The researchers compared gut microbiome of urban and rural populations in Haryana with those of people from Leh in Ladakh, the highest plateau of Jammu and Kashmir. Credit: S. Priyadarshini

Where you live shapes your gut microbial ecosystem as much as what you eat, a wide-ranging new research on Indians living in sea level cities to high altitude Himalayan villages has revealed1. This rare study of gut microbiome of Indians also identifies a population from suburb in the state of Haryana as ‘healthy guts’ and ideal donors for ‘faecal microbiota transplant’, a procedure that helps patients of Clostridium difficile infection or inflammatory bowel disease (IBD) to regain a healthy gut.

Though the diversity and basic functional attributes of the gut microbiome of Indians is not well understood, researchers from All India Institute of Medical Sciences (AIIMS), New Delhi and Translational Health Science and Technology Institute (THSTI), Faridabad have now figured that the gut of healthy Indians predominantly harbours four families of such microbes – Firmicutes (62%), followed by Bacteroidetes (24%), Actinobacteria (5.2%) and Proteobacteria (4.2%).

They peered through the gut microbiome of 84 city and village dwellers in Ballabhgarh, a suburb in Faridabad district of Haryana, 40 kilometers from Delhi, and hill folks from the rural Himalayan town of Leh in Ladakh, the highest plateau of Jammu and Kashmir. The healthiest guts were found to be in rural Ballabgarh as compared to those in adjacent urban areas. Similarly, the Leh population had much healthier gut microbiome than the urban population living near Delhi.

The THSTI scientists working on the gut microbiome project. Credit: Bhabatosh Das

The researchers detected 54 core bacterial genera across these three divergent communities and also found that the composition of these microbes was influenced by the geographical location and diet of the people studied. In Leh people studied, the microbial composition was dominated by bacteroidetes and had minimal Proteobacteria while in Ballabhgarh the guts showed high Firmicutes and Proteobacteria.

The highest microbial diversity was found among people living in rural low altitude areas. “Most importantly, the gut microbiomes from Ballabhgarh were predicted to have a high abundance of genes belonging to several pathways that degrade xenobiotics (foreign chemical substances),” says one of the corresponding authors Bhabatosh Das, an assistant professor at THSTI.

The Leh microbiota not only had the least abundance of Proteobacteria, but also a significantly high abundance of bacteria like Faecalibacterium and Lachnospiraceae that encode anti-inflammatory functions. Functions linked with the vitamin biosynthesis, energy metabolism and anti-inflammatory pathways like zeatin biosynthesis were also significantly high in the gut microbiome of Leh people, Das says.

“We have been seeing a transition of disease burden from communicable to non-communicable in India,” says co-corresponding author Vineet Ahuja, professor of gastroenterology at AIIMS. “Diseases like inflammatory bowel disease (IBD) or ulcerative colitis and Crohn's Disease – hitherto considered diseases of the Western world – are being increasingly seen in India,” he says, explaining the rationale behind the need for a detailed study of the Indian gut microbiome.

One of the possible reasons for the change in disease epidemiology and the upsurge of diseases like IBD, obesity, fatty liver could be adaptation of a western diet and lifestyle and subsequent changes in the gut microbiome, Ahuja says.

“Over the last ten years that we set up the AIIMS camp in Leh, we have never seen a single case of IBD, whereas there are hundreds of cases in Delhi. It seemed that Ladakh was insulated from noncommunicable diseases related to gut microbiome,” he adds. The study was, therefore, designed to compare who has the healthiest gut flora amongst the seemingly healthy people living in the three different ecosystems. Factors such as environment, antibiotic usage and host genetics could also play important role in shaping community structure of the gut microbiota, Das says.

Faecal Microbial transplantation (FMT), used worldwide as a standard procedure for recurrent Clostridium difficile infection, is now gaining currency in India as a therapy for IBD, according to Ahuja. FMT requires faecal donation by a healthy adult. “Some donors have a higher therapeutic success rate compared to others leading to the question – is it possible that healthy adults living in agrarian areas have healthier microbiome and hence are potentially better donors?"

The study points to the possibility of recruiting FMT donors from rural areas for better chances of success with the therapy, Ahuja says. “It also tells you that urbanisation seems to make matters worse for the gut microbiome and in a way and opens doors for the emergence of non-communicable diseases.”