Sodium Chloride, Potassium Chloride, Vitamin B12
Our bodies lose approximately 2-3 liters a day of fluid when sedentary and this can increase to 10-15 liters in intensively training athletes, especially in warmer climates.
With increasing fluid loss comes increasing electrolyte loss, and these too need to be replenished. In addition to water, the primary components of sweat are sodium, potassium and chloride, with smaller concentrations of magnesium and calcium. A major limitation associated with re-hydration and electrolyte repletion is absorption. Replenishing lost electrolytes is typically accomplished by consuming drinks which cause over-hydration.
† These statements have not been evaluated by the Food and Drug Administration.