The flavanol-dosis that is necessary to affect vascular function will be assessed as described above. At the beginning of the study, after the first intake of the cocoa (in order to identify nonresponders) and monthly for a period of three months the vascular function will be assessed applying innovative imaging techniques to the brachial artery to assess endothelium-dependent regulation of physicomechanical properties and vascular tone and thus blood flow at the level of the macrocirculation. In parallel new techniques will be applied to assess perfusion at the level of the microcirculation. In particular, measurement of flow-mediated dilation, intima-media-thickness,compliance and stiffness indices will be performed in the macrocirculation of the brachial artery.