**5. Polyphenols and prostate cancer**

Dietary polyphenols (PPs) have gained much traction over the last years for their potential as reliable chemopreventive and antitumor agents. This was partly due to their presence in a range of foods and beverages commonly consumed by humans including fruits, vegetables, coffee, tea, and wine [67, 68]. In terms of chemical structure, polyphenols are compounds with at least one aromatic ring with one or more hydroxyl group attached [68]. They are grouped into four different classes based on their chemical structure and orientation of the number of phenolic rings bound to each other. These four classes are as follows: phenolic acids, flavonoids, stilbenes, and curcuminoids [67]. Phenolic acids are found in all plant materials and account for 30% of all polyphenols consumed. They are found mainly in acidictasting fruits, coffee, and green tea. As the most abundant group of polyphenols, flavonoids account for 60% of all polyphenols consumed by humans. Good sources of flavonoids include berries, black tea, all citrus fruits, and wine. Together, phenolic acids and flavonoids are the most abundant dietary polyphenols consumed by humans and, consequently, are the most studied with regard to their health benefits to conditions including cancer.
