“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.
Targeted restoration of such good bacteria may present a way to manage type 2 diabetes, the researchers write. Zhao tells STAT News that he’d like to experiment with microbiome changes to look for a way to reverse the course of the disease.