Home Sciences Are the microplastics that we ingest every day without knowing it harmful?

Are the microplastics that we ingest every day without knowing it harmful?


Microplastics are a global problem due to its prevalence in natural environments and in the food chain. Eight million tons of plastic end up in the oceans each year and a part ends up in the form of microparticles in the gastrointestinal tract of humans when they eat marine animals. Despite this, its impact on the human intestinal flora has not been well studied until now. A group of researchers from the Higher Council for Scientific Research (CSIC) has evaluated their potential risks in the human digestive system when eating foods that contain them. His conclusion: microplastics alter the intestinal flora and can have harmful effects on digestive health.

The ingestion of microplastics (pieces less than five millimeters) affects both the composition and the diversity of the microbial communities of the colon and alters the balance in the microorganisms present in the digestive system: decreases the presence of bacteria known for their positive effects on health and increases that of other harmful microbial groups.

These eight Spanish scientists have also shown for the first time that microplastics can be transformed during their progress through the gastrointestinal tract and reach the colon with a different shape than the initial one, according to the study, published in the journal ‘Scientific Reports’. It is the first scientific evidence of polymer biodegradation during human digestion.

The researchers simulated the complete passage of a single dose of polyethylene terephthalate (a type of plastic widely used in beverage containers and textiles) through the gastrointestinal tract, recreating the different regions of the digestive system and their physiological conditions.

Human intake: 166 mg. up to date

The doses of microplastics tested in previous research with animal models were higher than those found in edible foods and beverages, but lower than the estimated daily human intake.

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On this occasion, Spanish scientists exposed the human colonic microbiota to a concentration of microplastics closer to reality, 166 milligrams per intake of polyethylene terephthalate, which corresponds to the estimated daily intake in humans.

“It is necessary to know the fate in the body of these materials present in our day to day and the short, medium and long-term consequences,” says Victoria Moreno-Arribas, CSIC researcher and co-author of the study. “Given the possible chronic exposure to these particles through our diet, the results obtained suggest that its continued intake could alter the intestinal balance and, therefore, the health“, Add.

The authors focused the study on the changes recorded during the processes of gastrointestinal fermentation and digestion of both the morphology and structure of microplastics and the microbial communities of the large intestine colon.

To do this, the microplastics were subjected to different treatments that simulated the oral, gastric and small intestine phases of digestion, before coming into contact with the colonic flora, previously stabilized in a dynamic gastrointestinal simulator, which mimicked the impact of the digested microparticles in the complex intestinal microbial ecosystem.

In summary, our results reveal that exposure of the human colonic microbiota to microplastics affected the microbial communities presentas had been reported in animal models exposed to micro and nanoplastics, and even other nanoparticles”, the report states.

Unsuspected effects

This effect on the colonic microbiota could negatively influence human health”, the Spanish scientists warn. “The decrease in essential microbial groups for the correct balance of the intestinal microbiota and the increase in different proinflammatory and disease-related bacterial groups could alter intestinal homeostasis,” they add.

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One nuance: the study covered only one of the possible key points of impact of the ingestion of microplastics on the intestinal flora. In addition, neat polyethylene terephthalate was used, without polymer processing additives. But a large number of additives are used in plastics, “with unsuspected effects on the intestinal microbiota”the scientists point out.

“What’s more, the ingestion of microplastics could generate additional risk factors, since those from the environment could also act as vectors of possible pathogens or contaminantswhich could directly or indirectly affect the intestinal microbiota and be related to intestinal dysbiosis” (alteration of the digestive flora)stress the CSIC researchers.

Hence they point out that more research needed to elucidate the effect of the ingestion of microplastics on the balance of the ecological community of microorganisms present in the human intestine; know if they can accumulate in some organs or tissue and the consequences in the short, medium and long term; and, ultimately, assess the risk to human health.

The authors of the report are: Alba Tamargo, Natalia Molinero, Julián J. Reinosa, Victor Alcolea-Rodriguez, Raquel Portela, Miguel A. Bañares, Jose F. Fernández and M. Victoria Moreno-Arribas, from the Science Research Institute of the Food (CIAL), the Institute of Catalysis and Petrochemicals (ICP) and the Institute of Ceramics and Glass (ICV).

Reference report: https://www.nature.com/articles/s41598-021-04489-w

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