Eat fiber so that bacteria don't eat you
Anna Stavina, XX2 century
Microbiota plays a crucial role in maintaining the health of the human body. A new study has revealed what happens when bacteria in our gut don't get enough of the fiber they need.
There are at least 1,000 known bacterial species in the gut microbiota, and the total number of their genes is approaching 3 million. A third of the microorganisms living in the intestine are common to all people, the remaining two–thirds are a unique set for each person.
Microbiota is important for health because it contributes to the immune system, protecting us from harmful microorganisms. Bacteria living in the gastrointestinal tract are involved in digestion, breaking down foods that our stomach and small intestine would not otherwise cope with. Also, some vitamins are produced in the microbiota.
Doctors and nutrition experts often talk about the role of fiber in a healthy diet. And a new study has shown exactly what happens in the gastrointestinal tract if we don't get enough dietary fiber.
Study of microbiota changes in mice
The study was conducted by a group of scientists from different countries. The work was led by Eric Martens, associate professor of microbiology at the University of Michigan Medical School and Mahesh Desai from the Luxembourg Institute of Health.
Mice born and raised without their own microbiota were bred for the study. Then the animals were planted with 14 types of bacteria commonly found in the human intestine.
The "genetic signature" of these bacteria was known to scientists, which made it possible to track the changes that occurred with each species over time. The work was carried out in a sterile laboratory using genetic methods, thanks to which the researchers were able to determine exactly which types of bacteria persisted and continued to work in the intestine after the mouse began to receive certain nutrition.
Scientists studied the effect on the intestines of mice of diets with different fiber content, as well as a diet that did not contain fiber at all. In particular, nutrition was used, in which fiber was 15%. It was made from plants that had undergone minimal processing. Also, as part of the experiment, some mice received food rich in prebiotic fiber – a purified form of soluble fiber, similar to that used in ready-made food and dietary supplements.
Gut bacteria really need Fiber
According to the results of a study published in the journal Cell (Desai et al., A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility), an artificially introduced infection failed to infect mice fed with 15% fiber content. The mucus layer in their intestines turned out to be too thick, which protected the animals from the disease.
But when scientists began to feed these mice with food that lacked fiber, the bacteria began to eat the protective mucus. Just a few days on the new diet was enough for the microorganisms to penetrate the intestinal wall.
A drawing from the University of Michigan High-fiber diet press release keeps gut microbes
from eating the colon’s lining, protects against infection, animal study shows – VM
The microorganisms that make up the gut microbiota feed on fiber. Without receiving it, they begin to eat the intestines themselves, making it vulnerable to infections.
A diet that contained prebiotic fiber showed the same results as a diet that did not contain fiber at all. Against the background of such a diet, the mucus layer began to break down under the influence of microorganisms.
"The lesson we learned from observing the interaction of fiber, bacteria and gut defense systems is that if you don't feed your microorganisms, they will start eating you," said Eric Martens.
The researchers were also able to determine which digestive enzymes were produced by the bacteria of the mouse microbiota. In total, about 1,600 different enzymes that break down carbohydrates were found – something similar is observed in the human gastrointestinal tract.
The lack of fiber increased the production of enzymes that break down mucus.
Scientists were also able to study images of goblet-shaped intestinal cells responsible for the production of mucus. They found that the mucus layer thinned as the mouse received less fiber.
Normally, mucus is produced and split at the same rate. But on a low-fiber diet, the rate of mucus breakdown significantly exceeded the rate of its production.
By studying the intestinal tissues of infected mice, the scientists found foci of inflammation around the places where the mucus layer had thinned. Inflammation was also observed in infected mice that received fiber-rich food, but the area of the foci in this case was much smaller.
Future research on various diets
In the future, Martens and Desai hope to study the effect of taking combinations of various prebiotics for a long time. They also plan to study the effects on the body of a diet in which natural fiber is supplied intermittently.
In addition, the researchers would like to find biomarkers that allow us to assess the state of the mucus layer in the human gastrointestinal tract and determine the number of bacteria that corrode this layer. Another possible goal of future work is to study the effect of a fiber–deficient diet on the course of chronic diseases, for example, inflammatory bowel diseases.
"Although this work was carried out on mice, it contains important information for humans. In fact, the study repeated what doctors and nutrition experts have been telling us for decades: eat more fiber from various natural sources.
Your diet directly affects your microbiota. It can affect the condition of the mucus layer protecting the intestines, and the likelihood of developing diseases. The only question left open is whether we can get rid of the fiber deficiency caused by our dietary habits with the help of something more refined and edible than a head of broccoli," said Martens.
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