|Jmol-3D images||Image 1|
|Molar mass||152.15 g mol−1|
|Melting point||92–96 °C|
|Boiling point||216 °C|
|Solubility in water||~ 1.5 g/mL|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C or 77 °F, 100 kPa)
Xylitol (//; Greek: ξύλον, xyl[on], "wood" + suffix -itol, used to denote sugar alcohols), categorized as a polyalcohol or sugar alcohol (alditol), has applications in hygiene and nutraceutical formulations and products. Xylitol has the formula (CHOH)3(CH2OH)2 and is an achiral isomer of pentane-1,2,3,4,5-pentol. Xylitol is used as a diabetic sweetener which is roughly as sweet as sucrose with 33% fewer calories. Unlike other natural or synthetic sweeteners, xylitol is actively beneficial for dental health by reducing caries to a third in regular use and helpful to remineralization. Multiple studies utilizing electron microscopy have indicated that xylitol is effective in inducing remineralization of deeper layers of demineralized enamel. Xylitol also has been shown to reduce the incidence of acute middle ear infection.
Xylitol is naturally found in low concentrations in the fibers of many fruits and vegetables, and can be extracted from various berries, oats, and mushrooms, as well as fibrous material such as corn husks and sugar cane bagasse, and birch. However, industrial production starts from xylan (a hemicellulose) extracted from hardwoods or corncobs, which is hydrolyzed into xylose and catalytically hydrogenated into xylitol.It was found that xylitol is one of the better artificial sweeteners than chemically originated artificially sweeteners because it has reduced or nonexistent side effects, low calorific value, and low cariogenicity compared to sucrose. 
Xylitol was discovered almost simultaneously by German and French chemists in the late 19th century, and was first popularized in Europe as a safe sweetener for people with diabetes that would not affect insulin levels. Xylitol is produced by hydrogenation of xylose, which converts the sugar (an aldehyde) into a primary alcohol. It can also be extracted from natural sources and is often harvested by tapping birch trees to produce birch sap. Another method of producing xylitol is through microbial processes, including fermentative and biocatalytic processes in bacteria, fungi, and yeast cells, that take advantage of the xylose-intermediate fermentations to produce high yield of xylitol.  Common yeast cells used in effectly fermenting and producing xylitol is Candida tropicalis and Candida guilliermondii.  Its dental significance was researched in Finland in the early 1970s. There, scientists at Turku University demonstrated dental benefits in what became known as the "Turku sugar studies".
One gram of xylitol contains 2.4 kilocalories (kcal), as compared to one gram of sugar, which has 3.87 kcal. Xylitol has virtually no aftertaste, and is advertised as "safe for diabetics and individuals with hyperglycemia." This tolerance is attributed to the lower effect of xylitol on a person's blood sugar, compared to that of regular sugars as it has a very low glycemic index of 7 (glucose has a GI of 100). Xylitol has no known toxicity or carcinogenicity, and is considered safe by the U.S. FDA
Xylitol is a “tooth-friendly”, nonfermentable sugar alcohol. It appears to have more dental health benefits than other polyalcohols. The structure of xylitol contains a tridentate ligand, (H-C-OH)3 that can rearrange with polyvalent cations like Ca2+. This interaction allows Ca2+ to be transported through the gut wall barrier and through saliva may remineralize enamel before dental caries form.
Early studies from Finland in the 1970s found compared to chewing sucrose-flavored gum, xylitol resulted in nearly two fewer cavities or missing teeth. Cavity-causing bacteria prefer six-carbon sugars or disaccharides, while xylitol is non-fermentable and cannot be used as an energy source, interfering with bacterial growth and reproduction. The harmful micro-organisms are starved in the presence of xylitol, allowing the mouth to remineralize damaged teeth with less interruption. This same property renders it unsuitable for making bread as it interferes with the ability of yeast to digest sugars. At least six grams of xylitol per day is thought to be needed for dental efficacy.
The perception of sweetness obtained from consuming xylitol initiates the body to secrete saliva that acts as a buffer system against the acidic environment created by the microorganisms in the dental plaque. Increase in salivary pH can raise the falling pH to its neutral pH within few minutes of xylitol consumption.
However, despite these promising conjectures two systematic reviews of clinical trials could not find conclusive evidence that xylitol was indeed superior to other polyols such as sorbitol or equal to that of topical fluoride in its anti-caries effect.
In the 33-month Xylitol for Adult Caries Trial, participants were given lozenges of either five grams of xylitol or a sucralose-sweetened placebo. While this study initially found no statistically-significant reduction in 33-month caries increment among adults at an elevated risk of developing caries, a further examination of data from this study revealed a significant reduction in the incidence of root caries in the group that received xylitol.
