Lignans are naturally-occurring compounds produced and accumulated in several edible and medicinal plants, which can be subdivided biosynthetically into lignans and neolignans. Once consumed, they can be transformed by gut microbiota into bioactive mammalian lignans. Such is the case of the conversion of the most studied and known dietary lignan, secoisolariciresinol diglucoside (SDG), into enterolactone (ENL) and enterodiol (END). Updated results comprising the action of these lignans (even other (neo)lignans) suggest that they exhibited positive effects on different diseases/disorders due to their free radical scavenging activity or capacity and capability to coordinate divalent transition metal ions to form complexes, in spite of a plausible, partially-registered prooxidant action. Therefore, some (neo)lignans are described as favorable chemical entities to human health, which their safety is also suitable since no detrimental effects are reported for the intake of some dietary lignans, exhibiting a more preventive than curative effect on diseases. Hence, in order to cover such an information about dietary (neo)lignans and their potential on human health as antioxidants, this document gathers the available information from chemical and biological point-of-views, including several topics such as sources, chemistry, bioavailability, antioxidant activity and action mechanisms, beneficial effects, and in vitro and animal/clinical studies.
