Considering the microcirculation, new diagnostic approaches such as Laser-Doppler Flow and peripheral arterial tonometry next to diagnostic approaches such as the venous occlusive plethysmography will be performed. Moreover, the circulating NO pool, markers of inflammation and of oxidative stress, the uremic toxin pcresol and the plasma levels of flavanols will be determined. The exams after month 1, 2, and 3 will be performed in the morning before intake of the cocoa drink. In order to examine potential sustained effects, an additional examination day will take place after 4 month (one month after stopping the flavanol-intake). It is expected that the flavanol-rich cocoa will improve vascular function, which is associated with an increase in the circulating NO-pool and a decrease in inflammatory markers and the marker for oxidative stress.