Dental Warning As New Cavity-Causing Food Type Revealed

Eating starch can lead to cavities—just like sugar does—among people with too many copies of a certain gene.

This is the conclusion of researchers from Cornell University in New York who studied how the microbial communities in the mouth react to AMY1, which codes for an enzyme, amylase, that helps the saliva to break down starch.

Starch-rich foods include beans, pasta, potatoes and rice.

“Most people have been warned that if you eat a bunch of sugar, make sure you brush your teeth,” said paper author and molecular nutrition professor Angela Poole in a statement.

“The takeaway finding here is that, depending on your AMY1 copy number, you may want to be just as vigilant about brushing your teeth after eating those digestible starches.”

According to the researchers, higher AMY1 copy numbers has previously been associated with both a greater risk of cavities and periodontal disease, as well as higher oral levels of the bacterium Porphyromonas endodontalis, which can cause root canal infections.

However, the exact mechanism by which salivary amylase interacts with starch to change the oral microbiome and increase the risk of disease has not been clear.

“That’s what we wanted to know in this experiment. What’s going on in the mouth if someone eats starch, and is the answer different if their copy number is high or it’s low?” said Poole.

“What we found was that there are other bacteria involved in these processes and that the changes depended on AMY1.”

In the study, the team collected saliva samples from 31 donors in Ithaca, New York, who had AMY1 numbers ranging from between two and 20 copies of the gene.

The team found that saliva samples taken from people with a high AMY1 copy number contained more bacteria such as Streptococcus that feed off the sugar in starch.

“If someone has a high copy number, they break down starch efficiently—and bacteria that like those sugars are going to grow more in that person’s mouth,” said Poole.

Other bacteria—such as Atopobium and Veillonella—were found, meanwhile, to be less abundant in people with a higher AMY1 copy number.

“So you can have species behave differently based on the different substrates. It’s pretty incredible how we adapt and these microbes turn around and adapt, too,” said Poole.

Alongside finding that the oral microbiome has coevolved in response to increasing copies of AMY1, the team also reports that the gene tends to be more common among populations with a long history of agriculture.

“The populations that historically had greater access to starch tend to have more copies,” Poole said.

This, she added, “makes sense from a practical standpoint, because it would have given you a survival advantage when food is scarce, to be able to break down those starches more efficiently.”

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about tooth decay? Let us know via science@newsweek.com.

Reference

Superdock, D. K., Johnson, L. M., Ren, J., Khan, A., Eno, M., Man, S., & Poole, A. C. (2025). The Impact of Human Salivary Amylase Gene Copy Number and Starch on Oral Biofilms. Microorganisms, 13(2). https://doi.org/10.3390/microorganisms13020461