The fiber-induced improvement in glucose metabolism is associated with an increase in Prevotella
The microbiome plays an important role in health. The potential of certain diets or foods such as whole barley to have a lasting impact on the composition of the bacterial intestinal population is remarkable.
In a human study by the Swedish-Danish working group at the Universities of Lund and Copenhagen, the composition of the microbiome of healthy test subjects after three days of eating whole barley bread compared to wheat white bread was examined using the crossover method. The majority of the test persons (hereinafter referred to as responders) reacted with whole barley bread after the intervention phase with improved glucose tolerance. The postprandial glucose values and the increase in insulin in the serum were significantly lower than after the white bread phase.
Only a few of the test subjects (non-responders) benefited only marginally from the consumption of barley baked goods with regard to glucose tolerance. In addition, the Prevotella-Bacteroides ratio, combined with a significant increase in the Prevotella bacterial count, was higher after the intervention phase with barley bread than with the non-responders. Prevotella copri in particular has accumulated among the responders. In addition, an increased enzymatic potential for the fermentation of complex carbohydrates was observed in this collective.
Prevotella are among the microbes in the intestine that can break down a wide range of fiber to form health-promoting short-chain fatty acids (especially butyrate). They are therefore often and abundantly found in people who have a high fiber diet. A high proportion of Bacteroides can usually be found in the intestines of food lovers. The heterogeneous group of bacteria includes species with saccharolytic, but also proteolytic and lipolytic properties.
The human study also tested the effect of the microbiota on glucose metabolism in aseptic mice. The addition of the microbiota from donors from the responder collective also improved the glucose metabolism in the animals, combined with an increased number of Prevotella bacteria and an increase in liver glycogen. This effect could not be reproduced on aseptic mice that received microbiota from the non-responder group.
These data indicate the relevance of Prevotella for improved glucose tolerance. Intervention with whole barley leads to an increase in Prevotella growth and to a lower postprandial increase in glucose, accompanied by a reduced insulin release. There may also be a connection to increased hepatic glycogen storage and thus a reduced risk of diabetes.
About the study
Kovatcheva-Datchary et al. (2015): Dietary Fiber-Induced Improvement in Glucose Metabolism Is Associated with Increased Abundance of Prevotella. Cell metabolism 22, 971-982; December 1, 2015, Elsevier Verlag;