 | |
 Xylitol crystals | |
| Names | |
|---|---|
| Pronunciation | /ˈzaɪlɪtɒl/ |
| IUPAC name meso-Xylitol | |
| Systematic IUPAC name (2R,3r,4S)-Pentane-1,2,3,4,5-pentol | |
Other names
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| Identifiers | |
| |
3D model (JSmol) | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.001.626 |
| E number | E967(glazing agents, ...) |
| KEGG | |
| UNII | |
| |
| |
| Properties | |
| C5H12O5 | |
| Molar mass | 152.146 g·mol−1 |
| Density | 1.52 g/cm3 |
| 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[2] |
| 168 g/100 g[3] | |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Relatedalkanes | Pentane |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Xylitol is achemical compound with the formulaC
5H
12O
5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particularstereoisomer with that structural formula. It is a colorless or whitecrystalline solid. It is classified as apolyalcohol and asugar alcohol, specifically analditol. Of the common sugar alcohols, onlysorbitol is more soluble in water.
The name derives fromAncient Greek:ξύλον,xyl[on] 'wood', with the suffix-itol used to denote it being a sugar alcohol.
Xylitol is used as afood additive andsugar substitute. ItsEuropean Union code number isE967.[4] Replacingsugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself preventsdental cavities.[5][6] In the United States, xylitol is used as a commonsugar substitute, and is considered to be safe for humans.[7]
Xylitol can be toxic todogs.[8]
Emil Fischer, a German chemist, and his assistant Rudolf Stahel isolated a new compound frombeech wood chips in September 1890 and named itXylit, after the Greek word for wood. The following year, the French chemist M. G. Bertrand isolated xylitol syrup by processing wheat and oat straw.[9] Sugar rationing duringWorld War II led to an interest insugar substitutes. Interest in xylitol and other polyols became intense, leading to theircharacterization and manufacturing methods.[10][11]
Xylitol is one of three 5-carbon sugar alcohols. The others arearabitol andribitol. These three compounds differ in the stereochemistry of the three secondary alcohol groups.
Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts duringmetabolism ofcarbohydrates.[10] Unlike most sugar alcohols, xylitol isachiral.[12] Most otherisomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has a plane of symmetry.
Industrial production starts withlignocellulosic biomass from whichxylan is extracted; raw biomass materials includehardwoods,softwoods, and agricultural waste from processing maize, wheat, or rice. The mixture is hydrolyzed with acid to givexylose. The xylose is purified bychromatography. Purifiedxylose is catalyticallyhydrogenated into xylitol using aRaney nickel catalyst.[3] The conversion changes the sugar (xylose, analdehyde) into theprimary alcohol, xylitol.[10]
Xylitol can also be obtained byindustrial fermentation, but this methodology are not as economical as the acid hydrolysis/chromatography route described above. Fermentation is effected by bacteria, fungi, or yeast, especiallyCandida tropicalis.[10][13] According to the USDepartment of Energy, xylitol production byfermentation from discardedbiomass is one of the most valuablerenewable chemicals for commerce, forecast to be a US $1.41 billion industry by 2025.[14]
Xylitol is used as a sugar substitute in such manufactured products asdrugs,dietary supplements,confections,toothpaste, andchewing gum, but is not a common household sweetener.[5][7][15] Xylitol has negligible effects onblood sugar because its assimilation and metabolism are independent ofinsulin.[15] It is approved as a food additive and sugar substitute in the United States.[7]
Xylitol is also found as an additive tosaline solution fornasal irrigation and has been reported to be effective in improving symptoms of chronicsinusitis.[16]
Xylitol can also be incorporated into fabrics to produce a cooling fabric. When moisture, such as sweat, comes into contact with the xylitol embedded in the fabric, it produces a cooling sensation.[17]
Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose.[15]
Xylitol has about the same sweetness assucrose,[15] but is sweeter than similar compounds likesorbitol andmannitol.[10]
Xylitol is stable enough to be used in baking,[18] but because xylitol and other polyols are more heat-stable, they do notcaramelise as sugars do. When used in foods, they lower the freezing point of the mixture.[19]
No serious health risk exists in most humans for normal levels of consumption. TheEuropean Food Safety Authority has not set a limit on daily intake of xylitol. Due to the adverselaxative effect that all polyols have on the digestive system in high doses, xylitol is banned from soft drinks in theEuropean Union. Similarly, due to a 1985 report by the E.U.Scientific Committee on Food which states that "ingesting 50 g a day of xylitol can causediarrhea", tabletop sweeteners (as well as other products containing xylitol) are required to display the warning "Excessive consumption may induce laxative effects".[20]
