Microplastics are ubiquitous in the natural environment, water, air and, ultimately, in what we eat. In fact, the latest estimates indicate that each person could ingest between 0.1 and 5 g of microplastics per week via food and beverages. However, despite the current concern of the population and the scientific community about the presence of microplastics in the food chain, their health impact is currently unknown. There is a need to investigate the fate in the human body of these daily use materials and their consequences, both in the short and medium-long term.
A recent study carried out at CSIC and published in the journal Scientific Reports has evaluated for the first time the impact of microplastics ingestion on the digestive tract and the human intestinal microbiota. This study focuses on micrometric polyethylene terephthalate (PET), a widespread plastic; this protocol will soon be extrapolated to study other types of plastic and particle sizes, with the overarching goal of contributing to our current understanding of the impact of micro- and nanoplastics and associated additives on the human body and how it correlates with the modification of these materials at a molecular scale.
An interdisciplinary team, with the participation of the Institute of Ceramics and Glass (ICV) and the Institute of Catalysis and Petrochemistry (ICP) and coordinated by researchers from the Institute of Food Science Research (CIAL), has designed a protocol for simulating the ingestion and digestion of microplastics under physiological conditions using the internationally validated in vitro model of gastrointestinal digestion simgi®, which hosted the human colonic microbiota during the intervention with microplastics. Combined electron microscopy and microRaman observations were used to monitor the structural and morphological changes of microplastics during digestion. For the first time, ingested micrometric PET is demonstrated to undergo biotransformations throughout the gastrointestinal tract, reaching the colon with significant structural modifications; a reduction in the bacterial diversity of the colonic microbiota, especially in the distal colon, is concomitant with such PET transformations. Specifically, the Firmicutes/Bacteroidetes ratio and the relative abundance of genera known for their positive effect on health were reduced, while other intestinal microbial groups related to pathogenic activity increased. Moreover, the microplastic analysis at the colonic stage showed the adhesion of the microbiota to the PET surface, which has not been shown before, thus, promoting the formation of biofilms.
This research helps us understanding one of the possible effects of microplastics ingestion on the digestive tract and the microbiota, given the chronic exposure to these particles through the diet. The results suggest that gastrointestinal digestion could affect microplastics and that their continued intake could alter human intestinal homeostasis and, consequently, health. The study also suggests the possible existence of taxa in human microbiome that could degrade plastics. The understanding of these mechanisms and factors, which are just starting to be investigated, will contribute to evaluate the risk of microplastics if they can remain in the human body and accumulate in organs and tissues.
This work is a collaboration between different CSIC institutes (CIAL, ICP and ICV) within the framework of the SusPlast platform and the European project on the study of the effects of micro and nanoplastics in human health PlasticsFatE (GA 965367), part of the European research cluster to understand the health impacts of micro- and nanoplastics CUSP.
Tamargo, A.; Molinero, N.; Reinosa, J.; Alcolea-Rodriguez, V.; Portela, R.; Bañares, MA.; Fernández JF; Moreno-Arribas, M.V. PET Microplastics Affect Human Gut Microbiota Communities During Simulated Gastrointestinal Digestion. First Evidence of Plausible Polymer Biodegradation During Human Digestion. Scientific Reports, 2022, 12:528 | https://doi.org/10.1038/s41598-021-04489-w
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