Most participants had prehypertension; the others had normal blood pressure. Prehypertension falls between normal and high blood pressure.
Participants were split into three groups. One group got a fake (placebo) treatment. Another group took 150 milligrams per day of grape seed extract. The third group took 300 milligrams daily of the same grape seed extract.
Four weeks later, blood pressure had dropped for those taking grape seed extract. Blood pressure didn't change in the placebo group.
The findings were presented in Atlanta at the American Chemical Society's National Meeting & Exposition.
Blood Pressure Effects
The two extract doses were "equally efficient in lowering the blood pressure," researcher C. Tissa Kappagoda, MD, PhD, tells WebMD. Kappagoda specializes in cardiovascular medicine at the University of California at Davis.
Systolic blood pressure (the top number in a blood pressure reading) dropped 12 points, on average. Diastolic blood pressure (the bottom number in a blood pressure reading) dropped an average of 8 points, Kappagoda says.
The blood pressure changes were seen "across the board," not just in people with prehypertension, says Kappagoda. He notes that his team had already done preliminary work on people with normal blood pressure and found no dangerous drop in blood pressure with grape seed extract.
Kappagoda and colleagues had previously found that grape seed extract might help dilate blood vessels. "Because of that, we thought it had potential as a blood-pressure-lowering agent," Kappagoda says.
Talk to Doctor First
Grape seed extract isn't marketed with any health claims, Kappagoda points out.
He says people who are thinking about taking grape seed extract should consult their doctors. Kappagoda also says he "wouldn't want to recommend" that anyone stop taking medicine for high blood pressure in favor of grape seed extract.
"But on the other hand, if their physicians have said, 'You know, you're kind of borderline,' and so on, then there may be some place for this after consulting their physician," Kappagoda says, pointing out that doctors usually recommend lifestyle change -- not prescription drugs -- to treat prehypertension.
The study was funded by the extract's maker, Polyphenolics Inc.