Xylitol is a white crystalline substance similar in appearance to sugar with a much sweeter taste but approximately one-third fewer calories. It is extracted from xylan, with the main sources obtained from beech and birch hardwood barks and corn cobs. It is also found in rice, straw, oat, wheat and cotton seed hulls, various nut shells, fruits (plums, strawberries, raspberries), vegetables (mushrooms, endive, cauliflower), and naturally produced, to some degree, in the human body.
Xylitol quickly dissolves with a refreshing, cooling sensation. As a polyol, it is absorbed slowly and incompletely from the small intestines into the blood. Little or no insulin is metabolised during the absorption process. Any remaining portions of xylitol in the blood are broken down in the large intestines. Chemically, it is a 5-carbon sugar alcohol (preventing the growth of bacteria or an alkaline enhancement) compared to sugar, which is a 6-carbon sugar alcohol (promotes bacteria and fungi growth and is acid-forming) (Sellman S, 2003; Ashley D, Barbieri S 2005).
Caries control
Briefly stated, bacteria (Streptococcus mutans) are located in the biofilm on tooth surfaces and form a sticky environment. S. mutans metabolise the sugars (fermentable carbohydrates) entering the mouth, causing the sugars to metabolise into lactic acids. The acids create a lower pH level, thus demineralising the tooth surface, which ultimately leads to caries formation. When xylitol is present, S. mutans are attracted to the xylitol over other sugars. The bacteria cannot metabolise xylitol, causing a disruption in their protein synthesis. This results in a decrease in the number of S. mutans and, as a result, the pH level returns to homeostasis (Gutkowski S, 2005).
Xylitol may contribute to dental decay reduction via:
• The reduction of S. mutans in plaque and saliva
• The interruption of acid production
• The reduction of plaque accumulation
• The support of the remineralisation process of tooth enamel (Maguire A, Rugg-Gunn AJ, 2003; Phipps K, Bruerd B, 2004).
The most effective mode of administration is to chew gum containing xylitol. Recommended dosages range from 6g to 10g of xylitol daily, three to five times per day, for five minutes each time (Phipps K, Bruerd B, 2004; Richter P, Chaffin J, 2004).
Research
Between 1982 and 1984, the Ylivieska study enrolled 258 children aged 11 and 12 years old who chewed 7g to 10g of xylitol gum daily, which resulted in a 30% to 60% reduction in new decay (Isokangas P et al, 1988). Five years later, the authors re-examined the children and the participants still experienced a 55% reduction in the rate of caries (Isokangas P et al, 1993).
The Belize study, from 1989 to 1993, was a comprehensive 40-month study that used 1,277 subjects who were separated into nine groups, with each group chewing one type of gum (Makinen KK, Bennett CA, Hujoel PP et al, 1995; Makinen KK, Makinen PL, Pape HR Jr et al, 1995). The authors concluded that regular use of polyol-based chewing gum reduced caries rates in young children, with xylitol being the most effective sugar substitute. The Belize study re-examined the subjects five years later and found significant reductions in caries even after the use of xylitol had ended (Makinen KK, Hujoel PP, Bennett CA et al, 1998). Both the Ylivieska and Belize studies suggest the value of xylitol during tooth eruption.
Hayes reviewed 14 clinical studies, dated from 1966 to 2001, which featured the use sugar substitutes, xylitol and sorbitol. Hayes was looking for a reduction in dental caries outside of the United States, and the studies consistently displayed 30% to 60% reduction in dental caries from using xylitol chewing gum or toothpaste. The highest decay rate reductions were found in subjects using xylitol (Hayes C, 2001).
Benefits beyond oral health
Xylitol may not only be useful in caries reduction; new benefits are being discovered that may aid patients ranging from children with acute otitis media (AOM) to elderly people with candidiasis.
Finnish researchers studied 306 children in daycare nurseries with histories of repeated AOM. Half of the children chewed xylitol-sweetened gum after all meals and snacks (two pieces, five times per day for two months) and half of the children chewed regular gum.
The incidence of AOM in xylitol chewers (12%) dropped by almost half compared to regular gum chewers (21%) (Uhari M, Kontiokari T, Niemela M, 1998).
Some AOM may have been prevented through the swallowing that accompanies chewing gum, which automatically helps to clear the middle ear canal. Since chewing of xylitol gum indicated a decrease in alpha-haemolytic streptococci for AOM, this same theory could possibly hold true for reducing sinus infections, as similar streptococcal are involved.
In a three-month Finnish study on AOM, 857 healthy day care centre children were randomised into five treatment groups. The groups included a control syrup, xylitol syrup, control chewing gum, xylitol gum and xylitol lozenge. Results indicated AOM incidences were lower in children who had received xylitol lozenge (20% decrease), xylitol syrup (30% decrease) and xylitol gum (40% decrease) with less need for antimicrobials in the control group children.
