Once again a study found that a high fiber diet feeds beneficial gut microbes and causes changes in the gut microbe community (the microbiome). What's new in this study is that eating the high fiber diet had health benefits for people with type 2 diabetes - that it lowered their blood sugar levels (better blood glucose control), resulted in greater weight loss, and better lipid levels. And that when these gut microbes were transplanted into mice - they had similar health effects (better regulation of blood sugar). Which showed it was the microbes that caused the beneficial effects.
What foods are high-fiber foods? Fruits, vegetables, whole grains, nuts, seeds, and legumes (beans). [See Feeding Your Gut Microbes] From The Scientist:
A diet high in fiber can reshape the gut microbiome, helping people with type 2 diabetes stay healthy. A study published yesterday (March 8) in Science found that when patients with the condition ate a high-fiber diet, they had an abundance of microbial species that helped to reduce blood sugar and regulate weight compared with cohorts who ate a less fiber-rich diet.
“The study really gets at the mechanistic reasons of why these fiber-rich, plant-based diets may be helpful, especially in patients with type 2 diabetes,” Clare Lee, an endocrinologist at Johns Hopkins University who was not involved in the study, tells STAT News. “It’s an exciting step towards understanding potential mechanisms that can help us prevent and treat diabetes.”
In the study, microbiologist Liping Zhao of Rutgers University and his colleagues fed a group of 27 type 2 diabetes patients a diet of whole grains, traditional Chinese medicinal foods, and prebiotics for up to 86 days, while a group of 16 patients ate a similar diet with less fiber. All of the patients were treated with the diabetes drug acarbose, which helps transform starch into fiber.
For the first four weeks, hemoglobin A1c, a measure of blood sugar, fell in both groups. After day 28, however, those in the group that ate more fiber showed larger drops in blood sugar levels compared with the individuals who ate less fiber. At the end of the study, 89 percent of people on the high-fiber diet reached adequate blood sugar levels, while only 50 percent did while on the lower-fiber diet. Fecal analysis revealed that subjects on the high-fiber diet had drops in production of indole, hydrogen sulfide, and other metabolically detrimental compounds.
The team also transplanted the microbes of both sets of patients into germ-free mice. Animals that got the high-fiber-diet microbes had better regulation of blood sugar, while the mice that got the normal-diet microbes didn’t see such improvement. This experiment revealed that it was the gut microbes that were responsible for the changes in blood sugar and weight in the human subjects.