Chemistry:Xylitol

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Xylitol is a chemical compound with the formula C5H12O5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid. It is classified as a polyalcohol and a sugar alcohol, specifically an alditol. Of the common sugar alcohols, only sorbitol is more soluble in water. The name derives from Ancient Greek: ξύλον, xyl[on] 'wood', with the suffix -itol used to denote it being a sugar alcohol.

Xylitol is used as a food additive and sugar substitute. Its European Union code number is E967.[1] Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities.[2][3] In the United States, xylitol is used as a common sugar substitute, and is considered to be safe for humans.[4]

Xylitol can be toxic to dogs and ferrets.[5]

History

Emil Fischer, a German chemist, and his assistant Rudolf Stahel isolated a new compound from beech wood chips in September 1890 and named it Xylit, after the Greek word for wood. The following year, the French chemist M. G. Bertrand isolated xylitol syrup by processing wheat and oat straw.[6] 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.[7][8]

Structure, production, commerce

Xylitol is one of three 5-carbon sugar alcohols. The others are arabitol and ribitol. These three compounds differ in the stereochemistry of the three secondary alcohol groups.

5-carbon sugar alcohols

Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts during metabolism of carbohydrates.[7] Unlike most sugar alcohols, xylitol is achiral.[9] 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 mixture is hydrolyzed with acid to give xylose. The xylose is purified by chromatography. Purified xylose is catalytically hydrogenated into xylitol using a Raney nickel catalyst.[10] The conversion changes the sugar (xylose, an aldehyde) into the primary alcohol, xylitol.[7]

Xylitol can also be obtained by industrial fermentation, but this methodology is not as economical as the acid hydrolysis/chromatography route described above. Fermentation is effected by bacteria, fungi, or yeast, especially Candida tropicalis.[7][11] 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 $1.41 billion industry by 2025.[12]

Uses

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.[2][4][13] Xylitol has negligible effects on blood sugar because its assimilation and metabolism are independent of insulin.[13] It is approved as a food additive and sugar substitute in the United States.[4]

Xylitol is also found as an additive to saline solution for nasal irrigation and has been reported to be effective in improving symptoms of chronic sinusitis.[14]

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.[15]

Food properties

Nutrition, taste, and cooking

Humans absorb xylitol more slowly than sucrose, and xylitol supplies 40% fewer calories than an equal mass of sucrose.[13]

Xylitol has about the same sweetness as sucrose,[13] but is sweeter than similar compounds like sorbitol and mannitol.[7]

Xylitol is stable enough to be used in baking,[16] 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.[17]

Food risks

Normal levels of consumption by humans have not been shown to pose serious health risks in most humans. 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 which states 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".[18]

Metabolism

Xylitol has 2.4 kilocalories of food energy per gram (10 kilojoules per gram) according to U.S. and E.U. food-labeling regulations.[19][1] The real value can vary depending on metabolic factors.[20]

The liver primarily metabolizes absorbed xylitol. The main metabolic route in humans occurs in the cytoplasm via nonspecific NAD-dependent dehydrogenase (polyol dehydrogenase), which transforms xylitol to D-xylulose. Specific xylulokinase phosphorylates it to D-xylulose-5-phosphate, which then goes into the pentose phosphate pathway for further processing.[20]

About 50% of ingested xylitol is absorbed via the intestines. In humans, 50–75% of the xylitol not absorbed in the gut is fermented by gut bacteria into short-chain organic acids and gases, potentially leading to flatulence. Any 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.[20]

Xylitol ingestion also increases motilin secretion, which may be related to the ability of xylitol to cause diarrhea.[21] The less-digestible but fermentable nature of xylitol also contributes to constipation-relieving effects.[22]

Health effects

Dental care

A 2015 Cochrane review of ten studies between 1991 and 2014 suggested a positive effect in reducing tooth decay 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 tooth decay in infants, children or adults.[23] Subsequent reviews support the belief that xylitol can suppress the growth of pathogenic Streptococcus in the mouth, thereby reducing dental cavities and gingivitis, although there is concern that swallowed xylitol may cause intestinal dysbiosis.[24][25][26] A 2022 review suggested that xylitol-containing chewing gum decreases plaque, but xylitol-containing candy does not.[27]

Earache

In 2011, EFSA "concluded that there was not enough evidence to support" the claim that xylitol-sweetened gum could prevent middle-ear infections (acute otitis media; AOM).[18][28] A 2016 review indicated that xylitol in chewing gum or a syrup may have a moderate effect in preventing AOM in healthy children.[29] 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%[30] – although there is no definitive proof that it could be used as a therapy for earache.[29]

