Microplastics can alter the gut microbiome in ways that could raise health risks, study finds

Microplastics, or tiny particles that are prevalent in the environment, could affect our gut health, a small new study has found.

They appear to alter the gut microbiome, which is the ecosystem of bacteria, fungi, and viruses that live in our digestive tracts and help protect against pathogens, stimulate our immune systems, and spur our bodies to produce vitamins.

In an experiment using stool samples from five healthy people, scientists grew microbiome cultures in a lab and then exposed them to five common types of microplastics at levels that mimic human exposure.

Microplastics did not lead to major changes in the amount of bacteria found in the cultures – but there was a significant decline in pH levels, which the researchers say indicates there had been changes to the metabolic processes that allow these microorganisms to reproduce.

The bacterial differences also varied depending on what type of microplastic was used.

“These findings are significant given how pervasive microplastic exposure is in everyday life,” Christian Pacher-Deutsch, the study’s lead author and a researcher at the Medical University of Graz in Austria, said in a statement.

Microplastics have been found almost everywhere, from the ocean and soil to beer and tea bags – as well as in human blood, saliva, livers, kidneys, and brains.

Scientists don’t know for certain how microplastics could affect human health, but exposure may affect the reproductive, immune, and cardiovascular systems.

The latest findings, which have not yet been published in a peer-reviewed journal, add to a growing body of evidence that microplastics could also affect the microbiome.

In the new study, some of the microplastic-induced changes to the microbiome cultures appeared similar to patterns linked to depression and colorectal cancer.

However, bigger studies would be needed to confirm any link, and the researchers emphasised that in people, factors such as diet, immune response, and other individual differences would also shape health outcomes.

“While it’s too early to make definitive health claims, the microbiome plays a central role in many aspects of well-being, from digestion to mental health,” Pacher-Deutsch said.

Researchers don’t yet know why microplastics appear to alter the microbiome, but Pacher-Deutsch has a few theories.

The tiny particles could create physical or chemical environments that are better for certain bacteria over others, for example. Or the chemicals in microplastics could alter the gut’s pH by directly affecting bacterial metabolism, which in turn shapes the bacteria’s growth and reactions to their environment.

“At this stage, the exact pathways remain unclear,” Pacher-Deutsch said.

Regardless, he said the findings support public health efforts to curb people’s exposure to microplastics and reduce plastic pollution.

“Reducing microplastic exposure where possible is … a wise and important precaution,” Pacher-Deutsch said.

The findings will be presented this week in Berlin, at the annual meeting of the United European Gastroenterology group.