Xylitol has the chemical formula C5H12O5. It is a straight chain five carbon aliphatic compound with two -OH groups. Each -OH group is present on each terminal carbon. Because of this structure it falls under the category of poly-alcohols or "polyols."
Xylitol is produced mainly from birch trees, oat husks and mushrooms. The process of producing xylitol involves the conversion of naturally occurring xylan molecules into D-xylose. The D-xylose sugar molecules are then converted to xylitol by column chromatography. Another method to produce xylitol is by chemical synthesis procedures or by bacterial fermentation using genetically modified bacteria. However, these synthesis methods are not economically viable.
In humans, xylitol is produced as an intermediate step during the metabolism of carbohydrates. Xylitol is converted to p-xylulose. Xylulose is further converted to Xylulose-phosphate via phosphate transfer from ATP. Further, the xylulose phosphate is converted to ribulose by an epimerase. The ribulose phosphate now participates in the pentose phosphate pathway. In this pathway, a pentose (five carbon sugar) phosphate is converted to glucose-6 phosphate by the nonoxidative reversible phase of this pathway. Thus, the xylitol through a series of metabolic steps is converted to glucose-6-phosphate that can now participate in glycolysis.
Xylitol is favored by dentists as a sugar substitute because unlike sugar it does not cause tooth decay. According to Dr. Makinen, for this strategy to be effective, one needs to consume between six and 12 g of xylitol a day. There is an initial period of adaptation of xylitol when the dosage should be increased over time.
Excessive consumption of xylitol can lead to flatulence and diarrhea.