Microplastic-Fed Mice Develop Glucose Intolerance

We all have microplastics in our bodies. Ten years ago, that fact would have been enough to alarm most people. Now, the issue of plastic contamination is so familiar it’s even become a source of humor; flippant memes are shared on social media. The joke these days is that boomers are full of lead, Gen X full of asbestos, Millennials full of microplastics. What was once frightening is now the accepted pollution of a new generation.

But have we become too comfortable with our plastic contaminants? Should we not be more concerned about their potential effects? Perhaps, suggests one new study.  

According to Amy Parkhurst, a doctoral candidate at the University of California, Davis, micro- and nanoplastics could be damaging our livers and increasing our chances of developing glucose intolerance.

Microplastic mice

Concerned about the effects of the tiny plastics in our food, Parkhurst developed a study to test the consequences of oral administration of microplastic in mice.

Over 7 weeks, a group of 12-week-old male mice were administered with a 60 milligram per kilogram dose per day (mg/kg/day) of a solution that was 10% polystyrene, while a control group were not injected.

"We decided to focus on exposure via oral consumption (mimicking NP [nanoplastic] on food and drink)," Parkhurst told Technology Networks. "We chose to use polystyrene as it is one of the three major types of plastics and is commonly used in food packaging and products."

"Throughout the study, we gave a daily dose of polystyrene NP at 60mg/kg/day (per animal body weight per day) via oral gavage (oral consumption) to ensure proportionate exposure, while control animals received the same amount of volume of vehicle per their weights for seven weeks."

Glucose tolerance, endotoxin and gut permeability tests were performed between week six and seven.

Compared to the control group, the mice fed polystyrene exhibited systemic glucose intolerance and elevated alanine aminotransferase, an indicator of liver injury. These plastic-fed mice also displayed an increase in gut permeability and elevated levels of endotoxin, which contributes to liver dysfunction.

Parkhurst concluded that both microplastics and nanoplastics can contribute to hepatic dysfunction, though she cautioned that further research will be needed to draw firm parallels with humans.

“Many questions still remain about how nanoplastics may be affecting health," she told Technology Networks. "However, we found in our study that nanoplastic treated mice showed glucose intolerance, liver injury and increased gut permeability. Thus, more research is still needed around nanoplastics, as it is possible that nanoplastics are one of the many factors that contribute to human metabolic disease."

Parkhurst presented her findings at Nutrition 2025, the annual meeting of the American Society for Nutrition held May 31–June 3.

Expert reaction

But while many experts are concerned about the potential effects of microplastic contamination, not every expert was concerned about Parkhurst’s findings.

“While we only have the press release and abstract to go on, the keywords are ‘in mice’,” said Oliver Jones, a professor of chemistry at RMIT University. “Mice are not mini-humans; we can’t assume the result would automatically translate to humans.”

In a statement to the UK’s Science Media Centre, Jones estimated the doses used in Parkhurst’ study were equivalent to an 80 kg human eating half a gram of plastic per day.

“This is just not a realistic dose,” he said. “Recent independent review suggests that we ingest only 0.0000006 g of plastic per day. Even then, they likely pass straight out again as the gut wall is relatively thick and well-regulated in humans.”

“The mice were also force-fed this diet directly into the stomach for 6–7 weeks before the biochemical analysis was performed. If I were force-fed almost 0.5 grams of plastic a day for 6–7 weeks, I expect I would have some sort of metabolic response, but that would not necessarily be bad in itself, and in any case, this just isn’t what happens in real life.”

Jones also critiqued the type of mouse model (C57/B6J) used in the study.

“Another issue is that the type of mouse used may have problems with glucose metabolism under normal circumstances anyway,” he said. “Metabolic analyses also only give you an idea of what was happening at the single point in time the sample was taken. We don’t know if the metabolic changes were permanent or went back to normal later.”

Ultimately, Jones considered the study unhelpful when it comes to understanding the effects of microplastics on humans.

“I don’t think this study is helpful for human risk assessment,” he said. “It uses unrealistically high amounts of a plastic, which is not the major type found in the environment, fed to a type of mouse prone to glucose issues, in an unrealistic manner.”

Reference: Parkhurst A, Hsu MF, Haj FG. Adverse effects of nanoplastics administration on the metabolic profile and glucose control in mice. Nutrition Conference 2025. Accessed June 4, 2025: https://www.dropbox.com/scl/fi/5vqxu1iys1usfbj928do6/Parkhurst-abstract.pdf?rlkey=bnt3kpawmej4vyxzt0wctny58&e=1&dl=0

About the interviewee:

Amy Parkhurst is a doctoral candidate at the University of California, Davis.

*This article is based on research findings that are yet to be peer-reviewed. Results are therefore regarded as preliminary and should be interpreted as such. Find out about the role of the peer review process in research here. For further information, please contact the cited source.

*This article was updated on June 16, 2025, to include responses from Amy Parkhurst.