The term macrominerals refers to those elements needed by the body in milligram quantities on a daily basis. The category includes sodium, potassium, chloride, calcium, phosphorus, and magnesium. While the body content of the first three is relatively small because of high turnover, the body content of calcium and phosphorus, by comparison, is relatively large. All of these serve as electrolytes and their critical use relates to this function. Sodium is the major extracellular electrolyte. It has an atomic number of 23 and circulates as a fully dissociated ion due to its 1+ charge. It is thus fully water soluble. It has been estimated that the adult body contains 52 to 60 meq/kg (male) and 48 to 55 meq/kg (female). The system which regulates sodium levels in the blood also is involved in the regulation of water balance, pH, and osmotic pressure. Both hormones and physical/chemical factors are involved.