Tiny plastics may harm gut and liver health, review finds

A growing body of research suggests that microscopic plastic particles are not just an environmental concern but may also pose risks to gastrointestinal and liver health. A comprehensive review published in Clinical Gastroenterology and Hepatology brings together the latest evidence linking exposure to micro- and nanoplastics (MNPs) with inflammation, gut dysbiosis, liver disease, and possibly gastrointestinal cancers.

“While MNPs are not classified as carcinogens, they can transport toxic substances and heavy metals that increase cancer risk,” the study’s first author Priyata Dutta, MD, of the department of internal medicine at Trinity Health, Ann Arbor, Michigan, told GI & Hepatology News. “The relationship between MNP exposure and health outcomes remains unclear. As plastic pollution increases, understanding the biological effects of MNP is crucial for public health policies.”

The review examines how tiny plastic fragments, created as larger plastics break down, enter the human body through food, water, and air. Once ingested, these particles can accumulate in the gastrointestinal tract, where they interact with the gut lining, immune system, and microbiome. Microplastics are defined as particles smaller than 5 millimeters, while nanoplastics are even smaller, measured in billionths of a meter, making them difficult to detect and study.

For the narrative review, Dr. Dutta, senior author David A. Johnson, MD, chief of gastroenterology at Eastern Virginia School of Medicine, Norfolk, and colleagues screened 800 publications (from inception to February 2025) and evaluated 15 human studies, along with relevant animal and laboratory research, retrieved from PubMed, EMBASE, and Cochrane.

They analyzed data from fecal testing, tissue samples, occupational exposure studies, and experimental models to understand how MNPs may affect GI and liver health. In addition, the authors reviewed available methods used to detect these particles, noting wide variation and a lack of standardized testing. “Our aim was to start conversations between clinicians and their patients about this emerging risk,” Dr. Dutta explained.

According to the review, multiple human studies have identified microplastics in stool samples from healthy individuals, patients with IBD, and people with high occupational exposure to plastics. Several studies showed higher levels of microplastics in patients with IBD, with concentrations correlating with disease severity. The authors noted that these raise questions about whether plastic exposure contributes to inflammation or whether inflamed intestines retain more particles.

Animal and laboratory studies in the review suggest that microplastics can disrupt the gut microbiome, reducing beneficial bacteria and promoting inflammation. Some plastics may also carry harmful chemicals or heavy metals, potentially amplifying their effects. The review highlights evidence that these particles can damage the gut barrier, trigger immune responses, and increase oxidative stress — processes already known to play a role in chronic GI diseases.

The liver also appears particularly vulnerable. The authors summarize studies showing microplastic accumulation in liver tissue and associations with metabolic dysfunction–associated steatotic liver disease, fibrosis, and cirrhosis. In occupational settings, long-term exposure to certain plastics, such as polyvinyl chloride, has been linked to rare liver cancers, although these findings are based on historical cohorts and specific industrial exposures.

The review also explores emerging concerns about cancer risk, particularly colorectal cancer. While microplastics are not classified as carcinogens, the authors describe experimental data suggesting they may promote tumor growth indirectly by driving chronic inflammation, altering the microbiome, and impairing immune surveillance.

Drs. Dutta and Johnson, for the coauthors, acknowledged limitations of the review, including that most human data come from observational studies, detection methods differ widely, and there is little information on long-term exposure.

“While epidemiological evidence is strongly suggestive, further research employing environmentally relevant exposure levels, mechanistic animal studies as well as longitudinal clinical studies, appropriately balanced for risk assessment, is necessary to more precisely define the risk,” Dr. Dutta emphasized. “These findings underscore the urgent need for continued investigation, heightened awareness among healthcare providers and patients, and the development of strategies to mitigate plastic exposures and related adverse health impacts.”

Following discussions among the authors, emergent recommendations pending more conclusive evidence would be to begin with small, incremental steps, as outlined below:

• Recognize that thermal extremes accelerate plastic degradation. This includes avoiding cooking and storing food products in heat (e.g. microwave or freezing).

• Avoid or minimize single use plastic exposures (e.g. use reusable water bottles over plastics) as well as liquid commonly prepared with temperature variances (e.g. convenient plastic coffee modules as well as tea bags).

• Avoid or minimize exposure to highly processed/convenience foods, stored for long term exposure within plastics.

“Too much beyond these recommendations will not be helpful for patients at present, and potentially harmful for concerns,” Dr. Dutta and her team said. “Our job as clinicians is to make the best recommendations based on current evidence.”

The authors reported having no financial disclosures.