Xylitol is categorized by the U.S. Food and Drug Administration as a food additive. Like other sugar alcohol-sweetened products, xylitol-sweetened products are allowed to be labeled with the claim that they do not promote dental cavities.
Possessing approximately 33% fewer calories, xylitol is a lower-calorie alternative to table sugar. Absorbed more slowly than sugar, it does not contribute to high blood sugar levels or the resulting hyperglycemia caused by insufficient insulin response. This characteristic has also proven beneficial for people suffering from metabolic syndrome, a common disorder that includes insulin resistance, hypertension, hypercholesterolemia, and an increased risk for blood clots. Xylitol is used as a sweetener in medicines, chewing gum and pastilles.
Source of energy
Xylitol consumed is absorbed incompletely and some that are unabsorbed can be used as a dietary fiber in helping to maintain gut function that consequently uses bacterial fermentation to convert xylitol to short fatty acid chains that can be utilized in energy pathways. Xylitol is also useful in recovery after heavy exercise because of its ability to efficiently convert to glucose and glycogen. 
Ear and upper respiratory infections
Studies have shown xylitol chewing gum can help prevent acute otitis media the act of chewing and swallowing assists with the disposal of earwax and clearing the middle ear, while the presence of xylitol prevents the growth of bacteria in the eustachian tubes (auditory or pharyngotympanic tubes) which connect the nose and ear. When bacteria enter the body, they adhere to the tissues using a variety of sugar complexes. The open nature of xylitol and its ability to form many different sugar-like structures appears to interfere with the ability of many bacteria to adhere. In a double-blind, randomized, controlled trial, saline solutions of xylitol significantly reduced the number of nasal coagulase-negative Staphylococcus bacteria. The researchers attributed the benefits to the increased effectiveness of endogenous antimicrobial factors. In a very small case series, nasally administered xylitol reduced ear complaints in children previously having chronic complaints, on the order of almost one a month, by more than 92%. The author also reported beneficial effects on asthma with nasal administration.
Xylitol has no known toxicity in humans. In one study, the participants consumed a diet containing a monthly average of 1.5 kg of xylitol with a maximum daily intake of 430 g with no apparent ill effects. Like most sugar alcohols, it has a laxative effect because sugar alcohols are not fully broken down during digestion; albeit one-tenth the strength of sorbitol.[clarification needed] The effect depends upon the individual. In one study of 13 children, four experienced diarrhea when consuming over 65 grams per day. Studies have reported adaptation occurs after several weeks of consumption.
As with other sugar alcohols, with the exception of erythritol, consumption in excess of one's laxation threshold (the amount of sweetener that can be consumed before abdominal discomfort sets in) can result in temporary gastrointestinal side effects, such as bloating, flatulence, and diarrhea. Adaptation, an increase of the laxation threshold, occurs with regular intake. Xylitol has a lower laxation threshold than some sugar alcohols, but is more easily tolerated than others such as mannitol and sorbitol.
Xylitol is well established as a life-threatening toxin to dogs. According to the ASPCA Animal Poison Control Center, the number of cases of xylitol toxicosis in dogs has significantly increased since the first reports in 2002. Dogs that have ingested foods containing xylitol (greater than 100 milligrams of xylitol consumed per kilogram of bodyweight) have presented with low blood sugar (hypoglycemia), which can be life-threatening. Low blood sugar can result in a loss of coordination, depression, collapse and seizures in as little as 30 minutes. Intake of doses of xylitol (greater than 500 – 1000 mg/kg bwt) has been implicated in liver failure in dogs, which can be fatal. Possible cause of hypoglycemia experienced by dogs is the fact that the xylitol in gum is released more slowly and absorbed over longer period than when it is consumed as a pure form. 
Notes and references
- Material safety data sheet for xylitol from Fisher Scientific. Retrieved on 2013-02-23.
- Wrolstad, Ronald E. (2012). Food Carbohydrate Chemistry. John Wiley & Sons. p. 176. ISBN 9780813826653. Retrieved October 20, 2012. "Xylitol contains asymmetric carbon atoms, but it is not chiral because the molecule as a whole is symmetrical."
- Steinberg, LM; Odusola, F; Mandel, ID (1992 Sep-Oct). "Remineralizing potential, antiplaque and antigingivitis effects of xylitol and sorbitol sweetened chewing gum.". Clinical preventive dentistry 14 (5): 31–4. PMID 1291185. Retrieved 13 November 2013.
