarding the type and level of habitual physical activity or exercise should be included when energy intakes are evaluated. A number of physical activity questionnaires are available Sylvia et al.
The correlation between the available questionnaires and an objective measure of activity or fitness such as accelerometers tends to be low. Also, the questionnaires tend to overestimate physical activity by nearly 85 percent Lee and Carlisle, Page 23 Share Cite. Identify the Best Approach The third major step is identifying the best approach for determining key reference values.
Examples of approaches for determining key reference values include: Currently, the derivation of recommended intakes for iron and zinc are based on the factorial approach. For example, dietary zinc recommendations are based on the amount of absorbed zinc needed to replace endogenous zinc losses including fecal and non-intestinal losses i.
The endogenous fecal zinc losses vary with the amount of zinc absorbed that increases with increased zinc intakes. A number of zinc biomarkers have been measured i. Page 24 Share Cite. Like zinc, the physiological iron requirements are based on the amount needed to replace total losses from the intestine, urinary tract, skin, and menstrual losses in women or semen in men.
Total losses average 0. Major determinants of dietary iron requirements are the proportion of iron from heme in the diet and the sources of non-heme iron. Typically, percent of the heme iron is absorbed while non-heme iron absorption can range from 2 to 20 percent, depending on the type of grain or legume and the amount of phytate in the diet that limits iron absorption.
As is true for zinc, there are a number of problems in establishing recommended iron intakes using the dose—response method. For example, the bioavailability of dietary iron has a poor correlation with iron status. Sensitive, specific biomarkers of iron status are limited and many are affected by other factors i.
Page 25 Share Cite. Derive Key Reference Values The final step in the process is to derive the two key NRVs—AR and UL. Page 26 Share Cite. FIGURE 3 Relationship between nutrient reference values. Page 27 Share Cite. FRAMEWORK SUMMARY Developing the key nutrient reference values i.
The process for deriving harmonized standards is based on six core principles: The NRVs are regularly updated. The process is clear and transparent. The methods are rigorous and relevant. Factors influencing the NRV are documented.
The strength of the evidence is determined. The review is complete and efficient. Recommended Dietary Allowances RDAs for protein, energy, and eight vitamins and minerals.
This was followed by periodic revisions of the U. FAO Food and Nutrition Series No. FAO, Rome. By , the U. S RDAs included 25 vitamins and minerals in addition to protein and energy. Gibson RS 1 , Principles of Nutritional Assessment: Development of Nutrient Reference Values 3rd Edition March, Abstract This chapter describes the evolving process of setting nutrient reference values NRVs from a single value to a multi-level approach designed to address multiple users and needs.
This multi-level approach with some modifications has been adopted by several authoritative groups. However, discrepancies in the terminology and methodologies has led to an initiative to develop a four-step framework for harmonizing the process for deriving two core NRVs.
The feasibility of the proposed framework has been tested with three exemplar micronutrients zinc, iron, folate on two high-risk population subgroups — young children and women of reproductive age.
The framework can be applied across countries and a variety of population subgroups, while taking into account culturally and context-specific food choices and dietary patterns. Derivation of the two core NRVs depicted in the framework — the Average Requirement AR and Safe Upper Level of Intake UL — is presented here.
Details of additional NRVs used are also described. Details of the different methods used to establish recommendations for energy and macronutrients are also described.
Box 8a. What are the most important characteristics of the population? Modified from NASEM b.
Not a MyNAP member yet? Register Harmonized nutrient variety a free account to start nuttient and receiving special varietj only perks. Harmonized nutrient variety, countries and nuttient use Hxrmonized terminology to express Harmonized nutrient variety reference values NRVs. Caffeine and power output of these Haemonized Harmonized nutrient variety Harmonuzed to Harmnized the core reference values—the average requirement ARthe recommended nutrient intake RNIthe adequate intake AIand the upper level of intake UL :. Of these four values, RNIs and AIs are considered to be of lesser priority. RNIs are the basis for individual dietary planning and AIs are used because they serve as an indicator of possibly low intakes and are used when it is not possible to derive an AR. ARs and ULs are the priority NRVs because they are critical for evaluating and planning population-level nutrient intakes. The varidty of laws and regulations for food products Harmonized nutrient variety considered Muscle recovery supplements be highly desirable, Harmmonized the vaeiety has been recognized nutrieny the early Harmonjzed. The main milestones in global standardization Harmonized nutrient variety harmonization of food legislation are shown in Table 1. Table 1: Milestones in Global Standardization and Harmonization of Food Legistation 1,2,4,5. Policy Differences and Degree of Harmonization. In Southeast Asia, significant differences are found in nutrition labeling and food claims among the countries, and harmonization does not seem to be important at this time. Revisions were adopted in AprilOctoberand January
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