Xylitol is a sugar alcohol used as a sweetener. The name derives from Ancient Greek: ?????, xyl[on], "wood" + suffix -itol, used to denote sugar alcohols. Xylitol is categorized as a polyalcohol or sugar alcohol (specifically an alditol). It has the formula CH2OH(CHOH)3CH2OH. It is a colorless or white solid that is soluble in water. Use of manufactured products containing xylitol may reduce tooth decay.
Video Xylitol
Structure, production, occurrence
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 from xylan, a hemicellulose, which is extracted from hardwoods or corncobs. These polymers can be hydrolyzed into xylose, which are catalytically hydrogenated into xylitol. The conversion changes the sugar (xylose, an aldehyde) into a primary alcohol (xylitol).
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.
Maps Xylitol
Food properties
Xylitol is approved as a food additive in the United States. One gram of xylitol contains 2.43 kilocalories (10.2 kilojoules), or 63% of one gram of sugar (3.87 kcal (16.2 kJ). Xylitol has a glycemic index of 7 (100 for glucose). In some people, xylitol may cause gastrointestinal discomfort, including flatulence, diarrhea, and irritable bowel syndrome. Subjects in one study consumed large monthly amounts of xylitol 1.5 kg (3.3 lb) over two years (maximum daily intake of over 400 g (14 oz), producing gastrointestinal symptoms in some people.
Health aspects
Common products
Xylitol is used as an artificial sweetener in manufactured products, such as drugs or dietary supplements, confections, toothpaste, and chewing gum, but is not a common household sweetener. Xylitol has negligible effects on blood sugar and insulin. Absorbed more slowly than sugar and not supplying calories, it does not influence blood sugar levels.
Dental care
Xylitol is a nonfermentable sugar alcohol which may have advantages in dental care compared to other polyalcohols. Two systematic reviews of clinical trials found no evidence that xylitol was superior to other polyols such as sorbitol or equal to that of topical fluoride in its anti-cavity 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 cavities, 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 preliminary studies compared with chewing sucrose-sweetened gum, xylitol was associated with fewer cavities. Cavity-causing bacteria prefer six-carbon sugars or disaccharides, while xylitol is non-fermentable and is not used as an energy source. This same property renders it unsuitable for making bread as it interferes with the ability of yeast to digest sugars. 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 pH to a neutral range within few minutes of xylitol consumption.
A review of xylitol effects on dental cavities concluded that the body of evidence is of low to very low quality and is insufficient to determine whether any other xylitol-containing products can prevent cavities in infants, older children, or adults.
Weight management
Processed foods containing xylitol as a non-nutritive sweetener may be useful to manage body weight.
Toxicity
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 American Society for the Prevention of Cruelty to Animals (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 to 1000 mg/kg bodyweight) has been implicated in liver failure in dogs, which can be fatal.
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.
See also
- Aspartame
- Birch sap
- L-Xylulose reductase
- Xylonic acid
References
Source of article : Wikipedia
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