Integrated multi-scale strategies to investigate nutritional compounds and their effect on the gut microbiota

A complex relationship occurs in the intestine between the gut microbiota, diet, and host. The modulation of the gut microbiota composition and activity is a target for health-promoting strategies and possible novel therapeutic approaches. Different in vitro and in vivo strategies have been applied to elucidate mechanisms or functions of dietary compounds on the gut microbiota, health, and physiology of human. Recent research has shown the potential of combining in vitro models and in vivo investigations within a coherent strategy. This review highlights recent developments and limits of in vitro gut fermentation and cellular models, gnotobiotic animals, and human trials. Combination of experimental scales is illustrated for resolving the complex mechanisms of dietary iron on gut microbiota, health, and infections.