Xylitol has 2.4 kilocalories offood energy per gram of xylitol (10 kilojoules per gram) according toU.S. andE.U. food-labeling regulations.[21][4] The real value can vary, depending on metabolic factors.[22]
Primarily, the liver metabolizes absorbed xylitol. The main metabolic route in humans occurs incytoplasm, via nonspecificNAD-dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol toD-xylulose. Specificxylulokinase phosphorylates it toD-xylulose-5-phosphate. This then goes topentose phosphate pathway for further processing.[22]
About 50% of eaten xylitol is absorbed via the intestines. Of the remaining 50% that is not absorbed by the intestines, in humans, 50–75% of the xylitol remaining in the gut is fermented bygut bacteria into short-chain organic acids and gases, which may produceflatulence. The remnant unabsorbed xylitol that escapes fermentation is excreted unchanged, mostly in feces; less than 2 g of xylitol out of every 100 g ingested is excreted via urine.[22]
Xylitol ingestion also increasesmotilin secretion, which may be related to xylitol's ability to cause diarrhea.[23] The less-digestible but fermentable nature of xylitol also contributes to constipation relieving effects.[24]
A 2015Cochrane review of ten studies between 1991 and 2014 suggested a positive effect in reducingtooth decay of xylitol-containingfluoride toothpastes when compared to fluoride-only toothpaste, but there was insufficient evidence to determine whether other xylitol-containing products can prevent tooth decay in infants, children or adults.[25] Subsequent reviews support the belief that xylitol can suppress the growth of pathogenicStreptococcus in the mouth, thereby reducing dental caries andgingivitis, although there is concern that swallowed xylitol may causeintestinal dysbiosis.[26][27][28] A 2022 review suggested that xylitol-containingchewing gum decreases plaque, but not xylitol-containing candy.[29]
In 2011EFSA "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent middle-ear infections, also known asacute otitis media (AOM).[20][30] A 2016 review indicated that xylitol in chewing gum or a syrup may have a moderate effect in preventing AOM in healthy children.[31] It may be an alternative to conventional therapies (such asantibiotics) to lower risk of earache in healthy children – reducing risk of occurrence by 25%[32] – although there is no definitive proof that it could be used as a therapy for earache.[31]
In 2011, EFSA approved a marketing claim that foods or beverages containing xylitol or similar sugar replacers cause lower blood glucose and lowerinsulin responses compared to sugar-containing foods or drinks.[18][33] Xylitol products are used assucrose substitutes for weight control,[18][24] as xylitol has 40% fewer calories than sucrose (2.4 kcal/g compared to 4.0 kcal/g for sucrose).[18][34] Theglycemic index (GI) of xylitol is only 7% of the GI forglucose.[35]
When ingested at high doses, xylitol and other polyols may causegastrointestinal discomfort, includingflatulence,diarrhea, andirritable bowel syndrome (seeMetabolism above); some people experience the adverse effects at lower doses.[20][36] Xylitol has a lowerlaxation threshold than somesugar alcohols but is more easily tolerated thanmannitol andsorbitol.[37]
Increased xylitol consumption can increase oxalate, calcium, and phosphate excretion to urine (termedoxaluria,calciuria, andphosphaturia, respectively). These are known risk factors forkidney stone disease, but despite that, xylitol has not been linked to kidney disease in humans.[38] A 2024 study suggests that xylitol is prothrombotic (increases clotting) and is associated with cardiovascular risk when consumed at "typical dietary amounts".[39]
Xylitol is poisonous todogs.[8] Ingesting 100 milligrams of xylitol per kilogram of body weight (mg/kg bw) causes dogs to experience a dose-dependentinsulin release; depending on the dose it can result in life-threateninghypoglycemia. Hypoglycemic symptoms of xylitol toxicity may arise as quickly as 30 to 60 minutes after ingestion. Vomiting is a common first symptom, which can be followed by tiredness andataxia. At doses above 500 mg/kg bw,liver failure is likely and may result incoagulopathies likedisseminated intravascular coagulation.[40]
Xylitol is safe forrhesus macaques,horses, andrats.[40]
A 2018 study suggests that xylitol is safe forcats in doses of up to 1000 mg/kg; however, this study was performed on only 6 cats and should not be considered definitive.[41]
Media related toXylitol at Wikimedia Commons
