Microplastics disrupt intestinal physiology: From microbiota composition to intestinal barrier integrity

Microplastics (MPs), defined as plastic particles smaller than 5 mm, either intentionally manufactured or generated through the degradation of larger plastic materials, have infiltrated the food chain and have been detected in various human biological samples. Among the possible exposure routes, ingestion appears to be the primary one; however, the mechanisms by which MPs may cross the intestinal barrier-such as transcytosis, uptake by Microfold Cells, persorption, and barrier dysfunction-and disseminate throughout the body remain poorly understood. In addition to their potential direct toxicity, stemming from their ability to carry plastic additives and adsorbed environmental pollutants, an increasing body of evidence indicates that MPs can disrupt intestinal physiology through multiple mechanisms once they reach the intestinal lumen. The aim of this narrative review is to gather and critically analyze current evidence regarding the effects of MPs on gut homeostasis, with particular focus on the mechanisms underlying their interactions with the gut microbiota and the intestinal epithelial barrier. The findings indicate that MPs pose an emerging challenge to intestinal physiology, being capable of disrupting gut homeostasis by reducing short-chain fatty acid-producing bacteria while promoting proteolytic and pro-inflammatory taxa. These alterations ultimately compromise intestinal barrier integrity.