Oxidative stress and inflammatory responses sustained for a long period of time cause many diseases. A proinflammatory cytokine, tumor necrosis factor α (TNF-α), plays a pivotal role in the pathogenesis of chronic and autoimmune diseases. The present review, supplemented by hitherto unpublished data of the authors and their coworkers, shows that the intake of polyphenols contained in natural sources, such as hydroxytyrosol, tyrosol, oleuropein (olives), naringin and hesperidin (Citrus fruits), resveratrol, procyanidins or oligomeric procyanidin (grapes or grape seed extracts), (-)-epigallocatechin gallate (green tea) and quercetin (grapes, green tea) etc., are able to modulate chronic inflammatory diseases, such as type 2 diabetes, rheumatoid arthritis, inflammatory bowel disease, and affect the formation and interaction of advanced glycation end products with their respective receptors. Furthermore, potent activities of fermented grape marc, prepared as a fine lyophilized powder from fresh skin and seeds of a Japanese grape strain (Koshu) and then fermented with Lactobacillus plantarum, are described. Finally, the bioavailability of representative polyphenols will be discussed.