Apr 13, 2024 20:00:00

Research results show that people living in urban areas are losing 'gut bacteria that break down dietary fiber'

Cellulose , the main component of plant cell walls and the majority of dietary fiber , cannot be broken down by human digestive enzymes, but it is known that some intestinal bacteria can break down cellulose. A new study has found that intestinal bacteria capable of breaking down cellulose are being lost from people living in modern urban areas.

Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans | Science
https://www.science.org/doi/10.1126/science.adj9223

Boosting gut health: Fiber-degrading microbes in modern diets - The Jerusalem Post
https://www.jpost.com/health-and-wellness/nutrition/article-792662

Scientists find people living in urban areas and cities are becoming less able to digest plants | Euronews
https://www.euronews.com/health/2024/03/21/gut-bacteria-to-digest-fibre-less-present-in-industrialised-societies-study-suggests

Humans Living in Cities Are Slowly Losing Their Ability to Digest Plants: ScienceAlert
https://www.sciencealert.com/humans-living-in-cities-are-slowly-losing-their-ability-to-digest-plants

Dietary fiber is a general term for food components that are difficult to digest by human digestive enzymes, and most of it is cellulose, which makes up the cell walls of plants. Although it is not directly absorbed by the human body, a study in 2003 discovered human intestinal bacteria that break down cellulose, and at the time of writing, it was found that some intestinal bacteria break down dietary fiber and the products are absorbed by the human body, and that dietary fiber helps maintain a good balance of intestinal bacteria.

In a new study, researchers from Israel's Ben-Gurion University of the Negev and the Weizmann Institute of Science analyzed a variety of gut bacteria samples to investigate the cellulose-breaking properties of human gut bacteria.

The samples included gut bacteria from modern humans of various cultures, feces left by humans from about 1,000 years ago, non-human primates , and various ruminant animals .

The analysis revealed three previously unknown species of gut bacteria

from the genus Ruminococcus , which produce an enzyme complex called cellulase when they come into contact with plants, allowing them to break down cellulose.

'Breaking down cellulose is not an easy task, and very few bacteria can do it,' said study co-author Professor Edward Bayer of the Weizmann Institute of Science. 'Cellulose is insoluble, which makes it difficult to digest. Dietary fibre in the gut is like a tree trunk floating in a swimming pool: it may get wet, but it doesn't dissolve.'

The team also found that the abundance of these cellulose-decomposing gut bacteria varied across different human populations: They found that these bacteria were abundant in people who lived more than 1,000 years ago, modern hunter-gatherers, and rural people, but 'significantly rare' in modern urban populations.

It has been pointed out that modern people's diets are lacking in dietary fiber , and the decline in gut bacteria that break down dietary fiber may be due to the reduction in dietary fiber ingested. 'Our findings suggest a decline in these gut bacteria in the human gut, possibly due to the shift to a Westernized lifestyle,' the research team said.