A likely guess would be grape juice, since researchers have long proven the heart health benefits of red wine but a study published January 28 in the Journal of Agriculture and Food Chemistry shows drinking cranberry juice can lower blood pressure.
Roger Corder, BSc, MSc, PhD, MRPharmS, author of T he Red Wine Diet and professor at Queen Mary University of London, identified oligomeric procyanidins, which prevent blood vessel constriction the leads to heart disease, in cranberries.
Corder explained, "...cranberry juice is a very promising alcohol-free alternative. We have now identified oligomeric procyanidins as the specific compound in cranberries that can boost the health of blood vessels, helping to prevent blood vessel constriction - a leading cause of high blood pressure".
Full study, Regulation of Vascular Endothelial Function by Procyanidin-Rich Foods and Beverages: http://pubs.acs.org/doi/abs/10.1021/jf9031876?prevSearch=%255Bauthor%253A%2BRoger%2BCorder%2B%255D&searchHistoryKey=