Plant phenolic substances and phenolic substances in food have continually been a subject of scientific research. Thanks to this research effort, knowledge concerning the chemical structure and occurrence of these compounds in food has become more accurate. Properties and effects other than the antioxidative ones have been confirmed in relation to the phenolics. Some of their biological activities have been discovered (for instance the blocking, initiation and progression processes in carcinogenesis). There is a chance to evalute them in cancer research and to apply them in the therapy and prevention of this disease. The traditional epidemiological research evaluating these natural substances as a part of diet continues but the shift to interventional studies aimed at the recognition of the art and mechanisms of phenolic biological action is obvious.
Regarding digestion and the metabolic pathway, plant phenolics are partially deglycosylated in the small intestine, and a passive or active transport into the bloodstream follows. The enzymatic scission of the phenolic molecules may proceed and, after the conjugation reactions, the catabolites are excreted in urine or in feces. A portion of the phenolics is catabolized in the colon by the action of bacterial microflora. In human plasma the maximum concentration of phenol substances reaches about 1 μmol/l after an usual dietary uptake of fruit, vegetables, legumes or cereals.
Plant polyphenols contribute essentially to the health benefit of fruit and vegetables, giving them the qualitative character to be termed "functional food". An increased consumption of that food is recommended and the addition of these compounds to the food in the near future is supposed.

Keywords: Polyphenols; Chemoprotective substances; Disease prevention; Foods of plant origine