Sulfites Inhibit The Growth Of Beneficial Gut Bacteria

A new study published by students and researchers at the University of Hawai‘i Maui College, found that sulfites in common food preservatives killed or inhibited the growth of the good bacteria found in the human gut.

University of Hawai‘i Maui College students Emily Graham, Ashley Malek and Adriel Robidoux, chemistry lecturer Dr. Peter Fisher, and microbiology and genetics professor and lead researcher Dr. Sally V. Irwin were involved in the study.

The study focused on beneficial or “good” bacteria naturally found in the human microbiome.  These bacteria are also found in fermented products rich in probiotics, such as yogurt, kimchee and kombucha. Numerous studies have indicated their benefits to immune response, diet quality, metabolic profiles, and overall health.

The research found that sulfites in food preservatives killed or inhibited the growth of the good bacteria when tested at levels generally regarded as safe by the FDA.

Dr. Irwin, who is also an adjunct professor in the Cell and Molecular Biology department at UH Manoa John A. Burns School of Medicine, said increasing evidence shows a direct correlation between diseases and alterations in the human gut and mouth microbiomes. Food preservatives may be partly to blame.

“As a geneticist and a professor of microbiology, I have been interested in the human genome and microbes, and their combined influence on human disease and health,” Dr. Irwin said. “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.

“In trying to understand what in our environment may be causing this change, the use of many food preservatives and their effects on beneficial bacteria came to mind.”

Irwin said overuse and misuse of antibiotics has been indicated as having a significant impact on our microbiome, but this is the first time food preservatives have been tested for their effects on beneficial bacteria.

The students were exposed to lab work and overcoming the common obstacles of research, such as learning how to ask questions and when to question the answers. “This is the best education I can give to future scientists,” Dr. Irwin said. “It has been exciting and incredibly satisfying for me and the students to present a significant piece of research that others in the scientific community can build upon.”

Dr. Irwin’s team intends to continue to study the effects of sulfites and other food preservatives in the lab and in living organisms, such as mice. “We have started some preliminary work looking at the effects of sulfites on enzymes found in human saliva and commensal mouth bacteria,” she said. “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.”

Dr. Irwin began preliminary work on this research topic at the Buck Institute for Research on Aging in Novato, California during a 2014 sabbatical. Her research at UH Maui College was supported by funds from the Hawai‘i IDeA Network of Biomedical Research Excellence (INBRE) grant, which is funded by the National Institute of General Medical Sciences at the National Institutes of Health. INBRE stimulates high-quality scientific research at undergraduate academic institutions statewide, including public and private colleges and nearly all of Hawai‘i’s community colleges.

“The grant allows students to get involved in biomedical research right from the beginning of their college experience, and promotes the expansion of the research science workforce,” said Dr. Robert Nichols, principal investigator and professor at the CMB department at JABSOM.

Dr. Irwin’s team published Sulfites inhibit the growth of four species of beneficial gut bacteria at concentrations regarded as safe for food in PLOS One, a multidisciplinary open access journal available online.

A public presentation of “The Human Microbiome in Disease and Health”, covering their research and an overview of work done by other researchers on the human microbiome, is scheduled on Wednesday, Nov. 29 at 5:30 p.m. in ‘Ike Le‘a Building, Room 144, at UH Maui College. The public is invited.

This is the first published research for Dr. Irwin and her team at UH Maui College. She said less than one percent of undergraduates nationwide are published in peer review journals. The new science facilities at UH Maui College were instrumental in achieving this milestone.