Grape seed extract is used for conditions related to the heart and blood vessels, such as atherosclerosis, hypertension, hypercholesterolemia, and peripheral vascular disease. Other reasons for using grape seed extract include complications related to diabetes, such as peripheral neuropathy and retinopathy; vision problems, such as macular degeneration (which can cause blindness); and edema after an injury or surgery. It's also used for cancer prevention and wound healing.

What the science says

* Studies have shown that grapes counteract free radicals, which are highly reactive molecules that can damage cell function.

* Grape seed extract has shown some beneficial antioxidant effects in preliminary clinical trials. However, few trials have looked at specific diseases or conditions, and little scientific evidence is available.

* A study funded by the National Cancer Institute found that grape seed extract didn't reduce radiation-induced skin fibrosis after breast cancer treatment.

Current research

* The National Cancer Institute is funding studies evaluating whether grape seed extract helps prevent breast and prostate cancers.

* The National Center for Complementary and Alternative Medicine is also studying whether the action of grape seed extract and its components may benefit the heart or protect the brain.

Tolerance, adverse reactions, and cautions

* Available in capsule and tablet forms, grape seed extract is generally well tolerated when taken by mouth. It's been used safely for up to 8 weeks in clinical trials.

* Common adverse reactions include headache; a dry, itchy scalp; dizziness; and nausea.

* The interactions between grape seed extract and drugs or other supplements haven't been carefully studied.

Source: National Center for Complementary and Alternative Medicine, http://nccam.nih.gov/health/grapeseed/.