Xylitol's effect on cariogenic bacteria.

- Although it is a form of sugar, xylitol is not a suitable food source for the types of bacteria that cause cavities. As a result, when it's present in a person's mouth, their population tends to suffer.


A) Xylitol's starvation effect.


Cariogenic (decay-causing) bacteria have trouble metabolizing (feeding on) xylitol.


When xylitol (a five-carbon sugar-alcohol) is available to cariogenic bacteria, they transport it through their cellular wall via an intake system that's intended for fructose (a five-carbon sugar).

As this process takes place, the xylitol molecule gets transformed into xylitol phosphate, a compound that the bacteria cannot metabolize (break down and digest).

The bacteria starve.

Over time as the level of unmetabolized xylitol phosphate builds up within the bacteria it becomes toxic for them. (It interferes with the metabolic pathways that they rely on for nourishment.)

That means, a regular supply of xylitol in a person's mouth creates a situation where at minimum cavity-forming bacteria are malnourished or starved. At the extreme, some will die off. And as a result, colonies of these types of cavity-causing bacteria will be impaired, thus inhibiting their ability form tooth decay.

Why this is beneficial.

A decrease in the number of cariogenic bacteria in dental plaque will correlate with a decrease in the level of acidic byproducts formed by their digestion of sugars. As a result, the overall acidity of the plaque will be less, thus helping to maintain an environment where tooth decay is less likely to occur.

Our page How cavities form may help you understand the information on this page better.)

B) Xylitol-induced population changes.

The presence of xylitol in a person's mouth favors the growth of less virulent strains of cariogenic bacteria.


A person's long-term exposure to xylitol will tend to affect the population size of various types of cariogenic bacteria that live in their mouth.


Within the population of cavity-causing bacteria living in dental plaque, some will have a (genetically) altered fructose uptake system (one that can't transport xylitol). Because of this, these bacteria will not accumulate toxic levels of xylitol phosphate.

The population shift.

This means that these xylitol-resistant bacteria will continue to thrive whereas their xylitol-sensitive counterparts will not. Over time, the numbers of sensitive bacteria will decrease and the numbers of resistant ones will grow and ultimately predominate.

How this is beneficial.

Research suggests that xylitol-resistant strains of cariogenic bacteria are less virulent (less capable of cauing tooth decay) than their counterparts.


One theory suggests that xylitol-resistant bacteria have impaired adhesive properties.

The ability of bacteria to cause decay depends, in part, on their ability to adhere to a tooth's surface. Since xylitol-resistant strains have difficulty in this regard, their ability to create the conditions needed for tooth demineralization is reduced.


Input from site visitors.


Perhaps it would be wise to use Xylitol intermittently, and short term, since science is reporting the emergence of numerous xylitol resistant mutans streptococcus. .. and did I read it correctly, with cancer causing capacity ?

Thanks for posting.

Your questions simply point out the need for an authoritative body (ADA, FDA, WHO etc..) to establish formal guidelines and recommendations.

We'd be interested in reading your reference sources. You can post URL's in our comments section if you'll just use the term "(dot)" instead of an actual ".".

We double checked the FDA.gov website and did not see a statement there regarding cancer concerns. Nor did our search of the Pub Med database. What mentions we did find on the web in general made reference to xyltiol quantities substantially higher than those discussed on our website.

In regard to bacterial resistance, this fairly recent publication (2012) suggests that even xylitol-resistant S. mutans (a type of bacteria that causes cavities) have an anti-cariogenic (cavity prevention) effect.


Do you have any references for Xylitol not being metabolised by bacteria?


Here's a link to our references page.
Probably most of these studies make some mention to the issue.

Pretty much at random, we clicked the link for the paper titled "Sugar substitutes, chewing gum and dental caries--a review."
In its abstract is the sentence: "Because it is not fermented by oral bacteria, xylitol is considered to be non-cariogenic ..."

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