The Microplastic-Gut Microbiota Axis: A Unifying Framework Linking Environmental Pollution to Undernutrition, Obesity, and Metabolic Dysfunction.

The ubiquity of plastic pollution has rendered dietary microplastic (MP) ingestion unavoidable, introducing an unrecognized yet pervasive threat to human nutritional health. This review systematically synthesizes evidence from rodent and aquatic animal models, in vitro human gut microbiota simulations, and cross-sectional human observational studies to conceptualize the "MP-gut microbiota-nutrition axis" as a unifying mechanistic framework. Our synthesis delineates 4 interconnected pathways triggered by MP-induced gut dysbiosis: 1) disrupted energy harvest via short-chain fatty acid depletion and bile acid dysregulation; 2) compromised gut barrier integrity leading to metabolic endotoxemia; 3) impaired micronutrient bioavailability; and 4) appetite dysregulation through the gut-brain axis. These hazardous effects are amplified by Western-style diets and early-life exposure, positioning MP as a direct environmental determinant linking pollution to the triple burden of malnutrition. By critically evaluating dose relevance across >75 studies published between 2020 and 2025, this review rejects the notion of plastic pollution as a distant ecological concern and reframes it as a proximate, modifiable driver of global malnutrition requiring urgent integration into public health and policy.