A small change in the structure of a chemical may make a major difference in its physical, nutritional and biological properties. A simple alteration of the sugar glucose converts it into the alcohol sorbitol. Despite their chemical differences, these compounds share many attributes. Together, sorbitol and glucose play an important role in your health.
Chemical Structure
Sorbitol and glucose differ by just two hydrogen atoms. The chemical formula for glucose is C6H12O6 and its molecular weight is 180.16. The molecular formula for sorbitol is C6H14O6 and its weight 182.17. Both are white, odorless powders. Both readily dissolve in water, and both are "D" or right-handed molecules. D-glucose and D-sorbitol rotate polarized light to the right.
Occurrence in Nature
Sorbitol and glucose are naturally occurring and interdependent chemicals common in plants and animal. Sorbitol is produced naturally by reducing or adding two electrons and two hydrogen atoms to the glucose molecule. This is an intentional chemical reaction facilitated by a specific enzyme. Sorbitol is then converted to the sugar fructose by another enzyme. Beet and cane plants combine glucose and fructose to produce sucrose or table sugar. Sorbitol and glucose used commercially are both derived from plant sources or created synthetically.
Use as Sweeteners
Sorbitol and glucose are both sweet tasting, but neither is as sweet as sugar. Glucose has a slight sweetness advantage over sorbitol. Glucose is 74 percent as sweet as sugar, while sorbitol is about 60 percent as sweet. Sorbitol has about one-third fewer calories than table sugar. Glucose has about 20 percent fewer calories than table sugar. You can use both to sweeten food, though glucose is often added to increase rather than reduce calories.
Role in Diabetes
Diabetics should be cautious when eating foods with added glucose or sorbitol. Diabetics often experience damage to their nerves and eyes. This damage may not be entirely due to hyperglycemia, but rather the glucose metabolite sorbitol. Both glucose and sorbitol are present within cell tissue, but sorbitol does not freely cross cell membrane walls. As sorbitol accumulates inside the cell, pressure increases and nerve cell damage or neuropathy can result.
The researchers of a study published in the "Journal of Neurology, Neurosurgery, and Psychiatry" in June 1981 demonstrated the relationship of sorbitol to neuropathology indirectly by treating hyperglycemic human subjects with a drug that inhibits the conversion of glucose to sorbitol. While there were no improvements to the health of the eye in these subjects, there were improvements in other forms of neuropathology -- even though blood glucose levels remained high.
References
- Chemistry Daily: Glucose
- ChemicalBook: D-Sorbitol
- "Journal of Neurology, Neurosurgery, and Psychiatry"; Effects of Aldose Reductase Inhibitor Treatment in Diabetic Polyneuropathy: a Clinical and Neurophysiological Study; Jan Fagius, et al.; June 1981
- Calorie Control Council: Sorbitol
- Nordic Sugar: Sweetness
- UC Clermont College Biology; Biology 104: Carbohydrates; J. Stein Carter
