High consumption of fruit and vegetables is associated to a better health, and to lower incidence of cardiovascular diseases, diabetes, certain cancers, and several other age-related degenerative disorders. These health benefits could be associated to a group of phytochemicals present in edible plants and derived foods and beverages, generically termed polyphenols. The distribution of polyphenols in plants is complex and their concentrations and proportions in each plant are not just genetically determined but affected by the breed of the plant, environmental factors, and the different processing steps. The general hypothesis is that the health benefits are surrogate to the antioxidant actions of the polyphenols based on a set of chemical features shared by these compounds. However, direct antioxidant effects require tissue concentrations of polyphenols reached only in certain tissues. Thus, additional actions compatible with actual polyphenol levels are under intensive research. Nitric oxide concentration determinants are discussed as an antihypertensive mechanism with multiple steps susceptible to be modulated by certain flavonoids.