|Systematic IUPAC name
(2R,3R,4S)-Pentane-1,2,3,4,5-pentaol (not recommended)
3D model (JSmol)
|E number||E967 (glazing agents, ...)|
CompTox Dashboard (EPA)
|Molar mass||152.146 g·mol−1|
|Melting point||92 to 96 °C (198 to 205 °F; 365 to 369 K)|
|Boiling point||345.39 °C (653.70 °F; 618.54 K) Predicted value using Adapted Stein & Brown method|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Xylitol is a sugar alcohol used as a sugar substitute. The name derives from Ancient Greek: ξύλον, xyl[on], "wood" + suffix -itol, used to denote sugar alcohols. Xylitol is categorized as a polyalcohol or sugar alcohol (specifically an alditol). It has the formula CH2OH(CHOH)3CH2OH. It is a colorless or white solid that is soluble in water. Use of manufactured products containing xylitol may promote better dental health, but evidence is lacking on whether it prevents cavities.
Structure, production, occurrence
Xylitol is naturally occurring in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and animals make trace amounts during metabolism of carbohydrates. Unlike most sugar alcohols, xylitol is achiral. Most other isomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has a plane of symmetry.
Industrial production starts with lignocellulosic biomass from which xylan is extracted; raw biomass materials include hardwoods, softwoods, and agricultural waste from processing maize, wheat, or rice. The xylan polymers can be hydrolyzed into xylose, which is catalytically hydrogenated into xylitol. The conversion changes the sugar (xylose, an aldehyde) into the primary alcohol, xylitol. Impurities are then removed. The processing is often done using standard industrial methods; industrial fermentation involving bacteria, fungi, or yeast, especially Candida tropicalis, are common, but are not as efficient.
Xylitol is used as a sugar substitute in manufactured products, such as drugs or dietary supplements, confections, toothpaste, and chewing gum, but is not a common household sweetener. Xylitol has negligible effects on blood sugar because it is metabolized independently of insulin. Absorbed more slowly than sugar, xylitol supplies 40% fewer calories than table sugar. It is approved as a food additive in the United States.
Xylitol has about the same sweetness as sucrose, but more sweetness than similar compounds like sorbitol and mannitol. It has a glycemic index of 7 (100 for glucose). Because xylitol and other polyols are heat stable, they do not caramelise as sugars do, and they also lower the freezing point of mixtures in which they are used.
No health risk exists for normal levels of consumption, and the European Food Safety Authority has not set a limit on daily intake of xylitol. Due to the adverse laxative effect that all polyols have on the digestive system in high doses, xylitol is banned from soft drinks in the EU. Similarly due to a 1985 report, by the EU Scientific Committee on Food, stating that "ingesting 50 g a day of xylitol can cause diarrhea", tabletop sweeteners containing xylitol are required to display the warning: "excessive consumption may induce laxative effects". Chewing gum containing xylitol is permitted.
As of 2015, clinical trials examining whether xylitol alone or with other agents can prevent cavities found the evidence was too poor to allow generalizations, although when children with permanent teeth use fluoride toothpaste with xylitol, they may get fewer cavities than when using fluoride toothpaste without it. People apparently get fewer cavities when they chew gum sweetened with xylitol (or similar polyols such as sorbitol) than when they chew gum sweetened with sucrose.
In 2008, the European Food Safety Authority (EFSA) evaluated the literature on xylitol, concluding, "xylitol chewing gum reduces the risk of cavities in children". The claim required rewording because xylitol chewing gum is not a medicine, thus can "not be claimed to reduce the risk of a disease". In 2011, EFSA approved a claim that replacing sugar with xylitol and similar sweeteners "may maintain tooth mineralisation compared with sugar-containing foods."
Preventing ear aches
Based on studies of children in Finland who are in daycare or in school, as of 2016, xylitol, administered in chewing gum or a syrup, may have a moderate effect in preventing ear aches in healthy children; whether it can help prevent ear infections in children who are prone to them or who have a respiratory infection is unclear. The EFSA evaluated the claim in 2011, and "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent ear aches.
In 2011, the EFSA approved a marketing claim that foods or beverages containing xylitol or similar sugar replacers cause lower blood glucose and lower insulin responses compared to sugar-containing foods or drinks.
Eating processed foods containing xylitol as a non-nutritive sweetener instead of sugar may be useful to help manage body weight.
Xylitol has no known toxicity in humans. At high doses, xylitol and other polyols cause gastrointestinal discomfort, including flatulence, diarrhea, and irritable bowel syndrome; some people have these adverse effects at lower doses. Xylitol has a lower laxation threshold than some sugar alcohols but is more easily tolerated than mannitol and sorbitol.
In dogs, xylitol (in amounts greater than 100 mg/kg of body weight) generates a rapid, dose-dependent insulin release that can result in hypoglycemia, which can be life-threatening. Low blood sugar can result in a loss of coordination, depression, collapse, and seizures in dogs as quickly as 30 minutes following ingestion. Intake of doses of xylitol greater than 500 to 1000 mg per kilogram body weight has been implicated in potentially fatal liver failure in dogs.
Xylitol has 2.4 kcal/g (10 kJ/mol) of food energy according to US and EU food labeling regulations. Real value varies a bit from this due to many metabolic factors. About 50% of eaten xylitol is not absorbed by the intestines in humans. Instead, 50–75% of this amount is fermented by gut bacteria to short-chain organic acids and gases, which may cause flatulence. The rest of the unabsorbed xylitol is excreted unchanged mostly in feces and less than 2 g of xylitol out of every 100 g ingested is excreted in urine.
About 50% of xylitol is absorbed via intestines. Primarily, the liver metabolizes it. The main metabolic route in humans is: in cytoplasm, nonspecific NAD-dependent dehydrogenase (polyol dehydrogenase) transforms xylitol to D-xylulose. Specific xylulokinase phosphorylates it to D-xylulose-5-phosphate. This then goes to pentose phosphate pathway for further processing.
Sugar rationing during World War II led to an interest in sugar substitutes when interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods.
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