Urbanization is driving significant changes in the gut microbiome across diverse South Asian populations, according to a study published in Gut Microbes on Jul. 22. The research analyzed how shifts from rural to urban lifestyles affect the community of microorganisms inhabiting the digestive tract among adults from ten geographically and culturally distinct communities in India and Sri Lanka.
The study was conducted by an international team of researchers from India, the United States, and Sri Lanka as part of the South Asian MicroBiome ARray (SAMBAR) project. The cohort included 575 adults representing Spitians from the Indian Himalayas; Gond, Kolam, and Koya from Central India; Kani from South India; Mizo and Pochury Naga from Northeast India; as well as Adivasi, urban Sinhalese, and urban Sri Lankan Tamil communities. By recruiting both rural and urban participants within these groups, researchers aimed to determine whether gut microbiome changes due to urbanization followed similar or distinct patterns across different populations.
"Establishing SAMBAR required extensive fieldwork across India and Sri Lanka, bringing together researchers, local collaborators, and participating communities spanning ten geographically and culturally distinct populations," said Nagarjuna Pasupuleti, PhD, one of the first authors who led field operations. "These collaborations were fundamental not only to making this study possible but also to ensuring that study findings were returned to participating communities through accessible presentations and discussions."
The findings indicate that geography and community affiliation explained more variation in gut microbiome composition than rural or urban lifestyle alone. Although all communities showed some impact of urbanization on their gut bacteria—such as decreased diversity or increased presence of certain genera like Megamonas—the magnitude and nature of these changes differed between groups due to variations in diet, environment, and cultural practices.
"By studying rural and urban participants from multiple communities, we could ask not only whether urbanization changes the gut microbiome but whether that transition unfolds similarly across populations," said Shreya Ramachandran, PhD. "We learned that South Asian communities are heterogeneous...and respond to urbanization in different ways." Specific associations between bacterial genera such as Bifidobacterium with wheat or yogurt consumption were observed, along with unique links like higher Bacillus abundance among Pochury participants who consume fermented soybean condiments.
Researchers compared SAMBAR data with global datasets showing that South Asian microbial profiles occupy a unique position worldwide. Niraj Rai, PhD, said, "South Asia is undergoing rapid...urbanization alongside a growing burden of cardiometabolic disease. Understanding how the gut microbiome changes during these transitions will be essential for interpreting future links between lifestyle...and health." Maanasa Raghavan added: "Resources like SAMBAR help broaden that perspective by bringing historically underrepresented populations into global microbiome research." The authors hope SAMBAR will support further studies on how changing environments influence health throughout South Asia.
