What is Grape Seed Extract?
Grape seed extract is prepared from the seed of grapes. Grape seed extract contains a high concentration of proanthocyanidins, a class of polyphenol flavonoid complexes, and are known to possess the strongest antioxidant effect among polyphenols contained in red wine1, 2. Grape seed proanthocyanidins are potent antioxidants and free radical scavengers, which are more effective than either ascorbic acid or vitamin E13. Proanthocyanidins are classified according to their chain length, namely, monomeric, oligomeric and polymeric. Studies have revealed that oligomeric procyanidins (OPCs) are the most potent vasoacitve polyphenols in red wine.
Where Does Grape Seed Extract Come From?
As the name suggests, grape seed extract are derived from the processing of grape seeds. Red wine is one of the best known sources of grape seed extract, and is produced and harvested all around the world. However, the concentration of the OPC within red wine can vary according to the processing method and the region where it is grown3. For example, Wines from Nuoro and the Gers area in Southwest France have 2–4-fold more biological activity and OPC content than other wines from different geographical regions, such as Australia, Greece, Italy, Spain, South America, United States and Sardinia3.
Grape Seed Extract Benefits
Grape seed extracts are believed to possess a wide range of health beneficial properties, including protection against UV light-induced carcinogenesis, prevention of immune suppression, increasing the production of cytokines, stimulation of nonspecific immunity, activation of humoral immunity, and enhancement of cell-mediated immunity14-19.
Grape seed extract is most well-known for its beneficial effects on cardiovascular disease6. A classic example is the so-called French Paradox, which refers to the observation that subjects in France experience a relatively low incidence of coronary artery disease, despite high saturated fat consumption4. It has been suggested that France's high red wine (i.e grape seed) consumption is a primary factor in this trend5.
20 young Italian volunteers given 300mg of a specialised bioavailable grape seed extract (Leucoselect) for 5 days showed an increase in serum total antioxidant activity compared to placebo. When the same grape seed extract was given to a group of smokers for 4 weeks, they showed a reduction in a popular marker of oxidative damage7. Another double-blind trial involved type 2 diabetics (n=24) who received either the same grape seed extract 300 mg/day for four weeks or placebo. The grape seed extract significantly reduced urinary excretion of a free radical end-product (F2 lsoprostane) compared to placebo.
In addition to it beneficial cardiovascular properties, there is extensive literature documenting the different mechanisms by which grape seed extract can help prevent skin cancer8-10, however, most of this research has been done on animal and animal models. Grape seed extract has also been studied extensively for its antitumor and immunomodulatory effects13.
Negative Side Effects of Grape Seed Extracts
In a single-dose toxicity study on rodents, a proprietary product containing monomers and oligomers of proanthocyanidins administered (2000 mg/kg body weight) for 4 weeks showed excellent safety with no side effects12. Administration of the same product to 30 healthy volunteers at doses of 100 mg/day and 200 mg/day for 92 days showed good bioavailability and the liver and kidney functions as well as the hematological parameters remained within the normal ranges12. Therefore the likelihood of toxic or negative side effects from supplementation with grape seed extract are virtually nill.
Grape Seed Extract Recommended Dosages & Timing
Studies have used a wide range of grape seed extract doses from 50mg to 500mg per day.
Grape Seed Extract Supplements
Grape seed extract is most commonly sold in pill or tablet form, however, it is sometimes combined with other phytonutrients and antioxidants in a powder mix.
Stacking Grape Seed Extract
Grape seed is most commonly combined with other popular phytonutrient antioxidants such as green tea, silymarin and curcumin.
Grape Seed Extract Safety
Although human safety studies for grape seed extract are limited, no side effects have been reported in the literature so far. Grape seed extracts have been subjected to a series of toxicological tests that clearly document safety for use in various food and nutritional supplements11.
1. Corder R, et al. Oenology: Red wine procyanidins and vascular health. Nature. 2006;444:566.
2. Sánchez-Moreno C, et al. Anthocyanin and proanthocyanidin content in selected white and red winesOxygen radical absorbance capacity comparison with nontraditional wines obtained from highbush blueberry. J Agric Food Chem. 2003;51:4889–4896.
3. Corder R, et al. Oenology: Red wine procyanidins and vascular health. Nature. 2006;444:566.
4. Ferrières J. The French paradox: Lessons for other countries. Heart. 2004;90:107–111.
5. Renaud S, M. de Lorgeril. Wine, alcohol, platelets, and the French paradox for coronary heart disease. Lancet. 1992;339:1523–1526.
6. Feringa HH, et al. The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials. J Am Diet Assoc. 2011 Aug;111(8):1173-1181.
7. Vigna GB, et al. Effect of a standardized grape seed extract on low-density lipoprotein susceptibility to oxidation in heavy smokers. Metabolism. 2003;52(10):1250-1257.
8. Katiyar SK. Grape seed proanthocyanidines and skin cancer prevention: inhibition of oxidative stress and protection of immune system. Mol Nutr Food Res. 2008;52 Suppl 1:S71-6.
9. Sharma SD, Katiyar SK. Dietary grape seed proanthocyanidins inhibit UVB-induced cyclooxygenase-2 expression and other inflammatory mediators in UVB-exposed skin and skin tumors of SKH-1 hairless mice. Pharm Res. 2010;27(6):1092-1102.
10. Vaid M, Singh T, Katiyar SK. Grape seed proanthocyanidins inhibit melanoma cell invasiveness by reduction of PGE2 synthesis and reversal of epithelial-to-mesenchymal transition. PLoS One. 2011;6(6):e21539.
11. Ouédraogo M, et al. An overview of cancer chemopreventive potential and safety of proanthocyanidins. Nutr Cancer. 2011;63(8):1163-1173.
12. Fujii H, et al. Evaluation of the safety and toxicity of the oligomerized polyphenol Oligonol. Food Chem Toxicol. 2007;45:378–387.
13. Tong H, et al. Immunomodulatory and antitumor activities of grape seed proanthocyanidins. J Agric Food Chem. 2011;59:11543–1154.
14. Weber HA, et al. Comparison of proanthocyanidins in commercial antioxidants: Grape seed and pine bark extracts. J Agric Food Chem. 2007;55:148–156.
15. Mayer R, et al. Proanthocyanidins: target compounds as antibacterial agents. J Agric Food Chem. 2008;56:6959–6966.
16. Vaid M, et al. Proanthocyanidins inhibit UV-induced immunosuppression through IL-12-dependent stimulation of CD8+ effector T cells and inactivation of CD4+ T cells. Cancer Prev Res. 2011;4:238–247.
17. Seeram NP, et al. Berry fruits for cancer prevention: Current status and future prospects. J Agric Food Chem. 2008;56:630–635.
18. Li J, et al. Grape seed proanthocyanidins ameliorate Doxorubicin-induced cardiotoxicity. Am J Chin Med. 2010;38:569–584.
19. Hernandez-Jimenez A. Grape skin and seed proanthocyanidins from Monastrell x Syrah grapes. J Agric Food Chem. 2009;57:10798–10803.