Tiny fragments of plastic are increasingly difficult to avoid. As larger plastic items break down, they form microplastics and even smaller nanoplastics that can end up in drinking water and foods packaged in plastic. While human exposure is widely assumed to be ongoing, scientists still know relatively little about how these particles affect digestive health over time.
A new study from researchers at INRAE adds important nuance to that picture, suggesting that the biological effects of nanoplastics may depend in part on diet. The findings, published in Environmental Science Nano, show that low-dose exposure to polystyrene nanoplastics altered gut and liver function in mice, with different outcomes depending on whether the animals consumed a standard diet or a Western-style diet high in fat and sugar.
To address limitations in earlier research, the scientists created additive-free polystyrene nanoplastics in the laboratory, allowing them to isolate the effects of the plastic particles themselves rather than chemical additives often found in commercial plastics. The particles were labeled with gold so researchers could track their presence in the body. Mice were exposed to nanoplastics in their drinking water for 90 days at three dose levels and were fed either a standard mouse diet or a Western-style diet during the exposure period.
The researchers found that even at low doses, nanoplastics altered digestive system function in ways that depended on diet. In the gut, barrier integrity was disrupted, an effect that was stronger in mice consuming the Western-style diet. At the same time, changes in gut microbiota composition were more pronounced in mice eating the standard diet, suggesting that baseline dietary patterns may influence how the gut ecosystem responds to environmental exposures.
In the liver, nanoplastic exposure disrupted fat metabolism regardless of diet. However, glucose intolerance was more pronounced in mice consuming the Western-style diet. These metabolic changes occurred even though the nanoplastics did not appear to cross the gut barrier, indicating that indirect mechanisms, such as inflammation or altered gut signaling, may play a role. The observed changes were also associated with greater weight gain in exposed mice.
Taken together, the findings suggest that nanoplastics do not act on the body in isolation. Instead, their effects appear to interact with existing dietary patterns, amplifying some outcomes while altering others. This interaction may help explain why previous studies on plastic exposure have produced inconsistent results and why health impacts may vary across populations.
The study does not suggest that nanoplastics alone cause disease, nor does it establish direct health risks for humans. Like much research in this area, the work was conducted in animals, and translating these findings to people requires caution. The doses and exposure conditions were controlled, and human exposure patterns are likely more complex and variable.
Still, the results highlight a broader point relevant to everyday eating. Diet quality shapes the gut environment, metabolism and resilience of digestive tissues, which in turn may influence how the body responds to unavoidable environmental exposures. A Western-style diet high in fat and sugar appeared to magnify several of the negative metabolic effects observed in this study, reinforcing evidence that dietary patterns can interact with non-nutritional stressors.
As nanoplastics continue to be detected in food and water, understanding these interactions may become increasingly important. Rather than framing plastic exposure as a standalone threat, the findings suggest that overall metabolic health and dietary context may play a meaningful role in shaping risk.
This research was supported by the National Research Institute for Agriculture, Food and Environment (INRAE), including a PhD grant from INRAE’s AlimH Division. Additional funding was provided by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) through the NanoPlastX project. The authors also acknowledged technical support from multiple INRAE imaging, transcriptomics and zootechnical research platforms.