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Major findings in this report include the following:

  • The establishment of Adequate Intakes (AIs) for total water (which includes drinking water and the water content of beverages and food), potassium, sodium, and chloride.

  • The establishment of a Tolerable Upper Intake Level (UL) for sodium and chloride.

  • Research recommendations for information needed to advance the understanding of human requirements for water and electrolytes as well as adverse effects associated with intakes of excessive amounts of water, sodium, chloride, potassium, and sulfate.

APPROACH FOR SETTING DIETARY REFERENCE INTAKES

The scientific data used to develop Dietary Reference Intakes (DRIs) have come primarily from observational and experimental studies conducted in humans. Studies published in peer-reviewed journals were the principal source of data. Life stage and gender were considered to the extent possible. Three of the categories of reference values—the Estimated Average Requirement (EAR), the Recommended Dietary Allowance (RDA), and the Adequate Intake (AI)—are defined by specific criteria of nutrient adequacy; the fourth, the Tolerable Upper Intake Level (UL), is defined by a specific endpoint of adverse effect, when one is available (see Chapter 1 for an overview of the approach).

In all cases, data were examined closely to determine whether a functional endpoint could be used as a criterion of adequacy. The quality of studies was examined by considering study design; methods used for measuring intake and indicators of adequacy; and biases, interactions, and confounding factors.

Although the reference values are based on data, the data were often scanty or drawn from studies that had limitations in addressing the various questions that confronted the panel. Therefore, many of the questions identified regarding the requirements for and recommended intakes of these electrolytes and of water cannot be answered fully because of inadequacies in the present database. Accordingly, a research agenda is proposed (see Chapter 9). In particular, there was a dearth of large, dose-response trials with clinically relevant biological outcomes (considered indicators of adequacy or excess). The absence of such studies is not unique to water and electrolytes. Rather, there are substantial feasibility considerations that preclude the conduct of such trials, especially when the



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