Harmonizing the Process for Establishing Nutrient Reference Values A Tool Kit (2020) / Chapter Skim
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Part 3: Developing a Harmonized Process for Deriving Nutrient Reference Values
Part 3: Developing a Harmonized Process for Deriving Nutrient Reference Values
Pages 13-27
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From page 13... ...
Currently in Use Around because they are critical for evaluating and planning the World, in Harmonization of population-level nutrient intakes. Estimates of the Approaches to Nutrient Reference Values (NASEM, prevalence of inadequate intakes in a population 2018b)
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Body size Dietary patterns Risk assessment* Upper limit Nutrient intakes Local and regional factors Biomarkers Risk of chronic disease FIGURE 2 Framework for deriving key nutrient reference values.
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assessment of the prevalence of intakes outside the reference values, and (4) characterization of risks associated with excess intake.
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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. Three main tools and resources are needed: systematic reviews, comprehensive databases, and information about relevant local and regional factors.
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o Population(s) of interest – consider demographic factors, including age, sex, ethnicity, and their public health significance o Intervention/exposure to the nutrient of interest – exclude research when the exposure dose is outside the biologically significant range o Comparator – for randomized controlled trials (RCTs)
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Databases Food intake and composition data are needed to estimate the appropriate bioavailability factors to apply to local diets. However, once the AR and the UL for nutrients have been determined, having nutrient intake data that is compared to the AR and UL is key to estimating the prevalence of inadequate and excessive intakes, respectively, of specific nutrients among population groups.
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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.
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Gather and Review Data The second major step in setting key NRVs involves collecting the relevant data from the tools and other resources.
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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)
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* Recommended nutrient intake based on the bioavailability of the diet as recommended by the 2008 FAO/WHO Human Vitamin and Mineral Requirements.
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. Examples of approaches for determining key reference values include: • Currently, the derivation of recommended intakes for For more information iron and zinc are based on the factorial approach.
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Typically, 15-35 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.
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The first step in deriving NRVs is to define the AR. Nutrient requirements, defined as the lowest continuing intake level of a nutrient that maintains a defined level of nutrition for a given criterion of nutritional adequacy in an individual, form the basis for the AR (IOM, 2000; Yates, 1998)
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Both dietary phytate and non-heme iron are more prevalent in the food supplies among low- and middle-income countries, thus contributing to a higher prevalence of deficiency and increased physiologic requirement in those populations. Additionally, iron stores, a biomarker of iron status, can be modified by chronic disease, infection, or other nutrient deficiencies, further contributing to increased physiologic requirements for this nutrient (NASEM, 2018b)
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Proposed Harmonized Nutrient Reference Values for Populations have been published; ideally these would continue to be revised and be supported by an authoritative international body for global application (Allen et al., 2020)
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