A Review of Global Patterns in Gut Microbiota Composition, Health and Disease: Locating South Africa in the Conversation.

The gut microbiota plays an essential role in human health through its contributions to immune regulation, metabolism, pathogen defence and disease susceptibility. Despite this significance, most gut microbiome research remains disproportionately focused on high-income countries, resulting in a limited and underrepresented view of global microbial diversity. This bias is evident in Africa, where populations, including those in South Africa, show unique combinations of genetic variation, dietary patterns and environmental exposures that are insufficiently captured in current datasets but offer opportunities to uncover novel insights into microbial evolution and its influences on health across diverse settings. In response to this gap, this review synthesises global patterns in gut microbiota composition and diversity while situating South African findings within this broader context. We examine evidence across microbial domains, including bacteria, fungi, viruses, archaea, protozoa and helminths, and highlight the impact of dietary transitions and environmental exposures on microbial community structure. Although still emerging, research on the gut microbiome of South African populations consistently reports contrasts between rural and urban populations, with rural groups enriched in fibre-fermenting and anti-inflammatory taxa, whereas urban communities often exhibit reduced diversity and features of dysbiosis linked to Westernisation. However, limited sample sizes, heterogeneous methodologies and absence of multi-omic approaches constrain robust interpretation. These lacunae in current knowledge emphasise the urgent need for large-scale, longitudinal studies that reflect South Africa's demographic and geographic diversity. Strengthening this evidence will not only help identify microbial signatures linked to modifiable lifestyle factors but will also guide nutrition, prevention and screening programmes to improve health in African populations.