Microplastics in food production systems: Sources, exposure pathways, and gastrointestinal health effects

Microplastics (MPs) and nanoplastics (NPs) have become ubiquitous contaminants in food production systems, raising increasing concerns regarding their potential effects on gastrointestinal and systemic health. This review summarizes current evidence on the occurrence, sources, and biological effects of MPs/NPs within food production chains and their implications for the human gut. Experimental in vitro studies demonstrate that MPs/NPs can induce oxidative stress, inflammation, genotoxicity, metabolic dysregulation, and epithelial barrier dysfunction, while in vivo animal studies show disruption of gut homeostasis, microbiota alterations, systemic translocation, and hepatic, metabolic, and immune disturbances. Co-exposure to environmental pollutants and food-associated chemicals may further enhance toxicity through synergistic mechanisms. Although human evidence remains limited, MPs have been detected in human tissues, including the liver, indicating the possibility of systemic exposure. Emerging evidence also suggests complex interactions between MPs/NPs and the gut microbiome, although the clinical significance of these findings remains uncertain. Therefore, current knowledge is derived predominantly from experimental models, and substantial uncertainties remain regarding human exposure levels, dose-response relationships, and long-term health consequences. Further well-designed human studies and standardized exposure assessment methods are essential to clarify the health risks associated with dietary MPs/NPs.