According to the report produced in 2014 by the World Health Organization (WHO), the chronic non-concommunicable diseases (NCDs), i.e. the so-called diseases of civilization that include inter alia cardiovascular diseases, chronic respiratory diseases, cancer or type 2 diabetes, are now an immediate cause of more than 50 % of all premature deaths worldwide. The research carried out over the past 20 years proved that the diet was an essential factor to influence the risk of those diseases. On the other hand the growing consumer knowledge of chemopreventive properties of certain food ingredients, in particular of those derived from plants, made it possible to use some edible plants to prevent chronic diseases. Health promoting properties of those foods are mostly associated with the presence of antioxidants that may affect many essential biological mechanisms of critical importance for the proper functioning of human body. In numerous research studies strong physiological effects of, among others, bioactive plant phenols were demonstrated. Those observations have become commercialized in the form of mass production of dietary supplements enriched with the substances referred to as antioxidants, although their chemical properties did not always justified the use of this term. In the epidemiological studies it was proved that the expectations of entrepreneurs were not fully reasoned. It turned out that the isolated bioactive phytochemicals might not be as effective as chemopreventive factors as were the fruits or vegetables containing them. In the paper it was attempted to critically assess the reasons of this situation.