Epidemiological studies are clear: diets in which plant foods provide the major portion of caloric intake, e.g. the Mediterranean and the Japanese diets, are associated with a reduced risk of certain degenerative diseases like cancer and atherosclerosis. Although fats and proteins in plants, as opposed to those of animal origin, are responsible to some extent for these protective effects, the contribution of other plant food components may also be relevant. In the past few years, research on polyphenols has remarkably expanded and is unveiling several biological activities of these compounds. Alas, the marketing departments of several industries are jumping ahead of solid scientific evidence; as a consequence, unsubstantiated claims are being made and whole foods or fortified, enriched, or enhanced foods are being created and sold. Science is beginning to corroborate some of these claims, but much more research is needed and several myths are to be disproven. In this mini-review we critically discuss the current limitations of polyphenol research and we contend that, in addition to their putative antioxidant action, several biochemical and physiological processes might be influenced by polyphenols.