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clinical outcome is a chronic disease. The reasoning used to establish the values is described for each nutrient reviewed in Chapters 4 through 7.

While the various recommendations are provided as single rounded numbers for practical considerations, it is acknowledged that these values imply a precision not fully justified by the underlying data from currently available human studies.

Box S-1 provides definitions of each of the categories of Dietary Reference Intakes applicable to electrolytes and water. To establish a Recommended Dietary Allowance (RDA), by definition it is necessary to be able to estimate an intake level that would meet the requirement of half of the individuals in the subgroup of the population for whom the recommendation is made; estimating this average requirement (EAR) requires that there be sufficient dose-response data relating intake to one or more criteria or functional endpoints that are reasonably sensitive to the presence or absence of the nutrient.

None of the nutrients reviewed in this report had sufficient dose-response data to be able to set an EAR, and from that derive an RDA. Thus, for each nutrient, with the exception of sulfate, an adequate intake (AI) is set. The indicators used to derive the AIs are

BOX S-1 Dietary Reference Intakes: Definitions

Recommended Dietary Allowance (RDA): the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.

Adequate Intake (AI): the recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate—used when an RDA cannot be determined.

Tolerable Upper Intake Level (UL): the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects may increase.

Estimated Average Requirement (EAR): the average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular life stage and gender group.

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