Is Sugar the Only Cause of Tooth Decay?

Not so fast: Lots of people who indulge in sugary treats don’t have cavities.

There are probably hundreds of diseases most people know little about. But there’s one that everyone on the planet can understand: tooth decay. Yes, it’s a disease. The formal name of cavities is caries, a term used only in oral health. Chances are, you’ve had many; the older you are the more you’ve had because you did not receive the full benefits of fluoride.

Now, a report says that sugars are the only cause of tooth decay, a plausible argument with which most people probably agree. But it’s not as simple as sugar intake equals tooth decay.

The finding is based on researchers looking at public health records worldwide, leading them to conclude that tooth decay – especially in the U.S. – from sugar is far too high. About 60 percent to 90 percent of school-age children and 92 percent of adults in the U.S. have or have had tooth decay, the report says.

“Only two percent of people at all ages living in Nigeria had tooth decay when their diet contained almost no sugar, around two grams per day. This is in stark contrast to the USA, where 92 percent of adults have experienced tooth decay,” said study author Aubrey Sheiham, emeritus professor of dental public health at the University College London in the UK. He adds that the sugar effect was also pronounced in Japan.

There’s no question that high sugar intake is bad for general health and that sugar can be bad for teeth. Studies have found that high sugar ingestion may increase the risk of heart disease, diabetes, and cancer.  

As a carbohydrate, it is a feast for the mouth’s bacteria, which are natural residents that fuel themselves on a variety of foods we eat that contain sugars or starches. They produce acid as a byproduct. That acid can dissolve tooth enamel if you don’t follow daily oral hygiene. The bacteria live communally, and communicate with one another, in a sticky film called plaque. That term is being replaced by the term “biofilm,” which more accurately reflects its complexity and true role in oral disease.

But something that confounds the study’s findings is that there are people everywhere who indulge in sugary treats and have little to no tooth decay. Why? Because the process is multifactorial and some people are genetically predisposed to cavities and gum disease, says caries researcher Stephen J Moss, DDS, MS, professor emeritus at New York University.

“The causes of tooth lesions (caries) are not all the same and cannot be squeezed into the same study to prove the myth that more sugars mean more cavities,” he says.

“Smooth surface lesions have different (causes) than do occlusal lesions (in the pits and fissures of the biting surface of the molars). You have to take salivary flow and fluoride, and how they work together, into account for any study and you need to understand why caries form only on particular and predictable tooth surfaces.

“It’s actually the bacteria that cause caries, and only when the microorganisms continue to produce enough acid that cannot be naturally buffered by saliva. The frequency (of ingestion) and the time at which it occurs is more important than what kind of sugar or how much sugar is present.

“How long the sugar remains in the mouth is the important factor. Whether or not your mouth is storing the fluoride ion in a reservoir that immediately reacts to the presence of acid is also very important. Picking on sugar is old-fashioned.”

A researcher who published a paper exploring “dental myths” agrees that the total amount of sugar you consume is far less important than the pattern in which you consume it.

“The things that are going to increase the risk of decay would not be the total amount of sugar at all, but what your feeding pattern is like,” Carole Palmer, DDS, told the New York Times.

Okay, so there’s a debate, but Sheiham is steadfast. “Tooth decay is a serious problem worldwide and reducing sugar intake makes a huge difference,” he insists. “The recommendation that sugar intake should be less than 10% of energy intake is no longer acceptable.”

One distinguished British dental researcher, Monty Duggal, who specializes in research on which foods damage teeth, told the Guardian that in any case, sugar’s effect on teeth is very limited because of fluoride toothpaste.

Another source on the topic says that “regarding dental caries, combinations of sugar amount/frequency (of ingestion), fluoride exposure, and food adhesiveness were more reliable predictors of caries risk than the amount of sugar alone.”

Here’s something else to consider. Your teeth, 24 hours a day, go through a natural process of losing and reabsorbing minerals. This process is controlled by saliva and the minerals it naturally contains. Cavities begin when the process is tipped in favor or mineral loss when saliva cannot overcome frequent acid attacks, sometimes from bacterial overgrowth at certain sites.

So, is Sheiham wrong? Look at it this way: it would be imprudent to ignore the clear role sugars and starches play in cavity development. On the other hand, plenty of researchers agree that more sugar does not equal more tooth decay. The process is more complicated than that. Again, in any case, proper oral hygiene and the frequency with which you eat foods that feed bacteria can overcome the threat that sugar poses.