Category: sweetener
Aliases: E967, Birch sugar, Xylit, Sugar alcohol, Polyol, Pentitol, meso-Xylitol, Xylo-pentane-1,2,3,4,5-pentol
A five-carbon sugar alcohol (pentitol, C5H12O5) used as a bulk sweetener at roughly the sweetness of sucrose but with about 40% fewer calories. It is absorbed slowly and incompletely from the small intestine by passive diffusion (no active transporter), so a large fraction reaches the colon, where bacterial fermentation produces short-chain fatty acids and gas and exerts an osmotic, laxative effect at high intake. The absorbed portion is metabolised mainly in the liver via the glucuronate–xylulose (uronic-acid) pathway: NAD-linked xylitol dehydrogenase oxidises it to D-xylulose, which is phosphorylated by xylulokinase to xylulose-5-phosphate and enters the pentose-phosphate pathway. Because hepatic uptake and metabolism are largely insulin-independent, the glycaemic and insulin response is minimal. It is also non-fermentable by oral Streptococcus mutans, underpinning its anti-cariogenic use.
E967; about as sweet as sucrose (~1.0×) with ~2.4 kcal/g; EFSA/JECFA assign no numerical ADI ("not specified"), and it is GRAS/permitted in the EU and US. Key flags: osmotic diarrhoea above roughly 30–50 g/day (GI tolerance threshold), and it is acutely toxic to dogs (hypoglycaemia and hepatic failure), so xylitol-containing products must be kept away from pets.