How fibre-rich diet prevents diabetes and obesity

It has been known for year that a fibre-rich diet protects the organism against obesity and diabetes, and not a French-Swedish team of researchers has succeeded in elucidating this mechanism, which involves the intestinal flora and the ability of the intestine to produce glucose between meals.

The study also clarified the role of the intestine and its associated microorganisms in maintaining glycaemia. They will give rise to new dietary recommendations to prevent diabetes and obesity.

Most sweet fruit and many vegetables such as salsify, cabbage or beans are rich in so-called fermentable fibres. Such fibers cannot be digested directly by the intestine but are instead fermented by intestinal bacteria into short-chain fatty acids such as propionate and butyrate, which can in fact be assimilated by our bodies.

The protective effect of these fibers is well known to researchers: animals fed a fiber-rich diet become less fat and are less likely to develop diabetes than animals fed a fiber-free diet. Nevertheless, the mechanism behind this effect has until now remained a mystery.

The team headed by Gilles Mithieux, CNRS researcher in the "Nutrition et Cerveau" unit (Inserm / Universite Claude Bernard Lyon 1), wondered whether this mechanism could be linked to the capacity of the intestine to produce glucose.

The researchers subjected rats and mice to diets enriched with fermentable fibers, or with propionate or butyrate and observed a strong induction of the expression of genes and enzymes responsible for the synthesis of glucose in the intestine.

They showed that the intestine of these animals used propionate as precursor to increase the production of glucose. Mice fed a fat- and sugar-rich diet, but supplemented with fibers, became less fat than control mice and were also protected against the development of diabetes thanks to significantly increased sensitivity to insulin.

The work sheds light on the role of the intestinal flora which, by fermenting dietary fiber, provides the intestine with precursors to produce glucose and also demonstrates the importance of the intestine in the regulation of glucose in the body.

The study is published in the journal Cell.