Xylitol is a chemical compound with the formula C 5H 12O 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 freely 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.
Emil Fischer, a German chemistry professor, and his assistant Rudolf Stahel isolated a new compound from beech wood chips in September 1890 and named it Xylit, the German word for xylitol. The following year, the French chemist M.G. Bertrand isolated xylitol syrup by processing wheat and oat straw. Sugar rationing during World War II led to an interest in sugar substitutes. Interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods.
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.
Xylitol is stable enough to be used in baking, but because xylitol and other polyols are more 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, as well as other products 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.
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 less-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 for various oral bacteria to produce insoluble polysaccharides and acid.Streptococcus mutans – a major pathological bacterium – synthesises polysaccharides (glucans) from sucrose to adhere to tooth surfaces. The resultant thick plaque becomes anaerobic and plaque bacteria ferment sugars to produce an acidic environment, dissolving the outer tooth enamel.
Chewing gums containing xylitol and sorbitol may affect caries development. Xylitol-containing chewing gums displayed anticariogenic properties in all protocols, but it was unclear whether this effect was due to increased saliva flow. A Cochrane review suggested a positive anticariogenic effect of xylitol-containing fluoride toothpastes when compared to fluoride-only toothpaste, but there was insufficient evidence to determine whether other xylitol-containing products can prevent caries in infants, children or adults.
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 earache in healthy children – reducing risk of occurrence by 25% – although there is no definitive proof that it could be used as a therapy for earache.
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% 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.
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.
Xylitol is poisonous to 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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