Mouse study reveals harmful effects of polystyrene nanoplastics in food and beverages

Results from a new animal study suggest that microscopic plastic particles found in food and beverages may affect glucose metabolism and harm organs such as the liver. The findings raise concerns about potential health risks in people and point to the need for more research.

As plastic breaks down, it forms micro- (<5 mm) and nanoparticles (<100 nm), which can enter the food chain and end up in seafood and other foods people eat. Studies estimate that a person may ingest around 40,000 to 50,000 microplastic particles a year through food and beverages, with some estimating exposure to be as high as 10 million particles per year.

With the growing concern around micro- and nanoplastic exposure, we wanted to evaluate the impact of this exposure on health. Our observations that oral ingestion of polystyrene nanoplastics contributes to glucose intolerance and signs of liver injury, confirm and extend what has been recently reported on the effects of nanoplastics in animal models."

Amy Parkhurst, doctoral candidate in the laboratory of Fawaz George Haj, PhD, at the University of California, Davis

Parkhurst, who is also a Clinical and Translational Science Center TL1 research fellow at the University of California, Davis, will present the findings at NUTRITION 2025, the flagship annual meeting of the American Society for Nutrition held May 31–June 3 in Orlando.

For the new study, the researchers focused on exposure via oral consumption to mimic nanoparticles found in food and drink. They gave 12-week-old male mice a standard rodent diet with a daily oral dose of polystyrene nanoparticles. Polystyrene is a widely used plastic commonly found in food packaging and products. The researchers chose a daily nanoparticle dose of 60 mg per kilogram of body weight, based on human exposure levels and earlier mouse studies that showed health effects at similar amounts.

"We can't control for all the plastics the mice are exposed to," said Parkhurst. "However, our study design allowed us to see dose-correlated changes since the nanoplastics-dosed group would have a higher exposure."

Compared to the control group receiving no polystyrene, the mice consuming nanoplastics exhibited systemic glucose intolerance and elevated alanine aminotransferase, which indicates liver injury. In the mice consuming polystyrene, the researchers also observed an increase in gut permeability and elevated levels of endotoxin, which contribute to liver dysfunction.

"Our findings warrant further studies to help inform policy around micro and nano plastics," said Parkhurst. "Robust scientific evidence plays a key role in shaping monitoring efforts and guiding regulations."

The researchers are continuing to study the impact of nanoplastics on other tissues. They would like to perform more studies in rodent models to better understand the tissues and organs affected by nanoplastics and the underlying molecular mechanisms involved.

They are also working with Elizabeth Neumann, Ph.D., at the University of California, Davis, to use matrix-assisted laser desorption/ionization mass spectrometry imaging for high-resolution monitoring of nanoplastic bioaccumulation and evaluation of the ensuing tissue-specific metabolic changes.

Parkhurst will present this research at 4:48 – 5 p.m. EDT on Sunday, June 1, during the Climate, Health, and Nutrition session in the Orange County Convention Center.