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Published: February 27, 2025
It’s well established that sugar contributes to cavities, but a new study suggests that starch could also play a role—depending on a person’s genetic makeup.
Published in Microorganisms on February 19, the study investigates how the oral microbiome responds to starch. Researchers found that the number of copies of a particular gene, AMY1, influences the composition of bacteria that affect oral health.
“Most people have been warned that if you eat a bunch of sugar, make sure you brush your teeth,” said Angela Poole, the study’s senior author and an assistant professor of molecular nutrition at Cornell University. “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 Role of AMY1 in Oral Health
The AMY1 gene codes for the enzyme salivary amylase, which helps break down starch in the mouth. Previous studies have linked AMY1 to cavities and periodontal disease, but its direct interaction with starch and oral bacteria remained unclear until now.
For the study, lead author Dorothy Superdock, Ph.D. ’23, and her team collected saliva samples from 31 individuals with varying AMY1 copy numbers. They then added starch to the cultured samples, or biofilms, to analyze bacterial changes. The results showed that the diversity of bacteria generally decreased when starch was introduced. Notably, samples with high AMY1 copy numbers experienced significant reductions in Atopobium and Veillonella bacteria, while Streptococcus levels increased.
All three bacterial species have been associated with cavities and gum disease.
“Some increased and some decreased, so it’s not as simple as saying, ‘The whole thing is good or bad,’” Poole explained. “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.”
Evolutionary Adaptations and Oral Health Risks
The study also suggests that the oral microbiome has evolved in response to increasing AMY1 copy numbers, which are typically higher in populations with a history of agriculture and starch consumption. The saliva samples analyzed in the study had AMY1 copy numbers ranging from two to 20.
In high-AMY1 samples, the researchers observed an increase in Streptococcus bacteria, which thrive on sugars released from starch breakdown.
“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,” Poole said. “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.”
Implications for Dental Care
While the study does not provide direct clinical recommendations, it underscores the importance of personalized dental hygiene. People with high AMY1 copy numbers may need to be as cautious about starchy foods as they are with sugary ones.
Study Contributors
The research was conducted by a team including Lynn M. Johnson, director of the Cornell Statistical Consulting Unit; doctoral student Megan Eno ’22; former lab manager Jennifer Ren ’19; and researchers Alizeh Khan ’22 and Shuai Man ’23, M.A. ’24.
Citation
Dorothy K. Superdock et al., “The Impact of Human Salivary Amylase Gene Copy Number and Starch on Oral Biofilms,” Microorganisms (2025). DOI: 10.3390/microorganisms13020461.
Disclaimer: This article summarizes scientific research and is for informational purposes only. It should not be interpreted as medical advice. Readers are encouraged to consult their dentist or healthcare provider for personalized recommendations regarding oral health.
