Grape seed extract is an extract from the tiny seeds of red grapes.
Grape seed extract is a source of oligomeric proanthocyanidin complexes (OPCs), some-times known as proanthocyanidins, which are one of the categories of flavonoids (see Flavonoids). Proanthocyanidins are polyphenol oligomers derived from flavan-3-ols and flavan-3,4-diols. Grape seed extract contains OPCs made up of dimers or trimers of catechin and epicatechin. Additional active ingredients in grape seed extract include essential fatty acids and tocopherols.
Grape seed is a potent antioxidant. Proantho-cyanidins are thought to:1
neutralise free radicals, including hydroxyl groups and lipid peroxides, blocking lipid peroxidation and stabilising cell membranes; inhibit the destruction of collagen by stabil-ising the activity of 1-antitrypsin, which in-hibits the activity of destructive enzymes such as elastin and hyaluronic acid (this is thought to prevent fluid exudation by allowing red blood cells to cross the capillaries);
inhibit the release of inflammatory media-tors, such as histamine and prostaglandins; and inhibit platelet aggregation.
In addition, they are thought to have antibacte-rial, antiviral and anticarcinogenic actions.
Grape seed extract is promoted as an anti-oxidant to prevent CHD and stroke, and to strengthen fragile capillaries and improve circulation to the extremities. It is promoted for the treatment of conditions associated with poor vascular function such as diabetes mellitus, varicose veins, impotence and tingling in the arms and legs. Anecdotally it has been reported to be useful for treating inflammatory condi-tions, varicose veins and cancer. It has also been suggested to be useful for helping to prevent macular degeneration and cataracts.
Oral administration of proanthocyanidins from grape seed extract reduced serum cholesterol in a high-cholesterol animal feed model.2 Specifi-cally, it prevented the increase of total and LDL cholesterol.
In a double-blind study, 71 patients with peripheral venous insufficiency received 300 mg daily OPCs from grape seed. A reduction in functional symptoms was observed in 75% of the treated patients compared to 41% of the patients given a placebo.3
In a double-blind clinical trial, a group of elderly patients with either spontaneous or drug-induced poor capillary resistance were treated with 100–150 mg OPCs from grape extract daily, or placebo. There was a signifi-cant improvement in capillary resistance in the treated group after approximately 2 weeks.4
A further trial evaluated the effect of a standardised formulation of a polyphenolic extract of grapes on LDL susceptibility to oxidation in a group of heavy smokers. This was a randomised, double-blind, crossover study involving 24 healthy male heavy smokers aged 50 years or over. Subjects were given two capsules (containing 75 mg of a grape procyanidin extract) twice daily for 4 weeks. This was followed by a washout period of 3 weeks and placebo for 4 weeks. Subjects did not show significant modification of total cholesterol, triglycerides, HDL or LDL cholesterol during grape seed extract treatment. However, among oxidative indices, the concentration of thiobar-bituric acid reactive substances was significantly reduced in subjects taking grape seed extract compared with placebo and basal values. The authors concluded that the antioxidant potential of grape seed extract polyphenols may prove effective as a model of oxidative stress (smoking). However, more investigational data are needed before use in wider clinical settings can be recommended.5
Grape seed extract is increasingly being investigated for other conditions. A double-blind RCT investigated the effect of grape seed extract in the treatment of seasonal allergic rhinitis. Patients with seasonal allergic rhinitis and skin prick test sensitivity to ragweed were randomised to 8 weeks’ treatment with grape seed extract 100 mg twice daily or placebo, which was begun before the ragweed pollen season. Over the period of the study, no significant differences were observed between active and placebo groups in rhinitis quality of life assessments, symptom diary scores or requirements for rescue antihistamine. No significant laboratory abnormalities were detected. Overall, this study showed no trends towards supporting the efficacy of grape seed extract in the treatment of seasonal allergic rhinitis.6
Grape seed extract has been shown to stimulate lipolysis in vitro and reduce food intake in rats. Leading on from these findings, a study has assessed the efficacy of grape seed extract with respect to energy intake and satiety. In a randomised, placebo-controlled, double-blind crossover study, 51 subjects (aged 18–65 years, body mass index 22–30) were given a grape seed supplement for 3 days, 30–60 min prior to ad libitum lunch and dinner in a university restaurant. In the total study population, no difference in 24-hour energy intake was found between grape seed extract and placebo. However, in a subgroup of subjects (n = 23) with an energy requirement ≥7.5 MJ/day, energy intake was reduced by 4% after grape seed compared to placebo. There were no significant differences in macronutrient composition, attitude towards eating, satiety, mood or tolerance. The authors concluded that these findings suggest that grape seed could be effective in reducing 24-hour energy intake in normal to overweight dietary unrestrained subjects and could therefore play a role in body weight management.7
No known contraindications, but based on the potential pharmacological activity of OPCs, i.e. that they may inhibit platelet aggregation, grape seed extract should be used with caution in patients with a history of bleeding or haemostatic disorders. It is probably wise to discontinue use 14 days before any surgery, including dental surgery.
Pregnancy and breast-feeding
No problems have been reported, but there have not been sufficient studies to guarantee the safety of grape seed extract in pregnancy and breast-feeding.
None reported. However, there are no long-term studies assessing the safety of grape seed extract.
None reported, but in theory bleeding tendency may be increased with anticoagulants, aspirin and anti-platelet drugs.
Grape seed extract is available in the form of tablets and capsules. Supplements should be standardised (and labelled) to contain 92–95% proanthocyanidins or OPCs.
The dose is not established, but doses of 100– 300 mg daily have been used in studies.
Preliminary evidence suggests that grape seed extract might lower lipid levels, improve symptoms of venous insufficiency and capillary resistance, reduce oxidative stress and play a role in body weight management. However, there are no well-controlled studies, and evidence for efficacy is promising but not yet robust.
Murray M, Pizzorono J. Procyanidolic oligomers. In: Murray M, Pizzorono J, eds. The Textbook of Natural Medicine, 2nd edn. London: Churchill Livingstone, 1999: 899–902.
Tebib K, Bessanicon P, Roaunet J. Dietary grape seed tannins affect lipoproteins, lipoprotein lipases and tissue lipids in rats fed hypercholesterolemic diets. J Nutr 1994; 124: 2451–2457.
Thebaut JF, Thebaut P, Vin F. Study of Endo-tolon in functional manifestations of peripheral venous insufficiency. Gaz Med France 1985; 92: 96–100.
Dartenuc JY, Marache P, Choussat H. Capillary resistance in geriatry. A study of a microan-gioprotector – Endotolon. Bord Med 1980; 13: 903–907.
Vigna GB, Costantini F, Aldini G, et al. Effect of standardized grape seed extract on low-density lipoprotein susceptibility to oxidation in heavy smokers. Metabolism 2003; 52: 1250–1257.
Bernstein DI, Bernstein CK, Deng C, et al. Evaluation of the clinical efficacy and safety of grapeseed extract in the treatment of fall seasonal allergic rhinitis: a pilot study. Ann Allergy Asthma Immunol 2002; 88: 272–278.
Vogels N, Nijs IM, Westerterp-Plantenga MS. The effect of grape-seed extract on 24 h energy intake in humans. Eur J Clin Nutr 2004; 58: 667–673.