Microplastics Disrupt Gut Bacteria Linked to Serious Health Risks

A recent study has revealed that microplastics, which are tiny plastic particles smaller than 5mm, can significantly alter the human gut microbiome. This research highlights potential health risks, linking changes in gut bacteria to serious conditions such as depression and colorectal cancer. Conducted by the Center for Biomarker Research in Medicine in Austria, the findings were presented during the United European Gastroenterology Week on October 6, 2025.

Microplastics have become a global health concern due to their widespread presence in the environment and human bodies. Research indicates that the average person ingests between 78,000 to 211,000 microplastic particles annually through drinking water, food, and air. These particles have been identified in extreme locations, from Mt. Everest to the depths of the Mariana Trench, as well as within human blood and organs.

The study aimed to investigate how exposure to various microplastics affects gut bacteria. Researchers utilized ex vivo gut microbiome cultures derived from stool samples of five healthy volunteers. The cultures were exposed to five common types of microplastics: polystyrene, polypropylene, low-density polyethylene, polyethylene, and polyethylene terephthalate.

The experiment assessed the impact of different microplastic concentrations, ranging from typical human exposure levels to higher doses, examining potential dose-dependent effects. While total bacterial cell counts remained relatively stable across all cultures, those exposed to microplastics showed a notable decrease in pH compared to control samples. This change indicates a metabolic alteration within the bacteria.

The research identified specific shifts in bacterial composition due to microplastic exposure. Certain bacterial groups either thrived or diminished based on the type of plastic introduced. These changes involved significant families, including Lachnospiraceae, Oscillospiraceae, Enterobacteriaceae, and Ruminococcaceae. Most alterations occurred within the Bacillota phylum, which is known for its role in digestion and maintaining gut health.

Changes in bacterial composition led to alterations in chemical production, correlating with the observed drop in pH. Compounds such as valeric acid, 5-aminopentanoic acid, lysine, and lactic acid were affected. Researchers proposed that the chemicals within microplastics could directly interfere with bacterial metabolism, prompting a stress response that alters acid production and disrupts the microbiome balance.

According to Christian Pacher-Deutsch, the study’s lead author, the precise mechanisms behind these changes remain unclear. “Microplastics may change microbial composition by creating physical or chemical environments that favour certain bacteria,” he explained. “For instance, biofilms can form on microplastic surfaces, providing new niches that some microbes colonise more rapidly.”

These observed alterations in the gut microbiome may increase the risk of diseases, as the patterns induced by microplastics resemble those associated with depression and colorectal cancer. The findings contribute to a growing body of evidence suggesting that our plastic-dominated environments could have unforeseen and potentially significant impacts on human health.

As research continues, understanding the full implications of microplastic exposure on human health will be crucial. The study serves as a significant step towards uncovering the complex interactions between microplastics and the gut microbiome, illuminating a pressing public health issue.