Recent study Barley bread with positive influence on microbiome and glucose metabolism

The fiber-induced improvement in glucose metabolism is associated with an increase in Prevotella levels
The microbiome plays a significant role in health. Remarkable is the potential of certain diets or foods such as barley wholegrain to influence the composition of the bacterial intestinal inhabitants sustainable.

In a human study of the Swedish-Danish working group of the Universities of Lund and Copenhagen, the composition of the microbiome of healthy subjects after three days of consumption of barley whole grain bread compared to wheat white bread in the crossover method was examined. The overwhelming majority of respondents (hereafter referred to as responders) reacted with barley whole grain bread with improved glucose tolerance after the intervention phase. The postprandial glucose levels as well as the insulin increase in the serum were significantly lower than after the white bread phase.

Study on barley bread. Image: Lemonlord - fotolia

Only some of the subjects (non-responders) benefited only marginally from the consumption of barley bakery products in terms of glucose tolerance. In addition, the responders had a higher prevalence of Prevotella Bacteroides, associated with a significant increase in Prevotella bacteria, after the intervention period with barley bread than with non-responders. Prevotella copri in particular have been enriched in 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 gut that can split a wide range of fiber to produce health-promoting short-chain fatty acids (especially butyrate). They are therefore often and abundantly found in people who eat high fiber. A high proportion of Bacteroides is usually found in the intestine of mixed dieters. The heterogeneous bacterial group includes species with saccharolytic, but also proteolytic and lipolytic properties.

Furthermore, the human study tested the effect of the microbiota on glucose metabolism in germ-free mice. The administration of the microbiota from donors from the responder collective also improved the glucose metabolism in the animals, in conjunction with an increased number of microbes on Prevotella and an increase in liver glycogen. In germ-free mice receiving microbiota from the non-responder group, this effect could not be reproduced.

These data are an indication of a relevant role of Prevotella for improved glucose tolerance. An intervention with barley whole grain leads to a lower postprandial glucose increase via increased Prevotella growth, along with a reduced insulin secretion. There may also be a connection to an 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;