Eating primarily meat for too long could eventually rob us of our ability to digest plant matter, study finds

Growing up in a middle-class Indian household and exposed to American sitcoms, one learns two things about the West: their fondness for meat and their children's aversion to vegetables. However, experiencing and empathising are distinct, especially having been raised on a rich array of delightful Indian vegetarian fare, even while acknowledging our nation's meat culinary traditions. As elucidated by Zomato's CEO, India boasts the highest percentage of vegetarians globally, cementing plants as an integral aspect of our diet.

Nevertheless, for the industrialised and supposedly "developed" West, undergoing a protracted transition towards meat-centric diets, there appears to be a new challenge in the realm of gut health. Scientists have unearthed a potential repercussion of the low fibre content in Western diets, affecting the digestion of robust plant material.

Similar to other animals, our digestive systems host diverse colonies of microbes essential for breaking down food into assimilable components. However, until a study unveiled a group of relevant bacteria in 2003, human gut microorganisms capable of digesting cellulose remained elusive.

Using these bacteria as a genetic blueprint, researchers meticulously analysed human faecal samples to scrutinise the gut microbiome across various times and regions. From samples of farmers to hunter-gatherers and ancient humans dating back 1,000 to 2,000 years, no stool remained unexamined.

The researchers discovered multiple species of cellulose-digesting microbes in all these populations, akin to those found in cud-chewing mammals and other primates. Curiously, these same species were conspicuously scarce among individuals from modern, industrialised societies.

"These findings collectively suggest a decline in these species within the human gut, likely influenced by the shift towards Westernised lifestyles," explained the study’s authors. They posit that these Ruminococcus microbes may have lost access to their preferred fibre-rich diets, causing their decline among urbanites. Consequently, this may compromise humans' ability to process plant matter, exacerbating metabolic health issues.

Previous studies have highlighted the insufficient fibre intake in industrialised societies, leading to adverse health consequences. Fortunately, developing "cellulose supplements" to address this issue appears feasible, with initial research yielding promising results for human gut health. However, further investigation is imperative to fully comprehend the links between cellulose microbes and human health before our guts become inhospitable to microbial adaptation.

These research findings have been published in Science.