Tooth decay, also commonly referred to as dental caries, is the result of acidic conditions in the mouth, due to bacterial activity. These conditions lead to the outer layers of the teeth slowly being dissolved, which can eventually lead to holes in the teeth (cavities) in serious cases. To combat this, xylitol gum has been suggested as a potential preventative measure – but is this backed up by scientific research?
Tooth decay affects a larger number of children in the US than any other chronic disease. Worldwide, it affects an estimated 5 billion people, and caries preventative programs are lacking in developing countries; the World Health Organisation estimates that more than 90% of cases of dental caries in developing countries are left untreated. I made this graphic for Sweet Bites, a team of 5 University of Pennsylvania students, who are entering this year’s Hult Prize with an idea they hope will combat dental caries in the slums of India.
Sweet Bites’ idea is a public health campaign using 100% xylitol chewing gum to combat tooth decay. Obviously, before agreeing to help them out with creating a graphic to help their campaign, I wanted to look into the science behind the use of xylitol to combat tooth decay. Although xylitol was discovered by French and German chemists back in 1890, research into its benefits in preventing tooth decay didn’t really commence until Finnish chemists started investigating it in the early 1970s, and since a large number of papers have been published regarding its effects with respect to tooth decay.
Xylitol is a polyol, a carbon-based compound with multiple hydroxyl groups. It’s found in low concentrations in a wide range of fruits and vegetables; industrially, it’s produced from a compound called xylan which is extracted from either hardwoods or corncobs. Xylan can be hydrolysed, and subsequently hydrogenated, to produce xylitol. Xylitol is widely used as a sugar substitute, as it’s as sweet as sugar, but contains 33% fewer calories. It’s commonly used as a sweetener in chewing gums in place of sugar – and its use could also have other benefits.
A number of field studies on the use of xylitol gum versus other types of gum show that it can have caries preventative properties. One study, published in 1995, carried out a 40 month study in approximately 1700 schoolchildren in Belize, and found that, compared to other types of gum, xylitol-containing gum reduced the incidences of tooth decay. A 2006 review by the American Dental Association also came to the conclusion that ‘the evidence is strong enough to support regular use of xylitol-sweetened gum as a way to prevent caries’, and a further review in 2011 reinforced this recommendation.
As it turns out, both the xylitol and the gum itself are important contributors to a caries preventing effect. Unlike sugar, xylitol can’t be broken down by bacteria in the mouth to produce energy; it can therefore prevent their growth and reproduction. The act of chewing gum itself can also combat tooth decay, as it leads to the production of saliva; this, along with the physical act of chewing, can help remove food debris from the mouth which could otherwise be fermented by bacteria. Additionally, it’s been suggested that xylitol can slightly increase the alkalinity of saliva, which boosts its ability to neutralise the acids produced by bacteria that can otherwise lead to decay.
In the interest of balance, it’s worth pointing out that a 2010 review of xylitol suggested that a greater number of randomised, controlled trials are needed in order to clarify the magnitude of the effect that xylitol has in preventing tooth decay. A trial using xylitol lozenges in ~700 adults in 2013 observed an 11% reduction in tooth decay, but this reduction was not deemed clinically significant. However, the authors of that study also note that their trial was carried out in areas where subjects had access to fluoridated water supplies, which can also help prevent tooth decay, and also may not be relevant to xylitol’s effect in younger populations.
What isn’t in doubt is xylitol’s effect on bacteria: a randomised controlled trial examining bacterial response to xylitol gum established that bacterial levels were ten times lower after six months of chewing gum containing 6-10 grams of xylitol. On this basis, the authors suggested that 5-6g of xylitol per day in the form of gum would be effective, and this is the amount that the Sweet Bites team are promoting. They plan to crowd-fund to raise the money to sustain their project, though if they do go on to win the Hult Prize’s £1,000,000 prize fund then they’re likely to be set to achieve their goal of reducing tooth decay rates in India even quicker.
You can read more about the Sweet Bites project over on their website, www.sweetbitesgum.com.
References & Further Reading
- Xylitol-sweetened gum in caries control – B Burt
- Controversies around Xylitol – E Söderling
- Xylitol chewing gum and caries – 40 month cohort study – K K Mäkinen