Sodium
The value of salt has been recognized for centuries. The common expressions of “salt of the earth” and even the word “salary” all derive from high value placed upon salt throughout history.
The requirement for sodium is not well defined, but human dietaries generally contain more sodium than necessary.
Tissue formation, as in growth, requires about 1.1 -1.2 mg/kg of tissue gained; the requirement for maintenance should be considerably less.
Intakes vary widely; about 10 gm NaCl/day appears to be usual for most Americans, whereas intakes of 30 – 40 gm/day are not uncommon in Oriental countries where soy sauces and sodium glutamate are flavored as flavoring agents.
The human body contains about 1.8 gm Na/kg at free bodyweight, most of which is present in extracellular fluids.
The content of serum normally is about 140 mEg/liter .
Since sodium is the chief cation of the extracellular fluid, the control of the body fluid osmolarity and therefore body fluid volume is largely dependent on sodium ions and the ratio of sodium to other ions.
Sodium
