Xylitol

Production

Xylitol is produced by hydrogenation of xylose, which converts the sugar (an aldehyde) into a primary alcohol. 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 are Candida tropicalis and Candida guilliermondii.

Properties

One gram of xylitol contains 2.43 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 an extremely low glycemic index of 7 (glucose has a GI of 100).

Dental care

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 which may allow enamel to remineralize before dental cavities form.

Early studies from Finland in the 1970s found, compared with chewing sucrose-sweetened 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 - while still being taken up into the cell (due to similar shape) and 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, in three to five chewing episodes, is thought to be needed for dental efficacy. A source of xylitol that releases it slowly, and a one- to three-minute initial pulse are thought to improve the dental effect.

Xylitol also inhibits the growth of Streptococcus pneumoniae, as well as the attachment of Haemophilus influenzae on the nasopharyngeal cells.

The perception of sweetness obtained from consuming xylitol causes the secretion of saliva which acts as a buffer against the acidic environment created by the microorganisms in dental plaque. Increase in salivation can raise the falling pH to a neutral range 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.

In March, 2015, Cochrane published a review of the entire body of evidence surrounding xylitol's effects on dental caries. Their conclusion was that, while low-quality evidence suggests that over 2.5 to 3 years of use, a fluoride toothpaste containing xylitol may reduce caries when compared to a fluoride-only toothpaste, the remaining body of evidence is of low to very low quality and is insufficient to determine whether any other xylitol-containing products can prevent caries in infants, older children, or adults.

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.

Diabetes

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

In the human gut xylitol is not absorbed as well as glucose or fructose; the unabsorbed xylitol acts as a dietary soluble fiber in helping to maintain certain aspects of gut function. Bacterial fermentation, mainly in the large gut, partly converts xylitol to short-chain fatty acids that the gut can absorb as fuel for energy production in oxidative metabolic pathways. Xylitol also is useful in recovery after heavy exercise because the human body converts absorbed xylitol to glucose 6-phosphate and glycogen. The conversion is however slow, so that the xylitol amounts to a low-GI source of energy.

Ear infection

Xylitol chewing gum appears to decrease rates of acute otitis media in children going to daycare by 25%. Xylitol nasal sprays have also been shown to decrease incidence of acute otitis media as well as being a very effective way of both assisting and stimulating the body's own natural nasopharyngeal washing, and reducing both bacterial colonization and allergenic pollution, with their accompanying problems.

Osteoporosis

A feed containing Xylitol increased bone volume in rat studies conducted in 2001 and 2011, these results have generated interest in the sugar that would examine if it could be a human treatment for osteoporosis.

In humans

Xylitol has no known toxicity in humans, however, some report heart palpitations after consuming it. In one study, participants consumed 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, xylitol has a laxative effect because sugar alcohols are not fully broken down during digestion; however, the effect varies from person to person. In one study of 13 children, four experienced diarrhea from xylitol's laxative effect when they ate more than 65 grams per day. Studies have reported that adaptation occurs after several weeks of consumption.

As with other sugar alcohols, with the exception of erythritol, consumption of xylitol in excess of one's "laxation threshold" (the amount of sweetener that can be consumed before abdominal discomfort occurs) can result in temporary gastrointestinal side effects, such as bloating, flatulence, and diarrhea. Adaptation (that is, 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 mannitol and sorbitol.

In dogs

Xylitol is often fatal 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 eaten 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. The possible cause of hypoglycemia experienced by dogs is that xylitol in chewing gum is released more slowly and absorbed over longer period than when it is consumed as a pure form.

In wild birds

Thirty Cape sugarbirds died within 30 minutes of drinking a solution made with xylitol, from a feeder in a garden in Hermanus, South Africa. It is suspected that it triggered a massive insulin release, causing an irreversible drop in blood sugar.