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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
tential role of the nutrient in the reduction of disease risk was considered in developing the EARs and AIs. With the acquisition of additional data relating intake to chronic disease or disability, the choice of the criteria used for setting these DRIs may change.
PARAMETERS FOR DIETARY REFERENCE INTAKES
Life Stage Groups
The life stage groups described below were chosen by keeping in mind all of the nutrients to be reviewed, not only those included in this report (see IOM, 1997). Additional subdivisions within these groups may be added in later reports. If data are too sparse to distinguish differences in requirements by life stage or gender group, the analysis may be presented for a larger grouping.
Infancy covers the period from birth through 12 months of age and is divided into two 6-month intervals. The first 6-month interval was not subdivided further because intake is relatively constant during this time. That is, as infants grow, they ingest more food; however, on a body weight basis their intake remains the same. During the second 6 months of life, growth velocity slows, and thus total daily nutrient needs on a body weight basis may be less than those during the first 6 months of life.
For a particular nutrient, the average intake by full-term infants who are born to healthy, well-nourished mothers and exclusively fed human milk has been adopted as the primary basis for deriving the AI for nutrients during the first 6 months of life. The value used is thus not an EAR, and it is not assumed that such data will become available. The extent to which intake of human milk in the amounts recommended may result in exceeding the actual requirements of the infant is not known, and ethics of experimentation preclude testing levels known to be potentially inadequate.
Using the infant that is fed human milk as a model is in keeping with the basis for estimating nutrient allowances of infants as was developed in the last Recommended Dietary Allowances (RDA) (NRC, 1989) and Recommended Nutrient Intakes (RNI) (Health Canada, 1990) reports. It also supports the recommendation that exclusive human milk feeding is the preferred method of feeding for normal full-term infants for the first 4 to 6 months of life. This recommendation has also been made by the Canadian Paediatric