(A normal or symmetrical distribution [median and mean are similar] is usually assumed for nutrient requirements.) This use follows the precedent set by others that have used the term “Estimated Average Requirement” for reference values similarly derived, but meant to be applied to population intakes (COMA, 1991).

The EAR’s usefulness as a predictor of an individual’s requirement depends on the appropriateness of the choice of the nutritional status indicator or criterion and the type and amount of data available. The general method used to set the EAR is the same for all nutrients. The specific approaches differ since each nutrient has its own indicator(s) of adequacy, and different amounts and types of data are available for each. Thus, coupled with an estimate of the variance in requirements, the EAR has served three major functions: as the basis for the RDA, as the primary reference point for assessing the adequacy of estimated nutrient intakes of groups (IOM, 2000a), and, together with estimates of the variance of intake, in planning for the intake of groups (IOM, 2003).

Recommended Dietary Allowance

The Recommended Dietary Allowance (RDA) is an estimate of the minimum daily average dietary intake level that meets the nutrient requirements of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group (see Figure 4-2). The RDA is intended to be used as a goal for daily intake by individuals as this value estimates an intake level that has a high probability of meeting the requirement of a randomly chosen individual (about 97.5 percent). However the RDA is not an appropriate value to use to assess the adequacy of intakes. The process for setting the RDA is described below; it depends on being able to set an EAR and estimating the variance of the requirement itself. Note that if an EAR cannot be set due to limitations of the data available, no RDA will be set.

This approach differs somewhat from that used by the World Health Organization, Food and Agriculture Organization of the United Nations, and International Atomic Energy Agency (WHO/ FAO/IAEA) Expert Consultation on Trace Elements in Human Nutrition and Health (WHO, 1996). That publication uses the term basal requirement to indicate the level of intake needed to prevent pathologically relevant and clinically detectable signs of dietary inadequacy. The term normative requirement indicates the level of intake suffi-

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