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UH-Maui studies effects of food preservatives on mouth microbes

Research published in peer-reviewed journal and follows study on gut bacteria

The University of Hawaii Maui College research team of (from left) Luz Maria Deardorff, Francesca Yadao, Rachael Kent, Peter Fisher, Sally Irwin, Michelle Gould and Junnie June pose for photo following the publication of their recent peer-reviewed paper. Photos courtesy of Sally Irwin

A small group of University of Hawaii Maui College students and faculty broke new ground last month by exploring the impacts of preservatives found in food on the mouth microbiome, one of the first studies of its kind and among the few peer-reviewed publications out of the program.

The published paper titled “Sulfite preservatives effects on the mouth microbiome: Changes in viability, diversity and composition of microbiota” was posted earlier this month in PLOS One, a peer-reviewed scientific journal in the Public Library of Science.

“This whole process was such a great learning experience for the students. They saw what it takes to get science published in a peer-reviewed journal,” said Sally Irwin, a professor in UH-MC’s science department. “It’s no small undertaking, but the process is so important. It’s what makes science unique because it is not only founded on data, but through peer review the data is scrutinized for accuracy and value.”

In the study, the students and faculty take a look at the impacts of processed foods, which make up about 70 percent of the North American diet, as well as the sulfites and other preservatives added to these foods mainly to limit bacterial contamination.

Though the microbiome is a collection of small microbes, like bacteria, fungi, viruses and genes, it plays a big role in human health and wellness. The mouth microbiota are the first to encounter food and therefore likely to be the most affected by what’s being eaten, according to the UH-MC study.

Luz Maria Deardorff (front) and Cole Whitney (back) pipet reagents for their experiment that involved studying the impacts of sulfite preservatives on the mouth microbiome at the UH-MC science lab.

An imbalance in the mouth microbiome can lead to oral diseases such as cavities, gum infections and oral mucosal disease, which involves the inside lining of the cheeks and lips, as well as systemic diseases within the gastrointestinal, cardiovascular and nervous systems, according to the UH-MC study, which points to recent research on oral microbiota.

Saliva was collected from 10 individuals — two males and eight females ages 18 to 60, all in overall good health — between two to 10 hours after eating or drinking something other than water. Collections took place twice a week over the course of four to five weeks, with each participant supplying eight samples in total.

“We were definitely surprised by how fast, almost immediate, within 10 minutes, exposure of the mouth microbiome to sulfites, we saw significant cell death,” Irwin said.

What makes this publication unique for UH-MC is that most small colleges focus their resources on teaching, not research, which made access to funding and equipment for extensive studies and projects challenging for the team, Irwin said.

Still, about two and a half years of work in the lab was done, such as collecting and processing large amounts of data in house, developing techniques and optimizing protocols, extensive experimentation and writing the paper, Irwin said.

“The mouth microbiome work has not been as extensively studied as the gut and so we needed to develop the techniques more on our own,” she said. “We were also more limited by cost than bigger labs so we came up with the idea to use a technique that detects bacterial cell death that had not been previously used to study the microbiome.”

Though the COVID-19 pandemic delayed their work, too, it did not stop it completely.

Irwin said that all of the students who contributed to the paper had either continued their education at UH Manoa or pursued careers in their chosen fields, but stayed with the project to help see it through to the end.

Rachael Kent, Francesca Yadao and Luz Maria Deardorff were the research students “that were instrumental to the success” of the research and publication. Peter Fisher, Michelle Gould and Junnie June — all current faculty or lecturers — were mentors and involved in the process.

Maui students under the Hawaii IDeA Networks of Biomedical Research Excellence program included Nadia Takayama, Cole Whitney, Noah Zolotow and Kyle Oshiro, who presented the research at the John A. Burns School of Medicine at UH Manoa.

This month, Deardorff presented this research again at the Hawaii-California joint chapter of the American Society for Microbiology meeting.

UH-MC previously published an article in 2017 on the effects of sulfites on beneficial gut bacteria before focusing on the mouth microbiome.

“Our 2017 paper was the first paper — that we are aware of — that asked the question ‘are food preservatives harmful to beneficial (probiotic) bacteria found in the human gut?’ “ Irwin said. “There were no other studies at that time that looked specifically at this.”

Funding for UH-MC’s most recent research on the mouth microbiome was from the National Institutes of Health through the IDeA Networks of Biomedical Research Excellence program, which promotes biomedical research opportunities for undergraduates.

Up next, the UH-MC lab plans to research the effects of several other types of food preservatives on certain enzymes found in the mouth as well as look at the effects of preservatives found in skin products on the skin microbiome.

“I think all of us are very proud of the work we did and its contribution to microbiome research,” Irwin said.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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