The gut microbiome of South Asians may not simply mirror patterns documented in Western populations, as has been found by a large, geographically diverse study conducted on communities across India and Sri Lanka.
It revealed that they carry distinct microbial signatures shaped by diet, culture, geography and changing lifestyles — a finding that could have implications for how obesity, diabetes and other lifestyle-related disorders are prevented and treated.
The study, published in Gut Microbes, provides one of the most comprehensive baseline assessments of the gut microbiome among healthy South Asian adults. Researchers say the findings strengthen the case for developing region-specific microbiome diagnostics, personalised nutrition and precision healthcare, rather than assuming that discoveries made largely in European and North American populations can be applied universally.
The issue is particularly important for South Asia, home to nearly a quarter of the world's population and undergoing rapid urbanisation. At the same time, obesity, diabetes and other cardiometabolic disorders are increasing across the region.
Scientists have long known that diet, physical activity, environment and urbanisation can influence the trillions of microorganisms living in the human gut. What remained less clear was whether these changes followed a common pattern across South Asia's highly diverse populations.
The new study suggests they do not.
Researchers collected stool samples along with dietary, lifestyle and health information from 575 healthy adults belonging to 10 culturally and geographically distinct communities across India and Sri Lanka. The participants represented different environments and lifestyles, allowing researchers to examine how urbanisation and other factors were associated with changes in the gut microbiome.
Using the South Asian MicroBiome ARray (SAMBAR), developed and launched in India by scientists at the Birbal Sahni Institute of Palaeosciences (BSIP), researchers analysed the microbial composition of participants. High-throughput DNA sequencing of bacterial 16S rRNA genes was followed by bioinformatic analysis to identify patterns in microbial diversity.
The study was an international collaboration involving scientists from BSIP, the University of Chicago and institutions across India, Sri Lanka and the US. The research was led by Dr Niraj Rai, group head, Ancient DNA, BSIP, Lucknow.
Field teams worked closely with local communities to recruit participants and gather biological samples and information about their diets, lifestyles and health. Researchers also followed a community-engaged approach, sharing findings with participating communities.
The analysis revealed that each community appeared to follow its own microbiome trajectory, influenced by its local environment and way of life. At the same time, researchers identified microbial changes associated with urbanisation and metabolic health that were shared across some populations.
The distinction matters because much of the world's microbiome research has been conducted among populations in Europe and North America. South Asian populations, despite their size and considerable genetic, cultural and dietary diversity, have remained comparatively under-represented.
A microbiome shaped by a traditional South Asian diet and lifestyle, for instance, may respond differently to urbanisation, processed food, reduced physical activity or other lifestyle changes than microbiomes studied predominantly in Western settings, said the study.
This could have consequences for the emerging field of microbiome-based medicine.
The gut microbiome is increasingly being studied for its possible links with metabolic health, immunity and several chronic diseases. However, researchers caution that associations between specific microbes and disease do not automatically prove that those microbes cause the condition.
“Much more research will be needed before microbiome-based interventions become routine clinical treatment.”
Researchers said the SAMBAR resource could support future investigations into diabetes, obesity, cardiovascular disease and other lifestyle-related disorders that are becoming increasingly common across South Asia.
The findings also raise an important question about personalised nutrition. Dietary recommendations based on studies of populations with substantially different diets and microbiomes may not always produce identical responses in South Asian populations.
A regional evidence base could eventually help researchers determine whether particular dietary patterns, nutrients or interventions influence gut microbes differently across communities.
The study's significance therefore extends beyond identifying which bacteria are present in the gut. It highlights the need to understand how people, their environments and their lifestyles interact with their microbial ecosystems.
For India, the research could prove particularly valuable as urbanisation changes traditional dietary and behavioural patterns at a rapid pace. Communities that once had relatively distinct food habits and lifestyles are increasingly exposed to processed foods, sedentary behaviour and other urban influences, said the experts.
The researchers believe documenting these changes now will help scientists understand how the microbiome evolves alongside them.
