Impact of microplastics on the human gut microbiome: a systematic review of microbial composition, diversity, and metabolic disruptions

Abstract

Global plastic waste production remains a critical environmental issue. Microplastics (MPs), plastic particles less than 5 mm, are now pervasive across ecosystems. Humans are exposed to MPs via ingestion, inhalation, and dermal contact raising concerns about their health impacts. This systematic review investigates the influence of MPs on the human gut microbiome, focusing on changes in microbial composition, diversity, and metabolic pathways based on 12 studies identified through Scopus and PubMed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Findings show that exposure to MPs such as polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polylactic acid (PLA), induces gut dysbiosis, marked by a loss of beneficial genera, and enrichment of pathogenic species. MPs also impair short-chain fatty acid (SCFA) production, alter metabolic functions, and modulate immune pathways, contributing to intestinal diseases, metabolic syndrome, and chronic inflammation. The extent of disruption is influenced by MP-specific properties such as type, size, and concentration. These results suggest that MPs are emerging environmental risk factors with tangible implications for human health. To fully understand the health concerns associated with MPs long-term, human-relevant studies with standardized methodologies are urgently needed to define safe exposure levels and guide policies aimed at reducing MP-related health risks.

Keywords: Dysbiosis; Gut Microbiome; Intestinal health; Microbial diversity; Microplastics.

Fig. 1

PRISMA flow diagram of this systematic review. The diagram illustrates the study selection process in accordance with the PRISMA 2020 guidelines. The flowchart presents the number of records (n = 320) identified through database searching and other sources, the number of duplicates removed, the records screened, assessed for eligibility, and the final number of studies (n = 12) included in the qualitative and/or quantitative synthesis. The reasons for exclusion at each stage are documented to ensure transparency of the selection process

Fig. 2

Summary of the impact of MPs on gut microbial metabolic pathways nad functions, emphasizing the type-specific impact of MPs and their downstream physiological consequences. The figure illustrates the downstream effects of MPs (e.g. PE, PCL, PLA, PET) in the GI tract following ingestion. [Red arrows (↑/↓) indicate increases or decreases in microbial species, metabolic output, or host response. Blue rounded boxes label specific MP types associated with observed effects. Green rounded boxes represent specific microbial taxa that are either increased or decreased in response to MP exposure.] (Fig. 2 was created using Biorender)