Xylitol appeared to result in a local inhibitory action with pneumococci and H. influenzae (Uhari M, Kontiokari T, Niemela M, 1998; Hujoel PP, Makinen KK, Bennett CA et al, 1999), however the actual health impact of the inhibition is unknown.
Diabetes management has three major goals: to control blood glucose, lipids and weight. Xylitol is absorbed slowly in the body, so the rise in blood glucose and insulin needed to metabolise glucose is greatly reduced. It is possible that oral consumption will not increase blood glucose levels.
Xylitol’s caloric value of 2.4 calories per gram versus 4.0 for sugar has the potential to aid in weight control for individuals (Richter P, Chaffin J, 2004).
Cancer patients experience numerous inconveniences with their illnesses. Treatment may cause xerostomia, burning mouth sensation, vomiting, acid reflux, eating limitations and excessive sleeping. Xylitol products can help to reduce xerostomia by increasing saliva flow, which helps to neutralise the pH level and inhibit S. mutans (Rekola M, 1981; Soderling E et al, 1991; Soderling E et al, 1987).
Tooth decay, debris-covered dentures or poor oral hygiene may contribute to increased levels of plaque in older patients, causing oral infections like candidiasis. A 12-month study in the UK of 111 frail but healthy people aged 60 and over were divided into three groups with:
1. No gum
2. Chewing xylitol gum
3. Chewing xylitol gum with an antimicrobial.
The two groups given gum chewed two pieces twice a day for 15 minutes (Simons D et al, 2002).
Researchers found that the groups chewing xylitol gum lowered their risk for developing candidiasis and angular cheilitis (Simons D et al, 2002).
Adverse effects
Xylitol has no known toxicity, carcinogenicity or permanent side effects. One adverse effect may be several days of osmotic diarrhoea (if more than 100g per day is consumed by adults or 45g per day in children) or gastrointestinal symptoms such as wind, bloating or cramping, an effect similar to eating high-fibre foods. Symptoms gradually subside after several days with reduced intake of polyol foods. Polyols may then be gradually added back into the diet (Gutkowski S, 2005; Phipps K, Bruerd B, 2004).
A congenital enzyme defect known as pentosuria, which is almost wholly restricted to Jewish people of north European descent, means sufferers are unable to digest xylitol. Xylitol is absorbed into the body and the urine, causing a positive sugar test for diabetes, misdiagnosing a disease when none exists (Wang YM, Van Eys J, 1970).
Finally, individuals with temporomandibular joint (TMJ) disorder may need to refrain from chewing gum. Instead, sweets, mints or other products containing xylitol should be consumed (Phipps K, Bruerd B, 2004).
Product availability
Xylitol is available in a variety of products such as sweets, mints, toothpastes, mouthwashes, mouth sprays, nose sprays, baby mouth wipes and more.
Always read the ingredient label. In order to reap the most benefit, xylitol should be one of the first three ingredients, preferably first when selecting a gum or other products for their dental benefits.
References
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Gutkowski S (2005) X marks the spot. Contemporary oral hygiene 5(5): 10-13
Hayes C (2001) The effect of non-cariogenic sweeteners on the prevention of dental caries: a review of the evidence. J Dent Educ 65: 1106-1109
Hujoel PP, Makinen KK, Bennett CA et al (1999) The optimum time to initiate habitual xylitol gum chewing for obtaining long-term caries prevention. J Dent Res 78: 797-803
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Makinen KK, Hujoel PP, Bennett CA et al (1998) A descriptive report of the effects of a 16-month xylitol chewing gum programme subsequent to a 40-month sucrose gum programme. Caries Res 32: 107-112
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Simons D, Brailsford SR, Kidd EA, Beighton D (2002) The effect of medicated chewing gums on oral health in frail older people: a one-year clinical trial. J Am Geriatr Soc 50: 1348-1353
Soderling E, Alaraisanen L, Scheinin A, Makinen KK (1987) Effect of xylitol and sorbitol on polysaccharide production by and adhesive properties of Streptococcus mutans. Caries Res 21: 109-116
Soderling E, Isokangas P, Tenovuo J, Mustakallio S, Makinen KK (1991) Long-term xylitol consumption and mutans streptococci in plaque and saliva. Caries Res 25: 153-157
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Wang YM, Van Eys J (1970) The enzymatic defect in essential pentosuria. N Engl J Med 282(16): 892-896
This article is reproduced with permission from Dimensions of Dental Hygiene. October 2006; 4(10): 34-37
