Grape seed extract

Grape seed extracts are industrial derivatives from whole grape seeds that have a great concentration of vitamin E, flavonoids, linoleic acid and phenolic procyanidins (also known as OPC or oligomeric procyanidins). The typical commercial opportunity of extracting grape seed constituents has been for chemicals known as polyphenols having antioxidant activity in vitro.

Possible health benefits
Human case reports and results from basic research provide preliminary evidence that grape seed extract may affect heart diseases such as hypertension, high levels of blood cholesterol, cancer, platelet aggregation or inflammation. Some of these effects have been demonstrated in vivo in animal models. According to the American Cancer Society, "there is very little reliable scientific evidence available at this time that drinking red wine, eating grapes, or following the grape diet can prevent or treat cancer in people".

A polyphenol contained in grape seeds is resveratrol, which is under study for its possible effect on cancer cell growth, proliferation or apoptosis, among other potential chemopreventive mechanisms.

Other preliminary research on disease models


 * skin and wounds – OPCs induced vascular endothelial growth factor and accelerated healing of injured skin in mice
 * teeth – seed phenolics may inhibit oral sugar metabolism and retard growth of certain bacteria that cause dental caries
 * bones – grape seed extracts enhanced bone density and strength in experimental animals
 * in vitro cancer studies – grape seed proanthocyanidins decreased tumor numbers and reduced the malignancy of papillomas
 * ultraviolet damage – dietary proanthocyanidins are under study for mechanisms against carcinogenesis and sunscreen protection
 * anti-viral effects
 * antibacterial properties
 * liver function
 * blood flow and fluid balance

There are 13 clinical trials (January, 2012) assessing potential effects of grape seed extracts on human diseases, such as breast cancer, blood estrogen levels in postmenopausal women, and coronary artery disease.

One clinical trial with adults having coronary disease or cardiac risk factors concluded that: "Four weeks of muscadine grape seed supplementation in subjects with increased cardiovascular risk did not produce a statistically significant increase in brachial flow-mediated vasodilation or a significant change in other biomarkers of inflammation, lipid peroxidation, or antioxidant capacity. However, the muscadine grape seed supplement did result in a significant increase in resting brachial diameter. The clinical significance of the effect on resting diameter is not yet established."

A meta-analysis of randomized controlled trials concluded that "grape seed extract appears to significantly lower systolic blood pressure and heart rate, with no effect on lipid or C-reactive protein levels."

The US National Center for Complementary and Alternative Medicine reported that oral administration of grape seed extract was well tolerated in people over 8 weeks. In one completed clinical trial, grape seed extract did not alleviate the hardening of breast tissue in female patients undergoing radiation therapy to treat breast cancer.

Dosage, precautions and interactions
Oral grape seed extract is used in capsules or tablets usually containing 50 mg or 100 mg. Insufficient scientific information is known, however, about how long-term use of grape seed extract might affect health or any disease.

Side-effects and cautions, other NCCAM advisories.
 * In general, grape seed extract is well tolerated when taken by mouth, although it is better tolerated when encapsulated, as its taste is bitter. It has been used safely for up to 8 weeks in clinical trials.
 * Side-effects most often include headache, a dry, itchy scalp, dizziness, or nausea
 * Interactions between grape seed extract and medicines or other supplements have not been carefully studied

Because of the possible action of proanthocyanidins on limiting platelet adhesion, grape seed extract may act as a blood-thinner, increasing clotting time.

Aromatase inhibitor
Grape seed extract is also an aromatase inhibitor in vitro, i.e. it may suppress the conversion of testosterone to estradiol.