A new study has shown that microplastics can alter gut microbiome, where those changes resemble patterns associated with depression and colorectal cancer.
The research, conducted within microONE, a project led by the CBmed research center in Graz, Austria, in collaboration with international partners, was presented at the United European Gastroenterology (UEG) Week 2025 on Tuesday.
“We live in a close relationship with our gut microbiome, and even subtle changes could have implications for our health,” Christian Pacher-Deutsch, lead author of the study and a Ph.D. student at the research institution CBmed GmbH and the Medical University of Graz, Austria, told Newsweek.
“While it’s too early to draw definitive conclusions, the patterns we observed in our bioreactor experiments suggest that this is something worth paying attention to,” he said.
Why It Matters
Microplastics, which are plastic particles smaller than 5 millimeters commonly found in the environment, and their impact on human health have been gaining increasing attention in recent years.
Given the prevalence of plastic use in today’s environment, Pacher-Deutsch said that “people are constantly exposed through food, water, air, and even everyday items like clothing and packaging,” and the particles have already been found in various parts of the human body, including the gut and bloodstream.
He added that research also estimates a person’s weekly intake of microplastics could be “as high as the equivalent of a credit card, though these numbers are still uncertain,” which he said highlights the importance of treating “plastic pollution as a serious public health issue.”
What The Study Found
The researchers used stool samples from five healthy volunteers to grow gut microbiome cultures in their lab, and then exposed the cultures to five common microplastic types: polystyrene, polypropylene, low-density polyethylene, poly(methyl methacrylate) and polyethylene terephthalate.
The researchers exposed the cultures to concentrations of these microplastics at levels they believed reflected the degree at which humans are typically exposed to the particles, as well as at higher concentrations for comparison.
The microplastic-treated cultures had a consistent and significant increase in acidity, the researchers said, meaning a lower pH level compared to controls, which they said indicated altered microbial metabolic activity.
After deeper investigation, the researchers found that exposure to microplastics caused shifts in bacterial composition, with some bacterial groups increasing or decreasing depending on the microplastic types, particularly bacteria that is important for digestion and overall gut health. The shifts in bacterial composition also impacted the levels of chemicals produced by the bacteria.
“Microplastics might influence the gut microbiome in a few different ways,” Pacher-Deutsch said. He said they can bind nutrients, “potentially affecting their availability to microbes,” and that chemical leachates from the plastics could act as “stressors, possibly altering microbial composition and metabolic activity.”
He added this could “contribute to more complex and less predictable changes in microbial interactions.”
Notably, the microplastic-induced changes in microbial composition reflected patterns previously linked with conditions such as depression and colorectal cancer. The researchers said that this highlighted the potential implications of microplastic exposure for disease risk.
This does not necessarily mean there is a definitive link between microplastics and depression and colorectal cancer, but rather that “the presence of microplastics can change the composition of gut-derived microorganisms,” resembling those of people suffering from depression or colorectal cancer, Rolf Halden, director of the Biodesign Center for Environmental Health Engineering at Arizona State University, told Newsweek.
He added that this new study “identifies one more potential impact of a large spectrum of potential adverse human health effects from unwanted human exposure to fragmented consumer plastics.”
Gut microbiome plays a “key role in regulating both physical and mental health,” Pacher-Deutsch said. This means that any changes in microbial composition “have been linked to conditions like depression and colorectal cancer,” he added.
He said that the finding now raises the question of whether environmental factors, like microplastics exposure, may be contributing to the increased diagnoses of both conditions in the past decade.
“While we can’t draw direct conclusions yet, these findings highlight the need for more targeted research to explore potential connections,” he added.
The Concern Of Everyday Microplastic Exposure
Given that plastics, and microplastics, are so widely used, it’s not possible to eliminate them from daily life, Pacher-Deutsch said, so instead, it’s important to “recognize its potential risks and take steps to protect public health, just as we do with other environmental hazards.”
“I am concerned about human exposure to microplastics and the lack of regulatory action, given this worldwide phenomenon of ubiquitous plastic pollution,” Halden said.
He said that the “continuous and increasing exposure” of humans to microplastics “worries me from a public health perspective.”
“The lack of regulations suggests that this ongoing human exposure is inconsequential. Yet, from a public health perspective, there is no precedent of continuous uptake of foreign particulates into the human body that does not result in some adverse health effects,” he said.
Future Implications
In light of the findings, Pacher-Deutsch said that the study “could have important implications for future medical care.”
