For thousands of years, locally and internationally, a particular family of foods exists in our diet: the fermented foods. These ''living'' foods, shaped by microorganisms , have microbiological, biochemical and physicochemical characteristics that are very different from the raw material they are made of. Consequently, they have been granted with many nutritional and health benefits, although the studies that have been conducted on these foods are not sufficient and can hardly be generalised (i.e.: to a generic effect). However, in the current context of expectations of sustainability and naturalness, it is clear that these foods could have a central role to play in our food systems. The issue concerning their health value, especially in the light of new knowledge on the gut microbiota, needs to be clarified in order to consider the place of fermented foods in dietary recommendations.