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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
and the recommended intakes and consider possible reasons for such discrepancies.
Considered the need to protect individuals with extreme or distinct vulnerabilities due to disease conditions or genetic predisposition.
Weighed the alternatives and set priorities based on expert judgment.
MAJOR KNOWLEDGE GAPS
To derive an Estimated Average Requirement (EAR), a criterion must be selected for a particular status indicator or combination of indicators that is consistent with impaired status as defined by some clinical consequence or accepted biomarker for that consequence.
For sodium, potential biochemical indicators of adequate intake included increased plasma renin activity, adverse changes in lipid concentrations, and increased insulin resistance. Nonbiochemical indicators were nutrient inadequacy and sodium imbalance. In predominantly short-term studies, a reduced sodium intake increased plasma renin activity, but the clinical relevance of increased plasma renin activity is uncertain. The best available evidence did not support adverse changes to lipid concentrations. Data were insufficient to determine whether chronic ingestion of sodium in clinically relevant ranges led to deterioration in insulin resistance. Achieving an adequate intake of other nutrients is a potential concern at extremely low levels of intake. Sodium imbalance, that is, sodium losses that exceed intake, might occur when sweat sodium losses are high, as in the setting of extreme heat or extreme physical activity, particularly in persons who are unacclimatized to these environmental conditions. Overall, there was no single indicator that could be used to assess adequacy of intake, and thus a combination of indicators was used.
For potassium, serum potassium concentration and hypokalemia are insensitive markers of inadequate intake. Biochemical markers of inadequate potassium intake are needed.
For water, plasma or serum osmolality is an acceptable indicator of hydration status; however, trials that rigorously control and test different levels of total water intake, rather than allowing ad libitum intakes, have not been performed.