“The microbiome is linked to a wide range of conditions, so understanding how environmental factors like microplastics affect it could help shape prevention strategies, diagnostics, and even personalized treatments,” he said.
Although, he added that “before we get there, we need much more research to clarify the biological impacts and identify who might be most at risk.”
In order to reduce exposure to microplastics, using plastic-free alternatives like wooden cooking utensils, glass bottles, and plastic-free dental care products is a start, he said, but “the most important step right now is supporting research and biomonitoring efforts.”
“Only with more data can we understand the biological impacts of microplastic exposure and develop evidence-based regulations to reduce risk,” he said.
Halden said that public education was also vital, which he said was “fast, inexpensive and potentially very impactful.”
“Paper cups lined with polyethylene, as used by many coffee chains across the nation, should state that each cup releases not billions but literally trillions of nanoplastics per serving,” he said, which a U.S. government study has shown.
Instead, he added that people should bring their own reusable cup to not only protect their own health but also to limit their contribution to the “plastic pollution crisis, which is driven to a large degree by single-use drinking containers, including plastic-lined paper cups, plastic cups, and single-use water bottles.”
Full Interview Below
Newsweek’s interview with Christian Pacher-Deutsch, lead author of the study and a Ph.D. student at the research institution CBmed GmbH and the Medical University of Graz, Austria.
Q1: Are you concerned about this finding?
“We live in a close relationship with our gut microbiome, and even subtle changes could have implications for our health. While it’s too early to draw definitive conclusions, the patterns we observed in our bioreactor experiments suggest that this is something worth paying attention to. Plastic is deeply embedded in our daily lives, so banning it entirely isn’t realistic. But like with other environmental risks, we need to recognize the potential harm and take steps to protect people. That starts with supporting biomonitoring and epidemiological studies to better understand exposure and its effects. Only with more data can we develop evidence-based regulations and meaningful protective measures.”
Q2: How can microplastics impact gut microbiome?
“Microplastics might influence the gut microbiome in a few different ways. For example, they can offer surfaces that encourage biofilm-forming bacteria, which could shift the microbial balance. They may also bind nutrients, potentially affecting their availability to microbes. Additionally, chemical leachates from the plastics could act as stressors, possibly altering microbial composition and metabolic activity. And since the bacterial food web might be influenced by these different effects, this could contribute to more complex and less predictable changes in microbial interactions.”
Q3: Why is this so important? How can gut microbiome affect a person’s risk of developing depression or colorectal cancer?
“This is important because the gut microbiome plays a key role in regulating both physical and mental health. Changes in microbial composition have been linked to conditions like depression and colorectal cancer. In our bioreactor experiments, we observed shifts in the microbiome that resemble patterns reported in these diseases. Given that diagnoses of both conditions have risen over the past decade, it raises the question of whether environmental factors, like microplastics exposure, might contribute. While we can’t draw direct conclusions yet, these findings highlight the need for more targeted research to explore potential connections.”
Q4: How much exposure to microplastics do you think poses a risk to a person’s health? How are most people being exposed to microplastics?
“At this point, we can’t say exactly how much microplastic exposure poses a health risk, but we do know that people are constantly exposed through food, water, air, and even everyday items like clothing and packaging. Some estimates suggest that weekly intake could be as high as the equivalent of a credit card, though these numbers are still uncertain. Microplastics have already been found in various parts of the human body, including the gut and bloodstream. Their widespread presence makes it clear that we need to treat plastic pollution as a serious public health issue. Biomonitoring studies and understanding long-term risks should be a priority moving forward.”
Q5: What can people do in light of this finding to reduce exposure and is there any other advice you’d give to those concerned?
“While we can’t eliminate plastic from daily life, we do need to recognize its potential risks and take steps to protect public health, just as we do with other environmental hazards. In a pilot study conducted within the microONE project, we provided participants with plastic-free alternatives like wooden cooking utensils, glass bottles, and plastic-free dental care products. Still, they found it very difficult to avoid plastic in daily life. This shows how deeply plastic is embedded in our routines and highlights the need for systemic changes and more accessible alternatives. The most important step right now is supporting research and biomonitoring efforts. Only with more data can we understand the biological impacts of microplastic exposure and develop evidence-based regulations to reduce risk.”
Q6: What do you think this finding means for future medical considerations?
“Since microplastic exposure does influence the gut bacteria, it could have important implications for future medical care. The microbiome is linked to a wide range of conditions, so understanding how environmental factors like microplastics affect it could help shape prevention strategies, diagnostics, and even personalized treatments. But before we get there, we need much more research to clarify the biological impacts and identify who might be most at risk.”