It’s common knowledge that sugar causes cavities, but new Cornell University research provides evidence that starches could also. The study, published in Microorganisms, explores the response of the oral microbiome to starch, finding that the number of copies of a particular gene, AMY1, in combination with starch, alters the complex composition of bacteria that play a role in oral health.

“Most people have been warned that if you eat a bunch of sugar, make sure you brush your teeth,” said Angela Poole, senior author: “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”.

AMY1 codes for the salivary amylase enzyme, which helps break down starch in the mouth.

Poole, in prior studies, found that a high AMY1 copy number is associated with higher levels of the species Porphyromonas endodontalis, which is strongly associated with periodontitis and gum disease.

In the pool of 31 samples the AMY1 number ranged from two to 20 copies: “The populations that historically had greater access to starch tend to have more copies, which 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”.

In saliva samples with a high AMY1 copy number, the researchers saw increased populations of bacteria, like Streptococcus, that feed off the starch’s sugars: “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. 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”.

From: https://www.sciencedaily.com/releases/2025/02/250226163246.htm