Tiny pieces of plastic that find their way into human intestines can adversely impact the healthy bacteria and other microbes that naturally live there, known as the gut microbiome, laboratory experiments suggest.
Some of the microplastic-induced changes in gut microbes observed in test tubes were similar to changes seen with depression, colorectal cancer, and other diseases, researchers reported at the ongoing United European Gastroenterology (UEG) Week meeting in Berlin.
Earlier studies have found microplastics in stool samples and colon biopsies in a significant proportion of volunteers.
The new study used stool samples from five healthy volunteers to grow gut microbiome cultures in the lab. The cultures were then exposed to five common types of microplastic particles at concentrations reflecting estimated human exposure.
For the most part, total bacterial counts did not change. However, the microplastic-treated cultures showed significant drops in pH levels, indicating altered microbial metabolic activity, researchers found.
They also saw microplastic-specific shifts in bacterial composition, with certain bacterial groups increasing or decreasing depending on the microplastic type.
Shifts in bacterial composition were accompanied by changes in bacterial production of chemicals that nourish intestinal cells, aid in digestion of food and processing of medications, and influence mood and brain function.
The researchers don't yet know how microplastics induce these effects. And their study did not look at long-term effects of microplastics exposures on gut bacteria, nor did it consider the effects of additional factors like diet and immune response.
"The key takeaway is that microplastics do have an impact on our microbiome," study leader Christian Pacher-Deutsch of the Medical University of Graz, Austria said in a statement.
"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. Reducing microplastic exposure where possible is therefore a wise and important precaution," he concluded.
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