Starch might impact your oral health—depending on your DNA

New research reveals that your genetic makeup influences how starch shapes your oral microbiome—potentially affecting your risk for cavities and gum disease.

Study: The Impact of Human Salivary Amylase Gene Copy Number and Starch on Oral Biofilms. Image Credit: Stastny_Pavel / Shutterstock

It's common knowledge that sugar causes cavities, but new Cornell University research explores how genetic variation in AMY1, a gene involved in starch digestion, influences the composition of oral bacteria, which may have implications for dental health.

The study, published in the journal Microorganisms, explores the oral microbiome's response to starch. It finds 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 and assistant professor of molecular nutrition. "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. 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 linked to periodontitis. This study further examines how starch influences bacterial composition in the mouth, particularly affecting Veillonella and Atopobium.

However, it was unclear how the salivary amylase enzyme interacts with its main substrate, starch, to alter the oral microbiome and increase disease risk.

"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 Veillonella and Atopobium responded differently depending on both AMY1 copy number and starch presence, suggesting that certain bacteria may be more influenced by genetic variation in starch digestion."

The researchers also found evidence that the oral microbiome has co-evolved in response to increasing copies of AMY1, which is found in higher numbers in populations where there's a long history of agriculture and starch consumption. In the pool of 31 samples taken in Ithaca, N.Y., the AMY1 number ranged from two to 20 copies.

"The populations that historically had greater access to starch tend to have more copies," Poole said, "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 an in vitro study using cultured oral biofilms, the researchers saw increased populations of bacteria, like Streptococcus, in starch-supplemented biofilms, particularly in individuals with a high AMY1 copy number. However, Veillonella and Atopobium showed the strongest changes in response to starch and AMY1 copy number, suggesting a more complex relationship between these bacteria and starch metabolism.

"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. "Our results suggest that different bacterial species behave differently depending on available carbohydrates and an individual's genetic makeup. It's pretty incredible – how we adapt and these microbes turn around and adapt, too."

The study also found that biofilms from individuals with periodontitis had lower bacterial diversity compared to those from healthy individuals, which may have implications for how starch metabolism influences oral disease risk over time. Additionally, starch supplementation reduced microbial diversity in biofilms, possibly by favoring certain bacteria over others.

The Schwartz Research Fund and the National Institutes of Health provided funding.