Microplastics, tiny pieces of plastic that measure 5 millimeters or less, have increasingly become a part of everyday life. From the air we breathe to the food we consume, these small particles are almost impossible to avoid. While much has been said about the environmental impact of microplastics, new research suggests that these particles may also have a significant impact on human health, particularly within the gut. A recent study has begun to unravel the potential effects microplastics could have on gut microbiota, pointing to disturbing links with gastrointestinal diseases and even colorectal cancer.
The study, still in its early stages and not yet published in peer-reviewed journals, comes from the microONE project, led by a team from CBmed GmbH in Graz, Austria. Their research explores how microplastics impact the bacteria within the human gut and the broader microbial environment. While more studies are needed, their initial findings raise significant concerns about the role of microplastics in altering gut health.
The Study’s Methodology
In order to assess the potential impact of microplastics on gut bacteria, the research team created bioreactive cultures using human stool samples. The cultures were exposed to five different types of microplastics—polystyrene, polypropylene, low-density polyethylene, poly(methyl methacrylate), and polyethylene terephthalate. These plastics were chosen because they are commonly found in the environment, and the exposure levels used in the study were meant to mimic real-world conditions, including both typical and higher-than-usual levels.
The researchers kept these cultures under controlled conditions for five days and then measured changes in the gut microbiome, focusing on bacterial counts, microbial composition, and the pH of the stool samples. They found that the pH of the cultures exposed to microplastics was significantly lower (more acidic) than the controls. A decrease in pH is often a sign of metabolic changes in bacteria, as this acidity can indicate shifts in how bacteria process and generate energy. This change in acidity was particularly concerning, as lower pH in the gut is associated with several gastrointestinal conditions, including irritable bowel syndrome (IBS) and colorectal cancer.
Microplastics and Gut pH: What the Study Found
The research team was particularly interested in how microplastics might alter the composition of gut bacteria. The human gut microbiome, a collection of trillions of microorganisms, plays a vital role in digestion, immunity, and overall health. The study showed that exposure to microplastics led to changes in the microbial composition, particularly in a group of bacteria known as Bacillota, which is one of the most common phyla in the human gut.
The findings also revealed that different types of microplastics caused varying changes in the microbial makeup. Some types of plastic led to a rise in certain bacterial populations, while others caused a decrease. These changes were linked to shifts in metabolic profiles. For example, certain types of plastics were associated with elevated levels of valeric acid, a substance produced by certain bacteria during digestion, while others were connected to lactic acid production. These shifts, although not drastic in terms of bacterial cell counts, indicated a disruption in the normal metabolic processes of gut bacteria.
Interestingly, the patterns observed in the microbial composition closely mirrored those seen in individuals suffering from conditions like colorectal cancer and depression. While more research is needed to understand the long-term implications of these shifts, this finding is concerning, as it suggests that microplastics may play a role in the development of serious health issues.
Colorectal Cancer and Depression: A Possible Link?
The association between changes in gut microbiota and colorectal cancer has been well-documented in previous studies. Gut bacteria are known to influence the immune system and inflammation, both of which are involved in the development of colorectal cancer. The study presented at UEG Week 2025 suggested that microplastics might be influencing these same pathways by altering the microbial composition in the gut.
The similarity between the changes seen in the study and those linked to depression is also significant. The gut-brain axis—the direct communication between the gut and the brain—has become an area of increasing interest for researchers exploring the roots of mental health disorders. Shifts in gut bacteria have been shown to influence mood and behavior, and disruptions in the microbiome are often seen in people with depression and anxiety. While the connection between microplastics and mental health remains speculative, this research opens up new possibilities for understanding how environmental factors, like microplastic exposure, could be contributing to mental health crises.
Potential Risks of Microplastics in the Gut
Dr. Heather A. Leslie, an independent scientist and consultant specializing in microplastics, commented on the study’s findings, noting that microplastics could interfere with the balance of the gut microbiome. “We do not want people to be inadvertently microdosing microplastics if these are interfering with the complex balance of their gut microbiota that their health depends on,” she said.
Leslie emphasized that, while the study supports the hypothesis that microplastics are not going unnoticed by the microorganisms in the gut, more research is needed to assess the long-term impacts. The current study, which exposed stool cultures to microplastics for just five days, provides valuable insights, but it does not yet address how prolonged exposure or higher doses might affect health in the long term. Furthermore, the study’s small sample size, with stool samples taken from only five individuals, means that the results should be viewed with caution.
One of the main concerns with microplastics is their potential to accumulate in the body. While a significant portion of ingested microplastics is excreted through stool, some particles may be absorbed into the bloodstream and travel to other organs, potentially causing damage. The idea that microplastics could alter the delicate balance of the gut microbiome adds another layer of concern, as disruptions in this balance have been linked to a wide range of chronic diseases.
Challenges and Limitations of the Research
Despite the compelling findings, the study has some limitations. The stool samples used in the research were taken from a small sample of individuals, and the experiments were conducted under highly controlled laboratory conditions. In real-world scenarios, diet, lifestyle, and other environmental factors would also play a role in determining how microplastics impact human health. The study also focused on a relatively short time frame, and the long-term effects of microplastic exposure on gut health remain unclear.
Furthermore, the researchers acknowledge that the potential for microplastics to affect human health is highly context-dependent. The immune system, for example, could have a significant influence on how the body responds to microplastic exposure, as could genetic factors and pre-existing health conditions. As Dr. Christian Pacher-Deutsch from CBmed GmbH noted, “Microplastic particles show an impact on the microbiome, but further research is needed to specifically look into health implications, particularly in relation to human host factors such as the immune system.”
The Need for Further Research
While the study offers valuable insights into the potential effects of microplastics on gut health, it also underscores the need for further research. The long-term consequences of microplastic exposure on human health, particularly in relation to the gut microbiome, are not yet fully understood. Future studies should focus on how chronic exposure to microplastics impacts the gut over extended periods, as well as the broader health implications of changes in microbial composition.
As the study authors themselves have noted, continued research and biomonitoring are essential to understanding the full scope of microplastic health risks. Given the widespread presence of microplastics in the environment, understanding their impact on human health is becoming increasingly urgent.
Conclusion
The emerging evidence suggesting that microplastics may alter gut health is both concerning and fascinating. While the research is still in its early stages, it highlights the importance of monitoring how these ubiquitous particles affect the delicate ecosystem of our gut microbiome. With potential links to conditions like colorectal cancer and depression, microplastics may pose a far greater threat to human health than previously understood. As research continues, it is crucial that we prioritize understanding the full impact of microplastics on our bodies and take steps to mitigate their exposure.
