UH-Maui College research reveals impact of food additives

Food preservatives might throw off the balance of “good” bacteria in the human gut, which could have implications for health, according to a new study by faculty and students at University of Hawaii Maui College.

Led by professor Sally V. Irwin, a geneticist and microbiologist, the researchers found that sulfites killed or stopped the growth of beneficial bacteria in the lab when applied in amounts considered safe by the federal government.

Overuse of antibiotics has been shown to have similar effects, but the study published in the online journal PLOS One is the first to examine the impact of food preservatives on beneficial bacteria, said Irwin, who is also an adjunct professor at UH Manoa’s medical school.

“I thought it was really significant,” Irwin said in an interview Monday. “Like antibiotics, when preservatives first came into our food in the early 1960s, everybody was thinking about getting rid of the pathogens. We weren’t thinking about the effects on good bacteria.”

Both antibiotics and food preservatives have had a huge impact in preventing illness and keeping food edible. But they might also play a role in altering the human “microbiome,” the community of microorganisms living in or on the body that is a key to health.

“Studies show a significant increase over the past 40 years in food allergies, obesity and metabolic disorders that have a direct correlation to disbiosis, or changes in the microbiome,” Irwin said.

“There is a lot of work on how antibiotics can change our microbiomes, especially with kids who are developing their immune system,” she said. “A lot of people are being exposed to food preservatives on a daily basis. It may not be as significant an impact, but you have continual impact.”

The study, published Oct. 18, is titled “Sulfites inhibit the growth of four species of beneficial gut bacteria at concentrations regarded as safe for food.” Along with Irwin, the authors were UH Maui chemistry lecturer Peter Fisher and students Emily Graham, Ashley Malek and Adriel Robidoux.

Sulfites occur naturally in some foods and are also added as a preservative. They are found in wine and in some dried fruits, juices, processed fish and meats, and canned goods such as coconut milk.

They are listed on the ingredient label above a certain threshold. Because some people are allergic to sulfites, the Food and Drug Administration has banned using them to maintain the color and crispness of fresh produce, such as in salad bars.

The Maui research group applied sodium sulfite and sodium bisulfite to beneficial bacteria that are common in the human gut and also found in fermented products such as yogurt and kim chee. The sulfites killed all three Lactobacillus species within about four hours and stopped the growth of the Streptococcus that was tested, Irwin said.

Graham, one of the student researchers, said the results open up a new field for research.

“I think it’s a widely applicable project to people’s everyday lives because it’s regarding food additives and products that we consume all the time,” she said. “These findings have shown that sulfite preservatives are affecting our microbiome.”

“The microbiome can affect things such as vitamin production, neurotransmitters and the nervous system,” she said. “Even though they (bacteria) live in our digestive system, they have effects throughout the whole body.”

Robidoux, a fellow student on the project, said he never anticipated doing such cutting-edge research when he applied to UH Maui College.

“It was in an intro to genetics class that I took with Dr. Irwin that my brain just opened up and I knew that’s definitely what I’m interested in,” he said.

The project was supported by a grant from the Hawaii IDeA Network of Biomedical Research Excellence, which is funded by the National Institutes of Health and aims to spur scientific research at the undergraduate level.

Robidoux, 31, and Graham, 28, are headed to UH Manoa after receiving their associate degrees next semester. Irwin plans to continue the research at Maui College.

“We would like to collaborate with another lab to do some mouse studies or use an artificial gut environment to look at effects on a mixture of bacteria,” she said.