Sugar-Free Doesn’t Mean Worry-Free

Sugar-free products may harm teeth, says SDM researcher Sok-Ja Janket (right), with study coauthor Mohamad Nadimi (GRS’09, SDM’13). Photo by Kalman Zabarsky

The ubiquitous term “sugar-free” may trigger a false sense of security, says Sok-Ja Janket. She has long suspected that diet sodas and sugar-free candy, chewing gum, and other products, although preferable to sugar-sweetened products when it comes to preventing cavities, can also take a toll on dental health.

As lead researcher in a review study recently published in the British Dental Journal, the Goldman School of Dental Medicine research associate professor reports a link between widely used sugar substitutes and dental erosion, a gradual loss of the teeth’s hard coating. The study grew out of a thesis by third-year dental student Mohamad “Hadi” Nadimi (GRS’09, SDM’13)

According to Janket, sugar-free drinks and candies with acidic additives, most common in fruit-flavored products, pose a high risk for dental erosion. (Dental erosion differs from tooth decay, which is caused by bacteria.) In a comprehensive search of the dental literature, Janket and her coresearchers found a link between dental erosion and the use of sugar-free products with the acidic additives sorbitol and xylitol, and the findings indicate that the longer these acids stay on the teeth—in slow-melting candies, for example—the greater the risk of harm.

BU Today asked Janket about the implications of her findings, what kind of damage sugar-free products might be doing to our teeth, and whether some products are worse than others.

BU Today: What led you to suspect that sugar-free products might not be as beneficial to dental health as is widely assumed?

Janket: When several patients reported tooth sensitivity from unknown origin, we carefully evaluated their dental history and concluded that it might be related to sugar-free confections with acidulants, or acidic additives. It is not sugar-free polyols that cause problems, but the acids that are added.

Did the findings surprise you?

Not really. It just takes curious researchers with ability to search for the information that is necessary. We needed to find out the pH level where dental hard tissues lose minerals. The lower the pH, the higher the acidity. This information has existed, scattered throughout various research studies, since the 1970s. We found it and connected the dots.

Are dentists seeing more erosion than previously?

We knew that sugar-free products prevent cavities and also knew that the addition of acids could not be healthy. More dental erosion may have been noticed, but no one attributed this increase to acidic additives in sugar-free products.

Can you explain dental erosion in lay terms?

We have to start with dental caries first. Dental caries occur when microorganisms residing in the mouth, which are called “normal flora” and live in harmony under normal conditions, ferment carbohydrates and generate acids. These acids then leach out calcium from the tooth structure and dental caries begin.

Dental erosion is when acids from foods or industrial sources (some jobs that use acids, etc.) leach out calcium. Thus, dental erosion is a process of mineral loss by chemical action, without involving microorganisms.

Do you see the paradox here? We use sugar-free products to avoid acids made by the microorganisms, to prevent dental caries, but we add them in sugar-free products.

The potentially harmful acids are found in almost all sour-tasting products, including Sprite, 7UP, Gatorade, Mountain Dew, and Crystal Light, as well as in orange juice.

Your article refers to the public’s false sense of security. Would you advise people to avoid or cut back on artificially sweetened products?

Few would think of going to bed after drinking orange juice without brushing their teeth. With sugar-free products, however, people may think it is safe to do so. This is the false security we mentioned in our paper.

Sugar-free products (polyols) have proven dental benefits. However, like everything else, they should be used in moderation. The public should be aware of the potential problems from acidic additives as well as the gastrointestinal consequences. I use sugar-free products, but restrict them to those products without acidulants, which are listed in the ingredients.

Who is most vulnerable to dental erosion?

Acidulated sugar-free products with long exposure, such as sour-tasting lollipops, will cause the most harm. I would say children might be the most vulnerable.

Why do you think the effect of sugar-free products on dental health hasn’t been closely studied?

What we reported is not rocket science. However, this kind of research requires critical thinking and the ability to view science in a broader context. We were able to connect the dots that were scattered all over research from the past four decades.

Do you think most dentists assume these products are a healthy alternative to ones sweetened with sugar?

After our publication, they may be more aware of the hidden danger.

Do some sugar-free products have no acidic additives, and are they safer in terms of dental health?

Some sugar-free confections appear to be safe. They are nonacidic flavors such as peppermint, spearmint, butterscotch, or mint-chocolate chip. It helps to control my physiologic, not diabetes-related, hypoglycemia (low blood sugar) during long distance-driving.

What products are likely to do the most damage?

Most sour-tasting products contain acids. Consumers should check ingredients. If the product contains ascorbic, adipic, glutaric, or tartaric acid, it will cause pH levels to fall to a point where dental erosion can occur.

You mention that adding calcium and phosphate could stem adverse effects—is anyone studying this?

I hope someone will pick up the baton and do these studies. It would not be easy to study, but we can do simulated research.

Could using sugar-free products in moderation minimize the adverse effects? Are they overused because they’re perceived as harmless?

I believe the harmful effects would be minimized if one uses them in moderation. I believe the public perceives these products as safe but in reality, a subgroup may not be.

Will you pursue this research?

We plan to do more studies to confirm those flavors I tentatively suggested are indeed safe.