- Azarpazhooh, A.; Limeback, H.; Lawrence, H. P.; Shah, P. S. (2011). Xylitol for preventing acute otitis media in children up to 12 years of age. In Azarpazhooh, Amir. "Cochrane Database of Systematic Reviews". Cochrane database of systematic reviews (Online) (11): CD007095. doi:10.1002/14651858.CD007095.pub2. PMID 22071833.
- Gare, Fran (February 1, 2003). The Sweet Miracle of Xylitol. Basic Health Publications, Inc. ISBN 1-59120-038-5.
- Rao, R. Sreenivas; Jyothi, Ch. Pavana; Prakasham, RS; Sharma, PN; Rao, L. Venkateswar (2006). "Xylitol production from corn fiber and sugarcane bagasse hydrolysates by Candida tropicalis". Bioresource Technology 97 (15): 1974–1978. doi:10.1016/j.biortech.2005.08.015. PMID 16242318. Retrieved March 14, 2012.
- "FAQ". Xylitol Canada. Retrieved March 14, 2012.
- Converti, Atillio; Parego, Patrizia; Dominguez, Jose Manuel (1999). "Xylitol Production from Hardwood Hemicellulose Hydrosylates". Applied Biochemistry and Biotechnology 82: 141–151.
- Islam, Shahidul; Indrajit, M. (2012). "Effects of Xylitol on Blood Glucose, Glucose Tolerance, Serum Insulin and Lipid Profile in a Type 2 Diabetes Model of Rats". Ann. Nutr. Metab. 61: 57-64.
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- Barbosa,, M.F.S.; de Medeiros, M.B.; de Manchilha, I.M.; Schneider, H.; Lee, H. (1988). "Screening of yeasts for production of xylitol from D-xylose and some factors which affect xylitol yield in Candida guillermondii". J. Indust. Microbiol. 3: 241-251.
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- "Sugars, granulated (sucrose)". Self Nutrition Data. Retrieved March 14, 2012. With a serving size of 100 grams, there are 387 calories.
- The American Journal of Clinical Nutrition, January 1, 2002: International table of glycemic index and glycemic load values Retrieved 2012-08-26
- Edwardsson, Stig; Birkhed, Dowen; Mejàre, Bertil (1977). "Acid production from Lycasin, maltitol, sorbitol and xylitol by oral streptococci and lactobacilli". Acta Odontologica Scandinavica 35 (5): 257–263. doi:10.3109/00016357709019801. PMID 21508.
- Drucker, D.B.; Verran, J. (1979). "Comparative effects of the substance-sweeteners glucose, sorbitol, sucrose, xylitol and trichlorosucrose on lowering of pH by two oral Streptococcus mutans strains in vitro". Archives of Oral Biology 24 (12): 965–970. doi:10.1016/0003-9969(79)90224-3. PMID 44996.
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- Remacle, Claude; Reusens, Brigitte, ed. (2004). Functional foods, ageing and degenerative disease. Cambridge, England: Woodhead Publishing. p. 202. ISBN 978-1-85573-725-9. Retrieved March 14, 2012.
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- Scheinin, Arje (1993). "Dental Caries, Sugars and Xylitol". Ann Med 25: 519-521.
- Mickenautsch, Steffen; Yengopal, Veerasamy (2012). "Effect of xylitol versus sorbitol: A quantitative systematic review of clinical trials". International Dental Journal 62 (4): 175–88. doi:10.1111/j.1875-595X.2011.00113.x. PMID 23016999.
- Mickenautsch, Steffen; Yengopal, Veerasamy (2012). "Anticariogenic effect of xylitol versus fluoride - a quantitative systematic review of clinical trials". International Dental Journal 62 (1): 6–20. doi:10.1111/j.1875-595X.2011.00086.x. PMID 22251032.
- Bader, James D., et al. (Jan. 2013). "Results from the Xylitol for Adult Caries Trial (X-ACT)". The Journal of the American Dental Association 144 (1): 21–30.
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- Mäkinen, KK (1976). "Long-term tolerance of healthy human subjects to high amounts of xylitol and fructose: general and biochemical findings". Internationale Zeitschrift fur Vitamin und Ernahrungsforschung Beiheft 15: 92–104. PMID 783060.
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- Dunayer, Erik K. (December 2006). "New findings on the effects of xylitol ingestion in dogs". Veterinary Medicine 101 (12): 791–797. Retrieved March 14, 2012.
- Dunayer, Eric K (2004). "Hypoglycemia Following Canine Ingestion of Xylitol-Containing Gum". Vet. Human Toxicol. 46 (2): 87-88.