Seeds of the fruit of the vine, once discarded as waste after the juice was pressed out for wine, have become the source of a popular dietary supplement.
Grapes were first cultivated near the Caspian Sea, and their use as food and drink had spread throughout the Mediterranean world before the Bible was written.
The ancient Greeks believed that wine had wonderful health benefits, and modern science has confirmed that wine has many useful properties. While the benefits of wine may be tarnished by the devastation associated with alcohol abuse, the positive aspects of grape seeds have no such liability.
The French have published much of the research on grape seed extract, but ironically grape seeds were a “second choice.” Manufacturers turned to using grape seeds only when peanut skins became unavailable.
Most of the high-quality grape seed extract sold in the United States is manufactured by an Italian company called Indena.
The oil pressed from grape seeds contains a number of essential fatty acids and is rich in vitamin E compounds.
The most interesting constituents of grape seeds are the polyphenols (catechins). These tannin compounds, also called procyanidins, leucoanthocyanins, pycnogenols, or oligomeric proanthocyanidins (OPC), are powerful antioxidants. Commercial extracts are generally standardized for OPC content.
Grape leaves and presumably seeds also contain flavonoids, and the skin and seeds are the source of several recently identified compounds known as 5-nucleotidase inhibitors.
Grape seed oil can be used for cooking. It has an unobtrusive flavor and a high smoking point and is rich in omega-6 fatty acids.
Grape seed extract is used in Europe to improve circulation. It prevents oxidation of blood fats and inhibits enzymes that break down the proteins that make up blood vessels.
Grape seed is believed to benefit cardiac and cerebral circulation. In animals it reduces capillary permeability and presumably has similar activity in humans.
Capillaries may be fragile due to diabetes or other disorders. In four small studies, grape seed extract was better than placebo at improving peripheral circulation as well, resulting in less pain and swelling, fewer nighttime cramps, and less numbness and tingling.
Studies have shown that grape seed extract may slow macular degeneration, improve vision stressed by computer screens or glare, and reduce myopia. Although further research is needed, the results have been promising.
In test tube research grape seed polyphenols stop the growth of Streptococcus mutans, a bacteria that causes tooth decay. They also slow the conversion of sucrose (table sugar) into glucan, and as a consequence of both these actions, grape seed may have a role in maintaining dental health.
Another potential benefit of grape seed extract is anti-inflammatory activity.
Usual dose for general health maintenance ranges from 50 to 100 mg daily.
To treat illness, doses from 150 to 300 mg per day are recommended.
No special precautions have been noted.
Animal studies indicate that some of the polyphenols are toxic to the liver; other constituents appear to be hepatoprotective, preventing liver damage due to carbon tetrachloride in mice. There are no data that permit evaluation of these effects in humans.
Grape seed extract is fairly high in tannin. It might be prudent not to take this herb at the same time as iron supplements, although no interactions have been documented.