Socioeconomic position and the gut microbiota: a narrative synthesis of the association and recommendations

Evidence suggests that socioeconomic position (SEP) may shape the gut microbiota (GM), representing a mechanism through which social and environmental factors may drive health inequalities, yet no systematic review has examined this association. In this narrative systematic review, we searched PubMed, Web of Science, and Scopus up to 30 November 2024 for observational studies examining associations between measures of SEP and GM diversity, composition, or function in participants of any age, ethnicity, or location. We identified 1,479 unique studies, of which 26 met the inclusion criteria for this review. Associations were observed between SEP indicators and GM features, including alpha (α) and beta (β) diversity, taxonomic composition, and functional pathways. Notably, socioeconomic patterns in α-diversity differed by context, with greater diversity observed in advantaged groups in high-income countries (HICs) but in disadvantaged groups in low- and middle-income countries (LMICs). Differences in β-diversity suggest that advantaged and disadvantaged groups have distinct GM profiles. Furthermore, considerable heterogeneity was evident across studies, particularly in sampling, sequencing, and analytical methods. Overall, socioeconomic-related differences in the GM are evident globally, highlighting the microbiota as a potential target for interventions aimed at reducing health disparities. Further research employing larger and more diverse cohorts, longitudinal designs, metagenomic sequencing approaches, and comprehensive measurement and adjustment of key covariates is needed to deepen understanding of this relationship.