Conversion of sorbitol to mannitol when used parenterally.

Conversion of sorbitol to mannitol was shown by the unexpected discovery of the urinary excretion of mannitol when urinary levels were being measured in connection with the surveillance of patients suffering from malnutrition or head injury and receiving total parenteral nutrition: glucose, sorbitol, amino acids and soya oil. The presence of mannitol in thr urine would appear to result from a secondary catabolism through a physiological pathway for the fructose produced by the metabolism of sorbitol not broken down during glycolysis.