Microplastics May Be Altering Your Gut Bacteria, Study Finds

By now, you’ve probably heard that microplastics are everywhere. As Food & Wine previously reported, one estimate suggests that more than 170 trillion microplastic particles are currently floating on the ocean’s surface. By 2050, these plastic particles could outweigh the total weight of all fish. While scientists understand that micro- and nanoplastics are widespread, less is known about how they affect the human body. However, a new research project published in the American Medical Journal shows that they can “alter the human gut microbiome” and impact human health in ways we didn’t expect. 

In October, researchers presented their findings at UEG Week 2025, a conference that brings together “digestive health experts from around the world,” showing that microplastics not only alter our gut health but also impact our overall health in ways that “resemble patterns linked to depression and colorectal cancer,” the journal shared in a statement about the work. 

To reach this conclusion, the team examined stool samples from five healthy volunteers, which were then used to cultivate gut microbiome cultures. They then exposed them to concentrations of five common microplastics — polystyrene, polypropylene, low-density polyethylene, poly(methyl methacrylate), and polyethylene terephthalate — that reflect estimated human exposure levels. They also exposed some samples to higher doses to see if there were any dose-dependent effects on human gut health.

The team explained that the microplastic-treated cultures became more acidic, indicating changes in “microbial metabolism,” with the most notable changes occurring in the phylum Bacillota, “a critical group of bacteria for digestion and gut health.” They also observed alterations in other bacterial metabolites (chemicals produced by bacteria), which reflected patterns “associated with depression and colorectal cancer, raising concerns about long-term health risks from microplastic exposure.”

“Microplastics are everywhere – in bottled water, seafood, table salt, and even the air we breathe,” Christian Pacher-Deutsch, lead author of the study, shared. “Our findings show they can indeed impact the gut microbiome.” He critically added, “While we cannot yet make firm health claims, reducing exposure where possible is a sensible precaution.”

While the science on how these microplastics affect us is ongoing, other experts agree it’s very likely they are harmful to our health. Dr. Don Thushara Galbadage, an associate professor at Texas Christian University, previously explained to Food & Wine that smaller particles in the nanoplastic range “can cross gut barriers and have been detected in human tissues and fluids.”

He cited one study that found micro- and nanoplastics within carotid artery plaques, which are linked to a higher risk of major cardiovascular events, as a major red flag. “These findings suggest some fraction can translocate and persist, though dose, size, and polymer type matter,” Galbadage said.

Sasha Adkins, a senior lecturer in environmental health sciences at the University of Massachusetts Amherst, also noted she’s particularly focused on microplastics and the gut microbiome. “It seems from multiple lines of research that the more plastic in our gut, the more likely we are to develop inflammatory bowel disease,” she said. And while Adkins shared that many microplastics “are excreted in urine, feces, and breastmilk … enough remains that researchers find worrisome amounts accumulating in our lungs, our brain, and really anywhere they look.”