Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. Genetic predisposition and general overnutrition are discussed as key factors in the development of NAFLD; however, alterations of intestinal microbiota composition and associated impairments of intestinal barrier function are thought to be critical in the onset and progression of NAFLD. In recent years, studies also suggest a pivotal role of bile acids and microbial bile acid metabolism as mediators of gut-liver-crosstalk subsequently affecting NAFLD initiation and progression. Soluble fibers like oat β-glucans bind bile acids and have been proposed to modulate intestinal microbiota composition thereby affecting metabolic parameters and liver health. Based on this background the main aim of the present transnational project is to reveal a causal relationship between specific diet-responsive microbial taxa and alterations of the bile acid pool as risk factor for initiation and progression of metabolic liver diseases. Herein, the effects of the soluble fibre oat β-glucan will be assessed. With this project the 5 partners aim to contribute to the understanding of the mechanisms involved in the development of NAFLD and to build the basis for new nutrition based therapeutic approaches.