Grape Seed Extract

Claims, Benefits: Treats everything from cancer, arthritis, and diabetes to varicose veins and macular degeneration.

Bottom Line: There's no evidence that it is effective against any of these disorders. It does, however, contain interesting flavonoids, which are being seriously studied and may have a bright future. Meanwhile, consume flavonoid-rich foods instead.

Full Article, Wellness Letter, June 1999:

Ask the Experts

Q: What's in grape seed extract? And what is it good for?

A: Marketers of this dietary supplement claim that it alleviates a host of problems and diseases, from cancer, arthritis, and diabetes to varicose veins and macular degeneration. There's no evidence it is effective against any of these disorders. It does, however, contain interesting compounds, which are being seriously studied and may have a bright future as more knowledge emerges.

What's special about grape seed extract is its high level of certain flavonoids, notably proanthocyanidins, also called procyanidins. (For more on flavonoids and other phytochemicals, see our April 1999 issue.) These compounds are also found in green tea, red wine, and pine bark (the last is marketed as pycnogenol.

Test tube and animal studies have found that the special flavonoids in grape seed extract are potent antioxidants. There's very preliminary evidence that these compounds may help maintain connective tissue (as in tendons, ligaments, and cartilage) and affect vascular disorders.

However, scientists still understand little about the exact effects of these (and other) plant chemicals in the human body. They don't know which grape species should be used or what doses taken. We cannot recommend that you take grape seed extract at this point. We can wholeheartedly recommend that you eat grapes, berries, and other fruits and vegetables rich in flavonoids and other phytochemicals. And drink tea, wine (in moderation), and grape juice, if you like them.

UC Berkeley Wellness Letter, June 1999