Grape seeds: powerful antioxidants provide protection

People all over the world have enjoyed grapes (Vitis vinifera) and grape products for centuries. Grapes are commonly grown in many regions of the World and are a popular fruit in many cultures. The unfermented juice of the grape is also very popular as a refreshing beverage, while many cultures utilize the fermented juice (wine) with their meals and social occasions.

There are more than 50 kinds of table grapes currently grown. Fresh table grapes come in three basic colors: green, red, and blueblack. Each variety possesses its own distinct color, flavor, and texture. Juice that is made from green grapes is called white grape juice. Grapes are most commonly available in late summer and during the fall season.

Grapes in History

In the nineteenth century John Harvey Kellogg used grapes to cure his patients with high blood pressure. Since the leaves of the grape plant have astringent properties, they have been used historically to treat varicose veins, diarrhea, and other ailments. Dried grapes, or raisins, have been a long-time favorite to sweeten cereal and bakery products, and are also used as a snack food.

Recently it was discovered that red grape juice contains compounds that inhibit blood clots. Because of this property grape juice has been recommended for people at risk for heart disease. The pharmacological properties of grape juice come from resveratrol and other flavonoids such as quercetin and catechin. The health-promoting substances in grape juice originate mostly from the skins of grapes, especially red grapes. These compounds also help fight cancer and possess anti-inflammatory properties.

Grape Seeds Are Active Too

The seeds of grapes have recently become very popular as a dietary supplement. The seeds contain high levels of proanthocyanidins, the major polyphenolics in the grapes. These flavonoid compounds can bind to each other, producing small polymers called oligomers.

Commercial preparations of grape seed extract are usually standardized on the basis of their proanthocyanidin content. These compounds are strong antioxidants, scavengers of free radicals, and they inhibit the oxidation of lipids. Grape seed extract was found to be a more effective antioxidant and free-radical scavenger than either vitamin C, vitamin E, or beta-carotene.

Grape seed extract reduces capillary permeability and fragility and is used for the treatment and prevention of vascular or circulatory disorders such as venous insufficiency, peripheral vascular disease, and varicose veins. Persons at risk for heart attack or stroke have also sought protection from cardiovascular disease by using grape seed extracts.

Grapes and grape products contain high levels of antioxidants that protect LDL cholesterol against oxidation, and protect the lining of the blood vessel walls. When fed to rabbits or mice, grape seed proanthocyanidin extract (GSPE) significantly improved cardiac function, attenuated the development of atherosclerotic lesions, and reduced cardiac tissue damage. In a human clinical trial GSPE supplements significantly reduced LDL oxidation in subjects with elevated cholesterol levels. Grape seed extract appears to be a therapeutic tool in promoting cardiovascular health.

Other Effects

A number of European trials have shown grape seed extract to effectively reduce circulatory problems and improve venus tone. One study also found that grape seed extract may be beneficial for improving night vision. Another suggests that grape seed extract may prevent cataract formation. Claims have been made that grape seed extract is beneficial in the treatment of diabetic retinopathy.

Animals treated with grape seed proanthocyanidins have a reduced incidence of skin tumors. Additional tests show that grape seed extract inhibits human breast cancer cells as well as lung and stomach cancer cells. Grape seed extract impairs angiogenesis, a major factor regulating tumor growth. Grape seed proanthocyanidins also have anti-inflammatory and antiviral activity.

Relation to Pycnogenol

The active ingredients of grape seed extract are similar to those found in the extract of the bark of the French maritime pine, Pinus pinaster. The pine bark extract is commercially marketed as Pycnogenol. Cranberries, blueberries, almonds, peanuts, cocoa, and some other nuts and berries also contain the health-promoting proanthocyanidins.

Usage and Safety

While reliable information is fairly scarce, grape seed extract appears to be safe to use. It has a low toxicity, and side effects have not been reported. It is not recommended for use during pregnancy or during breast feeding. No interactions with food or other herbal supplements are known at this time. The therapeutic effectiveness of grape seed extracts may vary considerably, since the absorption of proanthocyanidins appears to vary Widely among subjects.

For general health purposes the typical dosage of grape seed extract is about 50 to 200 miligrams a day, providing a daily dose of up to 150 miligrams of proanthocyanidins. The extract is available in the form of either capsules or tablets. Commercial grape seed products are often labeled as containing OPCs--oligomeric proanthocyanidins.

Remember:

Herbal products and dietary supplements can have pharmacological effects, may produce adverse reactions in some people, and could interact with over-the-counter and prescription medications you may take. Discuss with your physician your decision to use any herbal product. Anything mentioned in this article is not intended to diagnose, prescribe, or treat any ailment.

Winston J. Craig, Ph.D., R.D., is a professor of nutrition at Andrews University, Berrien Springs, Michigan.

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