Re: what is an electrolyte?

Electrolytes are single, electrically charged particles that are dissolved 
in blood and body fluids.  When we think of electrolytes, we usually think 
of sodium, potassium and chloride.  These electrolytes help the body to 
regulate the amounts of water inside and outside the cells so that the 
cells do not collapse from too much water leaving them or swell from having 
too much water inside them.  Sodium is the major positively charged ion 
outside the cells; potassium is the major positively charged ion inside the 
cells.  Chloride is the major negatively charged ion outside the cells.  
These ions need to be balanced inside and outside the cell.  For example, 
if you take in a lot of sodium and no water (which is not a good idea, by 
the way), water will leave the inside of the cells to maintain the balance 
between the concentration of sodium outside the cells with the 
concentration of potassium inside the cells.  As another example, when you 
lose water such as through sweating, you lose electrolytes as well.  If you 
lose enough water and electrolytes, your body is unable to function as well 
.  In extreme cases, a person may have a heat stroke where the body is 
unable to maintain its temperature anymore and many body systems shut down. 
  
Reference:  Marie Boyle.  Personal Nutrition, Fourth Edition. 2001