To what extent do microplastics, which accumulate in massive quantities in all ecosystems and in the human food chain, disrupt our bodies and threaten our health? Science is beginning to get a sense of this. Research presented at the European Gastroenterology Congress (UEG) and conducted by Cbmed, an Austrian research center, has notably highlighted for the first time the impact of microplastics on the bacteria in our gut.
Researchers analyzed stool samples from five healthy volunteers and cultured the microbiomes they contained. These bacterial cultures were then exposed to various common microplastics—polystyrene, polypropylene, polyethylene, and terephthalate—at concentrations similar to those to which humans are exposed in their daily lives.
The result: generally speaking, microplastics do not affect the total concentration of microbiomes. There are just as many bacteria afterward as before. However, when we examine the detailed composition of the different species, the differences become striking.
Microplastics disrupt the pH balance of bacterial flora.
The first indication of this disruption: when bacterial flora are exposed to microplastics, researchers have notably noticed an increase in the acidity of the environments, a sign of major changes in the composition of the populations.
By extending their analysis, they observed an increase or, conversely, a decrease in certain species depending on the microplastics to which they were exposed. Several bacterial families were involved: Lachnospiraceae, Oscillospiraceae, Enterobacteriaceae, Ruminococcaceae, the majority of them belonging to the phylum of Bacillota, a key group of bacteria for digestion and the overall health of our gut.
These disruptions in the composition of bacterial families are therefore accompanied by changes in the molecules released by the bacteria, which affect the acidity of the microbiomes.
A major impact, from the stomach to the brain
The researchers couldn't help but notice that some of these imbalances corresponded to those found when analyzing the microbiomes of people suffering from depression or a colorectal cancer.
At this stage, researchers are still unable to define the reasons for such microbial variations in response to exposure to microplastics. It seems that these microplastics create chemical or physical environments that favor some species and hinder others. For example, they mention biofilms, these clusters of bacteria, which form on the surface of these pollutants, creating very stable and prolific niches. Furthermore, these microplastics, resulting from the degradation of packaging and various objects, carry with them chemical molecules that can also have a direct influence on bacterial metabolism.
Even though this initial result is only preliminary, it demonstrates the impact of microplastics, which are found everywhere: in the oceans, soil, clouds, animal stomachs, and our own. It's no wonder their impact on our health can be so widespread and that the bacteria in our gut flora are among the first victims.
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