Decline of Fiber-Degrading Bacteria in Industrial Societies Affects Gut Health

It’s no secret that fiber plays a critical role in human health, primarily due to its positive effects on the gut microbiome. This plant-based material, primarily composed of cellulose, is essential for maintaining a balanced gut flora. However, recent research indicates that modern dietary habits, particularly in industrialized societies, are leading to a decline in important gut bacteria that thrive on fiber, particularly cellulose-degrading bacteria.

A study published in Science by researchers led by Prof. Itzhak Mizrahi from Ben-Gurion University of the Negev, along with international collaborators, highlights a concerning trend: the gut microbiomes of people in industrialized nations are losing crucial strains of bacteria like Ruminococcus, which are vital for processing dietary fiber.

Lead researcher Sarah Moraïs emphasized the historical significance of fiber in human diets, noting that it has always been a staple since our evolution and is also present in the diets of primates. Ruminococcus works by breaking down cellulose through complex structures known as cellulosomes, which act like sophisticated tools that bacteria use to convert fiber into absorbable nutrients.

According to Prof. Edward Bayer of the Weizmann Institute, the challenge of digesting cellulose is substantial given its insolubility. The process is akin to tackling a tree-trunk submerged in water—it soaks but does not dissolve, making it difficult for our bodies to absorb its benefits. However, the complex enzymatic machinery produced by Ruminococcus transforms fiber into shorter, soluble carbohydrates that can then be utilized by various gut microorganisms.

This enzymatic transformation is pivotal, as it allows the gut microbiome to access a broader range of nutrients from fiber, thereby supporting a healthy digestive system. While these cellulose-degrading bacteria are robust among hunter-gatherer populations and rural communities, they dwindle significantly in industrialized settings.

Interestingly, the research also suggests humans may have adapted beneficial bacteria from domesticated livestock throughout our history. Prof. Mizrahi pointed out that the genetic composition of some human strains of Ruminococcus share closer ancestry with those from cows and sheep than those present in our primate relatives.

This raises intriguing questions about our dietary evolution, as we seem to have adapted to incorporate livestock-related microbes in our gut, which may have been advantageous when our diets included more fiber-rich foods. Yet, with the shift towards processed and synthetic food sources, these bacteria are becoming less prevalent.

Sampling across various human cohorts has confirmed that while traditional diets still support diverse gut flora rich in Ruminococcus, Western diets—characterized by refined sugars and low fiber—are contributing to the stark decline of these essential microbes.

Prof. William Martin, an evolutionary biologist, noted that modern conveniences such as fast food and home-delivery meals are distant from the dietary practices of our ancestors, further exacerbating this loss. The team concluded that a transition away from fiber-laden foods is likely responsible for the disappearance of these crucial cellulose-degrading bacteria from contemporary human microbiomes.

The study’s findings pose an essential question: how might we counteract this decline? One straightforward recommendation emerges from both clinical and dietary perspectives—consume more fiber. Encouraging people to return to diets rich in whole foods, fruits, and vegetables could rejuvenate our gut microbiomes.

This research underscores the relationship between our eating patterns and gut health, suggesting that restoring fiber to our diets may be a key step in reclaiming the biodiversity of our intestinal flora. The implications stretch beyond mere dietary guidelines, hinting at a need for a broader reevaluation of how lifestyle changes are impacting our biological systems over generations.

For a deeper exploration of this topic, see the work of Sarah Moraïs and her colleagues in the study titled "Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans," recently published in Science.

Materials provided by Ben-Gurion University of the Negev. Note: Content may be edited for style and length.