The rationales for the AIs vary by nutrient and are summarized in Box 8-1.
Water For water, the focus primarily was on dehydration as an end point, and serum or plasma osmolality was the indicator used. Examining data on water intake and osmolality from the Third National Health and Nutrition Examination Survey, no evidence of dehydration was found in the general population, even at the first decile of water intake. Serum osmolality basically was identical across the reported intakes. Thus the median water intake was used to set the AI, which is consistent with the definition of AI.
Sodium For sodium, “nutrient adequacy” refers to the sodium intake level at which one could consume a diet that basically meets all the recommended dietary intakes for other nutrients. Of several hypothesized adverse effects of inadequate sodium intake, only nutrient inadequacy and volume depletion in the setting of acute thermal stress were considered to be sufficiently well documented to use in setting the AI.
Potassium A controlled feeding study (Morris et al., 1999) was one of several pieces of data that contributed to the basis for the AI of 1,500 mg (120 millimoles) of potassium per day. The investigators fed different
Rationale for Adequate Intake, by Nutrient
NHANES III = Third National Health and Nutrition Examination Survey