The Wonder of Xylitol

What is Xylitol?

Xylitol is a naturally occurring substance found in fruits like plums; berries, such as raspberries and strawberries; vegetables, as in lettuce and corncobs; and hard woods, such as birch and beech trees. Additionally, it’s produced in our own bodies during the normal metabolism of glucose. A five-carbon sugar alcohol or polyol, it is as sweet as sucrose but is noncariogenic. Xylitol is nutritive because it contains calories, unlike artificial sweeteners, eg, saccharin. (See Table 1).

Xylitol is a white crystalline substance that looks very similar to sugar. It can be purchased in bulk form and used as a sugar replacement at an approximate 1-to-1 ratio. However, Xylitol, like the other polyols sorbitol and mannitol, produces a cooling sensation in the mouth, which is why it is often associated with a mint flavor.

How does Xylitol work in caries prevention?

Xylitol is noncariogenic because it does not ferment (produce acids in the oral cavity). As a five-carbon sugar alcohol, Xylitol cannot be digested by bacteria, as opposed to natural sugars or other sugar alcohols that are six-carbon molecules and fermentable. Other sugar alcohols ferment very slowly and, therefore, are considered noncariogenic.

The thinking behind Xylitol’s inability to ferment is that Xylitol interferes with the metabolism of Streptococcus mutans when it is transported into the cell, where it probably stays bound to the transport protein. This bond is unbreakable by the usual enzymes so the transport protein is essentially tied up. The transport protein can’t go back out to get more glucose to provide the cell with energy. The reduced number of functioning transport proteins is the process thought to reduce acid production in S. mutans.¹

An additional hypothesis about Xylitol’s mechanism of action is that it helps reduce the number of S. mutans in plaque and, ultimately, in the oral cavity. The theory is that the bacteria are not as able to produce the sticky extracellular polysaccharides that bind bacteria together and, as a result, they can’t adhere as readily to the tooth surface.¹

Does Xylitol have other health benefits besides its anti-cariogenic effect?

Xylitol has 40% fewer calories than sucrose and is often used as a sugar substitute in diabetic diets because of its decreased caloric value. Sucrose has 4 calories per gram and Xylitol has about 2.4 calories per gram (Table 1, page 18). Xylitol is digested slowly, slowing the rise of blood glucose levels. Xylitol has a glycemic index of seven versus glucose, which is 100. Xylitol has 75% fewer carbohydrates than sucrose because only about a quarter of the Xylitol consumed is converted into glucose.

Xylitol has been shown to help reduce middle ear infections.² The main culprit in the middle ear infection is a bacterial relative of S. mutans. Probably the same logic about bacterial adherence applies to middle ear infections, however, more research is necessary.

In order to gain the benefits of Xylitol, it must be ingested frequently, correct?

Yes, we recently completed a study to establish the minimal effective dose of Xylitol needed per day, delivered via chewing gum, to reduce S. mutans. No effects were found with 3 g per day but noticeable changes did occur at 6 g and 10 g per day. There was a statistically significant reduction of S. mutans in plaque and saliva over 6 months in the groups with these higher levels of Xylitol per day.³ We have also looked at the effect of the frequency of Xylitol gum use per day, holding the dose constant at the level of 10 g per day. It appears that the effect increases with frequency of intake (these results have not yet been published). For caries prevention, I would recommend 6 g to 10 g of Xylitol per day via chewing gum, as we know this is an effective delivery vehicle. To achieve the maximum effect, break that dose up into three or four administrations per day. Xylitol gum needs to be chewed for 5 minutes to get all of the Xylitol out of the gum and into the mouth.

References

1. Makinen KK. Can the pentitol-hexitol theory explain the clinical observations made with xylitol? Med Hypotheses. 2000;54:603-613.
2. Uhari M, Tapiainen T, Kontiokari T. Xylitol in preventing acute otitis media. Vaccine. 2001;19(suppl): S144-147.
3. Milgrom P, Roberts,MC, Ly K, Rothen M, Mueller G. Streptococcus mutans response to increasing amounts of xylitol delivered in chewing gum. J Dent Res. In press.

From Dimensions of Dental Hygiene. October 2005;3(10):18, 20.