Groundbreaking research presented at UEG Week 2025 in Berlin has revealed that microplastics can alter the human gut microbiome, potentially influencing health in ways that resemble patterns linked to depression and colorectal cancer. The study is the first of its kind to use human stool samples, offering direct evidence that plastic particles smaller than 5mm can affect microbial composition and activity in the digestive system.
Microplastics trigger changes in gut microbiome health
The research, part of the microONE project led by CBmed research centre in collaboration with international partners, investigated how different types of microplastics interact with the human microbiome. Stool samples from five healthy volunteers were grown as ex vivo gut cultures and exposed to five common plastics: polystyrene, polypropylene, low-density polyethylene, poly(methyl methacrylate), and polyethylene terephthalate.
While the total bacterial count did not change significantly, the microplastic-treated cultures became more acidic, suggesting shifts in microbial metabolism. Detailed analysis showed plastic-specific changes in bacterial composition, with notable effects across bacterial families such as Lachnospiraceae, Oscillospiraceae, Enterobacteriaceae, and Ruminococcaceae. Most changes occurred within the phylum Bacillota – a critical group of bacteria for digestion and gut health.
The researchers also observed alterations in bacterial metabolites, including valeric acid, lactic acid, and lysine, depending on the type of microplastic. Some of these chemical shifts reflected patterns associated with depression and colorectal cancer, raising concerns about long-term health risks from microplastic exposure.
Implications for everyday exposure
Lead author Christian Pacher-Deutsch explained that the mechanisms remain uncertain but may involve biofilm formation on plastic surfaces, which creates new niches for microbes, or the leaching of chemicals that directly influence bacterial metabolism.
“Microplastics are everywhere – in bottled water, seafood, table salt, and even the air we breathe,” Pacher-Deutsch noted. “Our findings show they can indeed impact the gut microbiome. While we cannot yet make firm health claims, reducing exposure where possible is a sensible precaution.”
The results underline the urgent need for further research into how microplastics interact with the body, and whether their influence on gut health could contribute to disease risk.
Reference
Pacher-Deutsch, C et al. Microplastic-induced alterations in gut microbiome and metabolism: Insights from an ex vivo bioreactor model. UEG Week, 3-7 October, 2025.