Diabetes

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.[16][31] Xylitol products are used as sucrose substitutes for weight control,[16][22] as xylitol has 40% fewer calories than sucrose (2.4 kcal/g compared to 4.0 kcal/g for sucrose).[16][32] The glycemic index (GI) of xylitol is only 7% of the GI for glucose.[33]

Adverse effects

Humans

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.[18][34] Xylitol has a lower laxation threshold than some sugar alcohols but is more easily tolerated than mannitol and sorbitol.[35]

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.[36]

Dogs and other animals

Xylitol is poisonous to dogs.[37] 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.[38] It is also poisonous to ferrets.[39]

Xylitol is safe for rhesus macaques, horses, and rats.[38]

A 2018 study suggests that xylitol is safe for cats in doses of up to 1000 mg/kg; however, this study was performed on only 6 cats and should not be considered definitive.[40] The American Society for the Prevention of Cruelty to Animals has never issued any warning about xylitol and cats. A 2022 article by the organisation explicitly lists xylitol as non-toxic.[41]

See also

References

  1. ↑ 1.0 1.1 "Food legislation". European Association of Polyol Producers. 22 March 2017. http://polyols-eu.org/legislation/food/. 
  2. ↑ 2.0 2.1 Riley, P.; Moore, D.; Ahmed, F.; Sharif, M.O.; Worthington, H.V. (26 March 2015). "Xylitol-containing products for preventing dental caries in children and adults". The Cochrane Database of Systematic Reviews 2015 (3). doi:10.1002/14651858.CD010743.pub2. PMID 25809586. 
  3. ↑ Riley, P.; Moore, D.; Ahmed, F.; Sharif, M. O.; Worthington, H. V. (2015). "Can xylitol – used in products like sweets, candy, chewing gum, and toothpaste – help prevent tooth decay in children and adults?". The Cochrane Database of Systematic Reviews. Lay summary 2015 (3). doi:10.1002/14651858.CD010743.pub2. PMID 25809586. PMC 9345289. https://www.cochrane.org/CD010743/ORAL_can-xylitol-used-in-products-like-sweets-candy-chewing-gum-and-toothpaste-help-prevent-tooth-decay-in-children-and-adults. Retrieved 28 October 2018.  open access
  4. ↑ 4.0 4.1 4.2 "Aspartame and Other Sweeteners in Food". US Food and Drug Administration. 14 July 2023. https://www.fda.gov/food/food-additives-petitions/aspartame-and-other-sweeteners-food. 
  5. ↑ "Paws off xylitol; It's dangerous for dogs". US Food and Drug Administration. 7 July 2021. https://www.fda.gov/consumers/consumer-updates/paws-xylitol-its-dangerous-dogs. 
  6. ↑ "The rocky road of xylitol to its clinical application". Journal of Dental Research 79 (6): 1352–5. June 2000. doi:10.1177/00220345000790060101. PMID 10890712. https://journals.sagepub.com/doi/10.1177/00220345000790060101?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Ur-Rehman, S.; Mushtaq, Z.; Zahoor, T.; Jamil, A.; Murtaza, M.A. (2015). "Xylitol: A review on bio-production, application, health benefits, and related safety issues". Critical Reviews in Food Science and Nutrition 55 (11): 1514–1528. doi:10.1080/10408398.2012.702288. PMID 24915309. 
  8. ↑ Hicks, Jesse (Spring 2010). "The pursuit of sweet". Science History (Science History Institute). https://www.sciencehistory.org/distillations/magazine/the-pursuit-of-sweet. Retrieved 28 October 2018. 
  9. ↑ Wrolstad, Ronald E. (2012). Food Carbohydrate Chemistry. John Wiley & Sons. p. 176. ISBN 978-0-8138-2665-3. https://books.google.com/books?id=gVB8l8ukYPYC&pg=PA176. Retrieved 20 October 2012. 
