Gut-microbe study races to capture what urban diets erase in urbanising India

Not just genes, but also bacteria found in the human gut may help explain why urbanizing Indians face rising rates of diabetes, obesity and hypertension. It is the product of a three-year study that produced what its authors describe as the first reference database of the gut microbiome in South Asia.

Study published in a peer-reviewed journal Gut MicrobesHe sampled 575 adults from 10 communities in India and Sri Lanka and genetically profiled their gut bacteria. Niraj Rai of the Birbal Sahni Institute of Palaeoscience in Lucknow, who led the study along with Maanasa Raghavan of the University of Chicago, said India offers a rare natural experiment. “It’s the only country in India where you can still find rural and urban populations,” he said, coming from the same lineage but living in very different food environments.

According to the latest data from the International Diabetes Federation, there are an estimated 89.8 million adults living with diabetes in India by 2024. It is the second largest burden in the world after China, with roughly one in seven adults worldwide suffering from the disease. The federation estimates that the total number of cases in India will increase by nearly 75% to reach 156.7 million by 2050, even though an estimated 43% of cases are currently undiagnosed. It is estimated that 589 million adults worldwide have diabetes. The rapid rise of the disease in India is largely due to rapid urbanization and dietary change; The very transition that this study aims to read in the intestines.

The researchers designed their study by matching each remote, forest-dwelling or early agricultural community with relatives who had migrated to towns and cities that had access to processed foods like “pizza, chowmein, cola,” as Mr. Rai describes them. Because both groups share genetic ancestors confirmed by genome sequencing, Mr Rai argued that the differences in their microbiomes must be due to the environment rather than genes. The Veddas of Sri Lanka, who were among the region’s earliest hunter-gatherer settlers, were included because they remained genetically South Asian and maintained a foraging lifestyle that Mr Rai said was close to the “ancient gut signature”.

The clearest example of the environment reshaping the same genetics megamonasA bacterium that the study found was consistently found in greater abundance in urban individuals than in their rural relatives. Megamonas has been associated with obesity, hypertension, and high blood sugar worldwide; The article reports a significant relationship with a known mechanism involving blood sugar and lipid absorption. “This is the first time we are reporting that Megamonas has evolved due to diet change,” said Mr. Rai.

run to the other side holdemanellaThe condition, which is associated with fiber intake and glucose tolerance, is common in South Asia but has apparently disappeared with urbanization — except in Kerala, where communities largely maintain traditional diets even after migrating, Mr. Rai said.

Mr. Rai framed urbanization as a matter of food processing rather than meat-eating. In the northeast, both rural and urban communities eat meat; The urban difference is biscuits, soft drinks and occasionally pizza.

The findings also challenge the long-standing dairy calculus in the subcontinent. The lactase persistence gene, which enables adults to digest milk, is generally traced to migrations from the northwest and eventually Anatolia and the steppes about 4,000 to 5,000 years ago. But Mr Rai pointed to pastoral communities (Ladakhis, Toda and Kota, Kadu Golla) where he said milk consumers were much earlier and their intestines bore signs of bacteria capable of breaking down lactose. Screening more than 10,000 samples, the team said it found little correlation with lactase persistence genotypes. Mr Rai suggested that the mutation was an “additional benefit” rather than a necessity, and that the bacteria responsible were favorably selected at the community level over a long period of time.

Mr Rai said microbiome research was important because gut bacteria act as an environmental factor that changes how genes are expressed, comparable to how smoking increases the risk of hereditary cancer. He calculated that a person carries up to a kilogram of gut bacteria, partly inherited from their parents, and that changing this could eventually be a path to a cure.

The project is now moving into the functional phase. Mr. Rai’s team began metabolomics studies (profiling the molecules produced by these bacteria) to link specific microbes to specific diseases. It expects about 1,000 samples by the end of the year, including in the Andaman and Nicobar Islands, where the team received approval to sample isolated communities this winter. Mr Rai believes the window has closed. No one can do such a work because roads are coming everywhere now.