The widespread use of sugar substitutes has raised questions about their impact on dental health. Sugar alcohols, also known as polyols, are common alternatives to traditional sugar, offering sweetness with fewer calories. The key question is whether these compounds contribute to tooth decay or offer a protective benefit, which depends on how oral bacteria interact with them.
Defining Common Sugar Alcohols
Sugar alcohols are carbohydrates, chemically defined as polyols, which are organic compounds containing multiple hydroxyl groups. Despite their name, they are neither sugars nor do they contain ethanol. They function as bulk sweeteners, providing taste and texture similar to sucrose, but with a lower caloric content because the body incompletely absorbs them.
These compounds occur naturally in fruits and vegetables and are industrially produced for use in “sugar-free” processed foods. Common varieties include xylitol, erythritol, sorbitol, and maltitol. Xylitol and erythritol are noted for their dental benefits, while sorbitol and maltitol are widely used for sweetening and bulking in products like chewing gum and candies.
How Oral Bacteria Process Them
The interaction between sugar alcohols and oral bacteria determines their effect on teeth. Cavities are primarily caused by the acid produced by bacteria, particularly Streptococcus mutans, when they ferment dietary sugars. Sugar alcohols are largely non-fermentable by these microbes, which is the key to their dental advantage. Since S. mutans cannot effectively metabolize sugar alcohols, the bacteria cannot produce the lactic acid that lowers the pH in the mouth and demineralizes enamel.
Xylitol is particularly disruptive to the bacteria’s metabolism. S. mutans attempts to transport xylitol into its cell, treating it like a sugar, but cannot break it down for energy. This creates a “futile cycle” where the microbe wastes energy and is effectively starved, reducing its growth and acid output.
Erythritol also shows a strong inhibitory effect on S. mutans growth and the formation of plaque. While all sugar alcohols are considered non-cariogenic because they do not fuel acid production, the degree of anti-caries activity varies. Xylitol and erythritol are actively cariostatic, meaning they suppress cavity formation, whereas others like sorbitol are passive, simply not contributing to the decay process.
Effects on Cavity Prevention
The inability of S. mutans to ferment sugar alcohols translates into measurable benefits for cavity prevention. Since acid production is minimized, the mouth’s pH remains neutral, preventing enamel demineralization. This allows the natural process of remineralization, where calcium and phosphate ions are redeposited onto the tooth surface, to occur more effectively.
Consuming products containing sugar alcohols, especially xylitol, reduces the overall mass of dental plaque and decreases the bacteria’s ability to adhere to the tooth surface. This reduction in the S. mutans population lowers the risk of developing new cavities. Xylitol consumption, often in doses of about five grams spread throughout the day, has been associated with a significant reduction in caries incidence.
Erythritol is also highly effective, with some research suggesting its efficacy in caries prevention is comparable to xylitol. These beneficial polyols are widely incorporated into dental products like sugar-free chewing gum, mints, and toothpaste. The stimulation of saliva through chewing gum further aids in cavity prevention by buffering plaque acids and facilitating bacterial clearance.