  10. ↑ Schiweck, Hubert; Bär, Albert; Vogel, Roland; Schwarz, Eugen; Kunz, Markwart; Dusautois, Cécile; Clement, Alexandre; Lefranc, Caterine et al. (2012). "Sugar Alcohols". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a25_413.pub3. ISBN 978-3-527-30385-4. 
  11. ↑ Jain, H.; Mulay, S. (March 2014). "A review on different modes and methods for yielding a pentose sugar: Xylitol". International Journal of Food Sciences and Nutrition 65 (2): 135–143. doi:10.3109/09637486.2013.845651. PMID 24160912. 
  12. ↑ Felipe Hernández-Pérez, Andrés; de Arruda, Priscila Vaz; Sene, Luciane; da Silva, Silvio Silvério; Kumar Chandel, Anuj; de Almeida Felipe, Maria das Graças (16 July 2019). "Xylitol bioproduction: State-of-the-art, industrial paradigm shift, and opportunities for integrated biorefineries". Critical Reviews in Biotechnology 39 (7): 924–943. doi:10.1080/07388551.2019.1640658. ISSN 0738-8551. PMID 31311338. 
  13. ↑ 13.0 13.1 13.2 13.3 "Xylitol". 2018. https://www.drugs.com/npp/xylitol.html. 
  14. ↑ Weissman, Joshua D.; Fernandez, Francisca; Hwang, Peter H. (November 2011). "Xylitol nasal irrigation in the management of chronic rhinosinusitis: A pilot study". The Laryngoscope 121 (11): 2468–2472. doi:10.1002/lary.22176. ISSN 1531-4995. PMID 21994147. 
  15. ↑ Peng, Yucan; Cui, Yi (15 April 2020). "Advanced Textiles for Personal Thermal Management and Energy" (in en). Joule 4 (4): 724–742. doi:10.1016/j.joule.2020.02.011. ISSN 2542-4351. Bibcode: 2020Joule...4..724P. 
  16. ↑ 16.0 16.1 16.2 16.3 "Xylitol". Diabetes.co.uk. https://www.diabetes.co.uk/sweeteners/xylitol.html. 
  17. ↑ Burgos, Karen; Subramaniam, Persis; Arthur, Jennifer (21 November 2016). "Reformulation guide for small to medium sized companies". Leatherhead Food Research. https://www.fdf.org.uk/corporate_pubs/Reformulation-Guide-Sugars-Aug2016.pdf. 
  18. ↑ 18.0 18.1 18.2 "Is xylitol good for your teeth?". U.K. National Health Service. 13 April 2016. https://www.nhs.uk/live-well/eat-well/is-xylitol-good-for-your-teeth/. 
  19. ↑ Calculation of the Energy Content of Foods (Report). The United Nations. 
  20. ↑ 20.0 20.1 20.2 Livesey, G. (2003). "Health potential of polyols as sugar replacers, with emphasis on low glycaemic properties". Nutrition Research Reviews 16 (2): 163–191. doi:10.1079/NRR200371. ISSN 1475-2700. PMID 19087388. 
  21. ↑ Wölnerhanssen, B. K.; Meyer-Gerspach, A. C.; Beglinger, C.; Islam, M. S. (June 2019). "Metabolic effects of the natural sweeteners xylitol and erythritol: A comprehensive review". Critical Reviews in Food Science and Nutrition 60 (12): 1986–1998. doi:10.1080/10408398.2019.1623757. PMID 31204494. 
  22. ↑ 22.0 22.1 Salli, Krista; Lehtinen, Markus J.; Tiihonen, Kirsti; Ouwehand, Arthur C. (6 August 2019). "Xylitol's health benefits beyond dental health: A comprehensive review". Nutrients 11 (8): 1813. doi:10.3390/nu11081813. ISSN 2072-6643. PMID 31390800. 
  23. ↑ "Xylitol-containing products for preventing dental caries in children and adults". The Cochrane Database of Systematic Reviews 2015 (3). 2015. doi:10.1002/14651858.CD010743.pub2. PMID 25809586. 
  24. ↑ "Health benefits of xylitol". Applied Microbiology and Biotechnology 104 (17): 225–7237. 2020. doi:10.1007/s00253-020-10708-7. PMID 32638045. 
  25. ↑ "Meta-analysis on the Effectiveness of Xylitol in Caries Prevention". Journal of International Society of Preventive & Community Dentistry 12 (2): 133–138. 2022. doi:10.4103/jispcd.JISPCD_164_21. PMID 35462747. 
  26. ↑ "Oral and Systemic Effects of Xylitol Consumption". Caries Research 53 (5): 491–501. 2019. doi:10.1159/000499194. PMID 31060040. 
  27. ↑ Söderling, Eva; Pienihäkkinen, Kaisu (2022). "Effects of xylitol chewing gum and candies on the accumulation of dental plaque: a systematic review". Clinical Oral Investigations 26 (1): 119–129. doi:10.1007/s00784-021-04225-8. ISSN 1432-6981. PMID 34677696. 
