By Harold McGee
The most common ingredients that provide sugar-like bulk are the sugar alcohols, or polyols—chemicals whose names end in -itol—which are essentially sugars with one corner of their molecule modified (for example, sorbitol is derived in this way from glucose). Small amounts of some sugar alcohols—sorbitol, mannitol—are found in many fruits and plant parts. Because the human body is designed to make use of sugars, not sugar alcohols, we absorb only a fraction of these molecules from food, and use that fraction inefficiently: so they cause only a slow rise in blood insulin levels. The rest are metabolized by the microbes in our intestines, and we obtain their energy indirectly. All told, sugar alcohols provide 50–75% of the caloric value of sugar.