Grape seed (Vitis vinifera) contains compounds called Proanthocyanidins. These substances neutralize free radicals, which are responsible for tissue damage and cell death in the body. Grape seed may also reduce the production of inflammatory substances in the body and inhibit the activation of platelets (“thinning” the blood). To date, small research studies suggest that grape seed may improve circulation, prevent atherosclerosis (clogging of the arteries), lower blood pressure, and lower cholesterol levels. Further research is needed to confirm these findings.
The most common side effects from grape seed include dry, itchy scalp; headache; dizziness and nausea. In theory, grape seed may increase the risk of bleeding, and should not be used by patients who take other blood thinning medications (Coumadin®, aspirin, heparin, Plavix®), or medications and supplements that could increase the risk of bleeding (ibuprofen, naproxen, ginko, garlic). Grape seed extract has been given in doses of 100 to 300 milligrams per day. The extract should not be used by people who are allergic to grapes.