A study by UC Davis indicates that grape seed extract shows potential as a way to lower blood pressure.

24 adults with metabolic syndrome (factors that increase that increase the risk of heart disease, such as high blood pressure) were divided up into three groups and followed for one month. One group was given a placebo, another 150 milligrams of grape seed extract and the final 300 milligrams of grape seed extract. In the end both groups receiving grape seed extract had an average drop in both systolic and diastolic blood pressure.

The study was small and the results should not be considered conclusive but may prompt further research.

Source:
“UC Davis Study Shows Grape Seed Extract May Be Effective In Reducing Blood Pressure”
UC Davis Health System: Newsroom. March 26, 2006. Can be viewed online at http://www.ucdmc.ucdavis.edu/newsroom/releases/archives/heartcenter/2006/grapeseed3-2006.html