Theapplication of the hygiene hypothesis to the emerging knowledge on the humanmicrobiota can also be carried out by studying foods, which are not only asource of possible pathogens. Especially in their fermented forms foods arealso able to pro-vide us with beneficial microorganisms and their products. Thesemicroorganisms are related to the multitude of probiotics for which healthyeffects are postulated.

Startingfrom the microbiota hypothesis, which describes the relationship between the diseasesof civilization and the modification of the intestinal microbiota, the originof the fermentation of food and the possible adaptation of humans to these is analyzed. During the Neolithic,we have not only had access to new sources of food, but also to new forms ofpreparation, fermentation being one of them, which on the other hand is at risk of falling into disuse. Thepossible pre- and probiotic effects of fermented foods are also analyzed.

Whilethe new food technologies open the doors to the design of probiotics withspecific effects on health, we should not leave aside the studies on thepossible healthiness of traditionally fermented foods.