Researchers discover harmful impacts of microplastics on gut health

28 Nov 2022 --- As micro(nano)plastics (MNPs) are more commonly found in the food chain, human intake is regularly increasing. Researchers have discovered adverse health effects due to MNPs and their degraded products on the human gut microbiome, according to a recent study.

Published in the Microbial Biotechnology journal, the study found that plastics have been detected in most categories of consumed foods, drinking water and human feces. Therefore, the researchers stress that oral ingestion becomes the primary source of exposure to MNPs, and the gastrointestinal tract, primarily the gut, constantly interacts with these small particles. 

The data shows that after oral exposure, MNPs have a harmful impact on gut microbiota in a wide range of aquatic and terrestrial animal and mouse models, promoting intestinal dysbiosis, metabolic perturbed functions and an inflammatory gut environment, as well as systemic effects, of which the long-term consequences are still unclear. 

Synthetic plastics are at the top of the list of ever-accumulating pollutants, negatively affecting life on the planet. The research shows that a global annual production rate of 1,100 metric tons of pristine plastic is expected by 2050.

Microbiota disruption 
The scientists highlight that multidisciplinary research initiatives are needed to support health policy decision-making and mitigation strategies. Humans are exposed to MNP particles daily, and their intake through the food chain and drinking water represents a substantial source of exposure. 

The gut microbiota disruption can therefore be an essential biomarker for MNP toxicological assessment, assert the researchers. In recent years, different examples of the impact of plastic degradation metabolism through bacteria and the gut microbiota of insects are gaining attention in the context of bioremediation. 

The researchers say that so far, there is no clear link between MNPs’ microbial degradation and human gut microbiota regarding the specific ecological advantage and biological significance.

However, additional studies in physiologically relevant advanced in vitro models suggest MPs suffer fragmentation and biotransformation during the digestive transit, which implies members of the human intestinal microbiota, whose derived small particulate forms and released additives synergistically, might enhance MNPs’ adverse physiological effects. 

Therefore, deciphering the extent to which gut microorganisms diversify, MNP-keystone species, specific mechanisms, and biological consequences will become important to understand human response to exposure of MNPs through diet. 

Routes of micro(nano)plastic exposure to humans and their impact on the gut microbiota (image credit: Microbial Biotechnology).Further research needed
Although more research is needed on human-like conditions, increased in vitro and in vivo evidence implicates the gut microbiome presents a key challenge for the connections between MNPs and human health, which also implies environmental health and its relationship to human habits. 

The researchers say that the extent of MNP ingestion and their metabolic fate must be evaluated, requiring detailed knowledge of numerous plastics under realistic human life conditions. These include material composition, size, shape, surface properties, exposure levels, quantities and their ability to be absorbed in the gut and cause systemic toxicity in the human body. 

They conclude that understanding the complex interconnectedness between MNPs, the microbiome, and host will advance with new modeling systems, technology development, refinement, and mechanistic studies focused on the contribution of human health and microbial metabolism and ultimately provide links to sustainable food systems and planetary health. 

Relatedly, researchers at the Università Politecnica delle Marche in Ancona, Italy, detected microplastic in human breast milk. The evidence of microplastics in human breast milk, coupled with the previous discovery in the human placenta in 2020, represents “a great concern,” impacting “extremely vulnerable” infants, said the study authors. 

Edited by Natalie Schwertheim