  28. ↑ EFSA panel (June 2011). "Scientific opinion on the substantiation of health claims related to sugar-free chewing gum sweetened with xylitol and plaque acid neutralisation (ID 485), maintenance of tooth mineralisation (ID 486, 562, 1181), reduction of dental plaque (ID 485, 3085)". EFSA Journal 9 (6): 2266. doi:10.2903/j.efsa.2011.2266. 
  29. ↑ 29.0 29.1 Azarpazhooh, A.; Lawrence, H.P.; Shah, P.S. (3 August 2016). "Xylitol for preventing acute otitis media in children up to 12 years of age". The Cochrane Database of Systematic Reviews 2016 (8). doi:10.1002/14651858.CD007095.pub3. PMID 27486835. 
  30. ↑ Marom, Tal; Marchisio, Paola; Tamir, Sharon Ovnat; Torretta, Sara; Gavriel, Haim; Esposito, Susanna (12 February 2016). "Complementary and alternative medicine treatment options for otitis media". Medicine 95 (6). doi:10.1097/MD.0000000000002695. ISSN 0025-7974. PMID 26871802. 
  31. ↑ EFSA panel (April 2011). "Scientific opinion on the substantiation of health claims related to the sugar replacers xylitol, sorbitol, mannitol, maltitol, lactitol, isomalt, erythritol, D-tagatose, isomaltulose, sucralose and polydextrose and maintenance of tooth mineralisation by decreasing tooth demineralisation, and reduction of post-prandial glycaemic responses". EFSA Journal 9 (4): 2076. doi:10.2903/j.efsa.2011.2076. 
  32. ↑ Tiefenbacher, Karl F. (2017). "Technology of Main Ingredients – Sweeteners and Lipids". Wafer and Waffle. Elsevier. pp. 123–225. doi:10.1016/b978-0-12-809438-9.00003-x. ISBN 978-0-12-809438-9. 
  33. ↑ Foster-Powell, K.; Holt, S.H.; Brand-Miller, J.C. (July 2002). "International table of glycemic index and glycemic load values: 2002". The American Journal of Clinical Nutrition 76 (1): 5–56. doi:10.1093/ajcn/76.1.5. PMID 12081815. 
  34. ↑ Mäkinen, Kauko (20 October 2016). "Gastrointestinal disturbances associated with the consumption of sugar alcohols with special consideration of xylitol: Scientific review and instructions for dentists and other health-care professionals". International Journal of Dentistry 2016. doi:10.1155/2016/5967907. PMID 27840639. 
  35. ↑ Sugar Alcohols (Report). Canadian Diabetes Association. 1 May 2005. http://www.dm2nb.ca/pdf/patient_resources/diabetes/sugar_alcohols_cda.pdf. Retrieved 14 March 2012. 
  36. ↑ Janket, S.; Benwait, J.; Isaac, P.; Ackerson, L.K.; Meurman, J.H. (2019). "Oral and systemic effects of xylitol consumption". Caries Research 53 (5): 491–501. doi:10.1159/000499194. PMID 31060040. 
  37. ↑ "Paws off xylitol; It's dangerous for dogs". US Food and Drug Administration. 7 July 2021. https://www.fda.gov/consumers/consumer-updates/paws-xylitol-its-dangerous-dogs. 
  38. ↑ 38.0 38.1 Schmid, R. D.; Hovda, L. R. (2016). "Acute hepatic failure in a dog after xylitol ingestion". Journal of Medical Toxicology 12 (2): 201–205. doi:10.1007/s13181-015-0531-7. PMID 26691320. 
  39. ↑ "FDA warns of xylitol dangers to dogs, ferrets". 15 April 2011. https://www.avma.org/javma-news/2011-04-15/fda-warns-xylitol-dangers-dogs-ferrets. 
  40. ↑ Jerzsele, Á.; Karancsi, Z.; Pászti-Gere, E.; Sterczer, Á.; Bersényi, A.; Fodor, K.; Szabó, D.; Vajdovich, P. (2018). "Effects of p.o. administered xylitol in cats". Journal of Veterinary Pharmacology and Therapeutics 41 (3): 409–414. doi:10.1111/jvp.12479. PMID 29430681. 
  41. ↑ Bershadker, Matt (22 March 2022). "Matt's Blog: Be Prepared to Deal with Pet Poisons" (in en). https://www.aspca.org/blog/matts-blog-be-prepared-deal-pet-poisons. 



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