Sugar substitutes are widely used as alternatives to traditional sugar, such as sucrose, often to limit calorie intake and reduce the risk of cavities. Sugar alcohols are frequently found in sugar-free gums, candies, and baked goods. This has led to questions about their impact on dental health. Scientific research provides a clear answer regarding whether these compounds contribute to tooth decay. This article clarifies the process of cavity formation and explains how sugar alcohols interact with oral bacteria.
The Mechanism of Tooth Decay
Cavities begin when specific bacteria in the mouth metabolize certain carbohydrates. The primary culprits are acidogenic bacteria, such as Streptococcus mutans, which reside in the sticky film known as dental plaque. These bacteria consume fermentable carbohydrates, like glucose, fructose, and especially sucrose, as their main source of energy.
The metabolism of these sugars produces organic acids, most notably lactic acid, as a waste product. This acid drastically lowers the pH level in the immediate environment surrounding the tooth enamel. When the plaque pH drops below a critical threshold, typically around 5.5, the acid begins to dissolve the mineral structure of the tooth enamel, a process called demineralization.
Saliva naturally works to buffer this acid and promote remineralization, but frequent or prolonged acid attacks overcome this natural defense. If the cycle of acid production and demineralization continues over time, it leads to a net loss of tooth structure, resulting in the formation of a cavity. The risk of decay is therefore directly tied to the ability of oral bacteria to rapidly break down a substance into acid.
Sugar Alcohols Defined and Differentiated
Sugar alcohols are a class of compounds also known as polyols, which are neither sugar nor alcohol in the conventional sense. They are carbohydrates with a chemical structure that contains multiple hydroxyl groups, derived from the reduction of a sugar. These compounds occur naturally in various fruits and vegetables, and they are also produced industrially for use in foods.
The fundamental difference between sugar alcohols and fermentable sugars lies in their metabolic pathway, particularly concerning oral bacteria. The primary cavity-causing bacteria, such as S. mutans, are unable to effectively metabolize most sugar alcohols. This inability means that consuming polyols does not result in the rapid production of acid that causes the critical pH drop required for demineralization.
Because oral bacteria cannot ferment them into acids, sugar alcohols are considered non-cariogenic. This characteristic is why they are widely used in products marketed as “sugar-free.” The absence of a strong acid-producing reaction prevents the enamel from dissolving, thereby protecting the tooth surface.
The Cavity Answer: How Specific Sugar Alcohols Affect Dental Health
The general answer is that sugar alcohols do not cause cavities, but their effects on dental health vary significantly by type. Some polyols are merely neutral, while others provide an active protective benefit. This difference is important for consumers seeking the best dental substitutes.
Protective Polyols
Xylitol and erythritol are considered the most beneficial sugar alcohols for oral health, often described as cariostatic because they help suppress decay. Xylitol, a five-carbon sugar alcohol, cannot be metabolized by S. mutans and is thought to interfere with the bacteria’s energy-producing pathways. Regular use of xylitol has been shown to reduce the amount of the harmful S. mutans bacteria in plaque and saliva.
Erythritol, a four-carbon polyol, has demonstrated a particularly strong efficacy in clinical trials. Studies suggest erythritol is even more effective than xylitol at reducing dental plaque weight and inhibiting the growth and adherence of S. mutans to tooth surfaces. It suppresses bacterial growth through mechanisms that interfere with enzymatic pathways. Both erythritol and xylitol are beneficial for preventive dental care.
Neutral Polyols
Other common sugar alcohols, such as sorbitol and maltitol, are non-cariogenic but lack the active anti-bacterial effects of xylitol and erythritol. Sorbitol is metabolized much more slowly by oral bacteria than table sugar, which means it does not cause the severe pH drop associated with enamel erosion. However, some research suggests that dental plaque may adapt to sorbitol over time, potentially weakening its protective effect compared to other polyols.
Maltitol, derived from maltose, is another polyol that does not contribute to tooth decay. Like sorbitol, maltitol is broken down slowly by oral bacteria, leading to a higher plaque pH and a reduction in acid production compared to sucrose-containing products. These polyols are classified as neutral because they do not actively inhibit the growth or adhesion of cavity-causing bacteria to the extent that xylitol or erythritol do.