The Science Behind Oral Rehydration Therapy

The Sodium Glucose Pump

The most rapid and effective way to manage mild to moderate dehydration is to activate the Sodium-Glucose Co-Transporter (or pump) located in the intestinal mucosa (enterocytes) of the small intestine. These special cells activate when they encounter the correct ratio of sodium and glucose in water. This causes the body to absorb these molecules and rapidly absorb water in the process.


In addition to the having the correct formula to activate the sodium-glucose pump, an oral rehydration solution must also have the correct tonicity to be effective.
Tonicity is the relative concentration of solutes dissolved in solution, determining both the direction and extent of water movement across a semi-permeable membrane.

  • A hypotonic solution has a lower concentration of solutes compared to another solution
  • A hypertonic solution has a higher concentration of solutes compared to another solution
  • An isotonic solution has the same concentration of solutes compared to another solution

Water molecules move from an area of high concentration to an area of low concentration.
Hydralyte is hypotonic vs. your body’s cells – it has a higher concentration of water molecules. Therefore, when the sodium-glucose pump is activated, water will flow through.
The diagram helps to illustrate the effects of solutions of differing tonicity levels on red blood cells.


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