Oral microbiome dictates starch’s effect on cavities
Sugar's effect is well-known but starches could also be a factor.
It is well-known that sugar causes cavities, but new research provides evidence that – depending on a person’s genetic makeup – starches could also be a contributing factor.
The study, published in the journal 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, Assistant Professor in Division of Nutritional Sciences at Cornell University, said: “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.”
The takeaway finding is that you may want to be just as vigilant about brushing your teeth after eating digestible starches.
Angela Poole
The researchers collected saliva samples from 31 subjects with a range of AMY1 copy numbers – copies of the AMY1 gene in the DNA – and added starch to the cultured samples, or biofilms, to see how the bacterial makeup changed.
They found that, in general, the diversity of bacteria decreased when starch was added. For those samples with high numbers of AMY1, the starch significantly reduced the proportions of two bacteria, Atopobium and Veillonella, while Streptococcus appeared to increase. All three bacteria are associated with tooth decay or gum disease, Poole said.
“Some increased and some decreased, so it’s not so straightforward as saying, ‘The whole thing is good or bad,'” Poole said. “It’s an interaction, but it looks like the AMY1 copy number, as well as which species are present in people’s mouths when they eat starch, is affecting the risk for developing these diseases.”
Previous studies have associated AMY1 with cavities and periodontal disease. 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. But how the salivary amylase enzyme interacts with its main substrate, starch, to alter the oral microbiome and increase disease risk was unclear.
“That’s what we wanted to know in this experiment,” Poole said. “What’s going on in the mouth if someone eats starch, and is the answer different if their copy number is high or if it’s low? What we found was that there are other bacteria involved in these processes and that the changes depended on AMY1.”