In a recent study, researchers show that Indian guts harbour a unique microbial population compared to other countries, and that the diverse diets within the country are associated with different gut microbes.

“Diet has been known to be the key driver in shaping the gut microbiome. Indian population has diverse lifestyles and food habits and so far, the Indian gut genome is not well explored,” states Vineet Sharma, scientist at Indian Institute of Science, Education and Research (IISER) Bhopal and a member of the research team who performed the study. India also has the highest prevalence of diabetes in the world, with 53% of deaths in India attributed to diabetes and cardiovascular diseases. India thus presents an interesting case study to understand the interplay between gut, diet, and health. 

In this first ever large-scale study, Sharma and colleagues analysed the microorganisms in gut of 110 healthy individuals to uncover the microbial diversity in India. The researchers sampled individuals from two locations with distinct diets: Bhopal in the North-Central region and Kerala from the southern part of India. The Bhopal population predominantly consumes a carbohydrate-rich diet, including plant-derived products, wheat and trans-fat food (high-fat dairy, sweets and fried snacks), whereas, the Kerala population commonly consumes an omnivorous diet comprising rice, meat, and fish. 

Researchers collected faecal samples from the volunteers, froze it within 30 min of collecting, and used it to sequence the microbiome (the combined genetic material of all the microorganisms present in a sample). A common method used for such purpose is sequencing of 16S rRNA gene. This gene consists of a region that is variable in different microorganisms, allowing the classification of different microbes. Using this analysis, the researchers found a total of 943,395 genes that were unique to the Indian microbiome.

The microbiome of Indian population was also compared to the microbiome of other countries, such as USA, China, and Denmark. ​“One of the most interesting results was the much higher levels of Prevotella species in Indian gut microbiome compared to the other populations,” says Sharma. Prevotella has been previously observed in communities that consume a plant-rich diet and is associated with vegetarianism.

The differences in the microbial population within the country were also studied. The microbiome of participants from Bhopal was enriched in species from genus Prevotella, while the same from Kerala was enriched in species of Bifidobacterium, Ruminococcus, Clostridium and Faecalibacterium.

The authors propose these differences could arise due to the differences in the diet of the two locations. Using a method that annotates functions to genes, they showed that the Bhopal microbiome was enriched in genes involved in breaking down plant polysaccharides, while Kerala microbiome had genes involved in degrading lipids and proteins, indicating its animal-based diet.

Metabolites are small molecules produced during metabolism and can reveal insights on lifestyle and metabolic changes. An analysis of metabolites in the faeces showed a high concentration of saturated fatty acids and branched chain fatty acids in Bhopal microbiome, while the Kerala microbiome had short chain and medium chain fatty acids, presumably due to the high consumption of coconut oil in Kerala.

“Both branched chain fatty acids (BCFA) and short-chain fatty acids (SCFAs) play an important role in the maintenance of health and elevated concentration of BCFAs may trigger the progression of different diseases,” says Bhabhatosh Das, a scientist at the Translational Health Science And Technology Institute (THSTI) who was not associated with the study.

It is known that the north-Indian population is predisposed towards diabetes and cardiovascular diseases. Further studies like these on diabetic and obese individuals can provide more insights into such predispositions towards diseases.