The effect and selectivity of dietary fibers on intestinal bacteria is now demonstrated. In a series of controlled trials, researchers from DTU and Washington University School of Medicine, St. Louis (USA), show that plant-based fibers affect the microbiome of mice that host a human microbiota and as well as that of humans.
In experiments conducted with fibers from the peel of peas and oranges, the researchers show that the fibers affect the abundance of certain intestinal bacteria and specific carbohydrate-processing enzymes as well as the plasma protein profile of the host.
Image credit: Free-Photos via Pixabay, CC0 Public Domain
“We can measure that dietary fibers have an influence on the our gut microbiome. Depending on what fiber we add to the diet, we can see that it affects specific families of enzymes that break down complex carbohydrates such as starch, pectin, xylan and xyloglucan. And at the same time we can see through analysis of blood samples from the subjects, that plant fibers induce changes in their plasma protein profile including on markers usually associated with obesity,” says Professor Bernard Henrissat from DTU Bioengineering.
Examination of 30 fibers
The dietary fiber trial study is published in the acclaimed journal Nature. The first phase of the experiment was performed in mice colonized by the digestive microbiome of patients suffering from obesity or who were overweight. With this mouse model the researchers investigated the effect of different types of dietary fibers on the microbiome. After the mice were colonized with the intestinal bacteria from the human donors, they were given a standardized diet, and the diet was later supplemented with selected plant fibers, after which the researchers investigated the effect of on the mice's intestinal bacteria and on the carbohydrate-digesting enzymes that they produced. In total, the researchers examined the effect of fibers from a total of 30 different types of plants.
Based on the results of the mouse experiments, the researchers developed snacks with fiber from the peel of peas and oranges that had been shown to be particularly good at stimulating different types of carbohydrate-digesting enzymes in the mouse experiments. The snacks were then used in a human trial with 12 genetically identical twins to minimize interpersonal variations. During two trial periods, each of which stretched over 49 days, the twins received a normal western diet high in fat and low in fiber, and after one to two weeks, they received an additional fiber snack as a supplement to their diet.
Identification with machine-learning
The analyses of the variations in intestinal bacteria and their encoded enzymes, which were conducted with techniques inspired from signal processing and machine-learning, allowed to identify several families of carbohydrate-digesting enzymes whose abundance was affected by the addition of the fibers to the diet. The results on the mice allowed to select the best performing fibers for the human trials. First the researchers found out that in humans too the fibers had a selective effect on the abundance of several families of carbohydrate-digesting enzymes. Then a complete proteomics analysis of the plasma proteins of the patients was performed using mass spectrometry, which is a way to determine the mass of molecules. Using these technologies, the researchers could document how the different types of fibers affect the abundance of bacteria and of carbohydrate-active enzymes in the subjects' stools and the plasma protein profile in the subject’s blood.
Open doors to dietary interventions
“The subjects did not lose weight due to the diet during the three weeks they were fed plant fibers in the experiment as this was not the subject of the experiment –the subjects had no restrictions on the amount of food they ate. Instead we wanted to observe whether the snacks could elicit changes in the chemical processes, and in a different profile of carbohydrate-active enzymes of the microbiota. Our study shows that indeed it is possible to use dietary supplements for intervention on both the digestive microbiota and on the health parameters of the patients. This opens the door to future dietary interventions in multiple pathologies” says Bernard Henrissat.
Source: DTU