A pilot study of 15 subjects will be conducted to confirm an acute effect of grape seed extract on endothelial function. We then will perform a a randomized, double blind, placebo controlled crossover study designed to investigate the benefit of grape seed extract/vitamin C treatment on endothelial function. Participants (n=40) will take a food supplement containing 450 mg of grape seed extract and 1500 mg of vitamin C or matching placebo for four weeks and then cross over to the alternative treatment (active supplement or placebo) for four weeks. We will examine endothelial function before and after each of the two treatment periods. The study will provide information about the vascular effects of these compounds.