|Preferred 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|
|NFPA 704 (fire diamond)|
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 chemical compound with the formula C
5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid that is soluble in water. It can be classified as a polyalcohol and a sugar alcohol, specifically an alditol. The name derives from Ancient Greek: ξύλον, xyl[on], "wood", with the suffix -itol used to denote sugar alcohols.
Xylitol is used as a food additive and sugar substitute. Its European Union code number is E967. Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities.
Structure, production, commerce
Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other 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.
According to the US Department of Energy, xylitol production by fermentation from discarded biomass is one of the most valuable renewable chemicals for commerce, forecast to be a US$1.4 billion industry by 2025.
Xylitol is used as a sugar substitute in such manufactured products as drugs, 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. It is approved as a food additive in the United States.
Nutrition, taste, and cooking
Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose.
Xylitol is stable enough to be used in baking, but because xylitol and other polyols are heat stable, they do not caramelise as sugars do. When used in foods, they lower the freezing point of the mixture.
No serious health risk exists in most humans for normal levels of consumption; 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 European Union. Similarly due to a 1985 report, by the E.U. 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".
Xylitol has 2.4 kilocalories of food energy per gram of xylitol (10 kilojoules per gram) according to U.S. and E.U. food-labeling regulations. The real value can vary, depending on metabolic factors.
Primarily, the liver metabolizes absorbed xylitol. The main metabolic route in humans occurs in cytoplasm, via nonspecific NAD-dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol to D-xylulose. Specific xylulokinase phosphorylates it to D-xylulose-5-phosphate. This then goes to pentose phosphate pathway for further processing.
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 by gut bacteria into short-chain organic acids and gases, which may produce flatulence. 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.
Xylitol ingestion also increases motilin secretion, which may be related to xylitol's ability to cause diarrhea. The non-digestible but fermentable nature of xylitol also contributes to constipation relieving effects.
Research has identified carbohydrates, oral bacteria, tooth anatomy, along with their time of interaction as the main pathobiological etiology for dental caries. Sucrose is deemed to be the most cariogenic carbohydrate consumed by humans, as it is a substrate to various oral bacteria to produce insoluble polysaccharides and acid. Streptococcus mutans is a major pathological bacteria. It uses carbohydrates via glycolysis to adhere to tooth surfaces with an extracellular matrix, and produces an acidic environment; that acid dissolves the outer tooth enamel layer of the teeth it adheres to.
Xylitol, a sugar alcohol containing 5 carbon-polyol is metabolized via the phospho-enolpyruvate-phospho-transferase pathway (PEP-PTS) in S. mutans, which produces xylitol-5-phosphate as a product. Xylitol-5-phosphate competes with phosphofructokinase and therefore, results in inhibition of glycolysis via accumulation of glucose-6-phosphate. Over long periods of time of xylitol use, S. mutans are observed to alter their enzymatic activity.
Burt (2006) conducted a systematic review looking at the effect of sugar alcohols on caries activity. His systematic review included randomized controlled trials (RCT) as well as observational studies. Burt concluded that Xylitol displayed non-cariogenic properties in all protocols tested. Interestingly, he also concluded that mothers chewing xylitol-containing gums effectively inhibited the transmission of S. mutans to their offspring. Nayak et al. (2014) also conducted a review where they showed the positive effects of Xylitol in gummy bears, syrups, mouthrinse, dentifrice on inhibiting dental caries. Lastly, Chan et al. (2020) concluded that xylitol has inhibitory effects on S. mutans and Candida albicans. However, other studies, such as one by Muhlemann et al. (1977) seem to call for more research in this area as the results were inconclusive. A Cochrane review conducted in 2015 included 10 studies which displayed a low quality evidence on the effectiveness of xylitol containing fluoride toothpastes when compared to fluoride only toothpaste.
In 2011, EFSA "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent middle-ear infections with a fast onset, which is also known as acute otitis media (AOM). A 2016 review indicated that xylitol in chewing gum or a syrup may have a moderate effect in preventing AOM in healthy children. It may be an alternative to conventional therapies (such as antibiotics) to lower risk of ear aches in healthy children – reducing risk of occurrence by 25% – although there is no definitive proof that it could be used as a therapy for ear aches.
In 2011, 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. Xylitol products are used as sucrose substitutes for weight control, as xylitol has 40 percent fewer calories than sucrose (2.4 kcal/g compared to 4.0 kcal/g for sucrose). The glycemic index (GI) of xylitol is only 7% of the GI for glucose.
When ingested at high doses, xylitol and other polyols may cause gastrointestinal discomfort, including flatulence, diarrhea, and irritable bowel syndrome (see Metabolism above); some people experience the adverse effects at lower doses. Xylitol has a lower laxation threshold than some sugar alcohols but is more easily tolerated than mannitol and sorbitol.
Increased xylitol consumption can increase oxalate, calcium, and phosphate excretion to urine (termed oxaluria, calciuria, and phosphaturia, respectively). These are known risk factors for kidney stone disease, but despite that, xylitol has not been linked to kidney disease in humans.
Dogs and other animals
Xylitol poisons dogs. Ingesting 100 milligrams of xylitol per kilogram of body weight (mg/kg bw) causes dogs to experience a dose-dependent insulin release; depending on the dose it can result in life-threatening hypoglycemia. 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 and ataxia. At doses above 500 mg/kg bw, liver failure is likely and may result in coagulopathies like disseminated intravascular coagulation.
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