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.
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
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 Integrative Health 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.
