Functional foods are foods with a physiological function for body in addition to their role in nutrition and satiation. With the increase in immune and emerging diseases, related to unhealthy nutrition, as it is strongly linked to digestive system diseases, which result in most other diseases. Therefore, it is incumbent upon us, each in his specialization, to point out the critical importance of functional nutrition in general, and fermented foods as one of the broadest sectors of functional foods especially; as microbial metabolism products after fermentation contribute to the production of many chemical compounds with important physiological functions.

Using fermented foods has been known since ancient civilizations, folklore and some festive seasons, either because of its distinctive flavor or to increase the duration of preservation, or for its health importance, and this is in both animal and vegetable sources, and for being a special food as a religious custom or for vegetarians.

Conclusion: This article aims to point out the importance of fermented foods and mention some of their sensitive functions, which may contribute to the advancement of humanity and take its hand to return to nature and a healthy life style.

Keywords: Fermented foods; brain-gut axis; immunity-enhancing; anti-microbial; anti-oxidants; anti-inflammatory and traditional folklore.