Supplement analysis backed by scientific evidence · PT

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Moderate evidenceHeart & metabolic

Grape Seed Extract

Grape seed extract produces a small, fairly reproducible drop in systolic blood pressure and improves endothelial function. Its broader antioxidant, anti-ageing and lipid claims are not supported.

What the science says

  • Lowers systolic blood pressure Moderate evidence

    A meta-analysis of 16 randomised controlled trials found grape seed extract reduced systolic blood pressure by about 6.1 mmHg with no significant diastolic change; the effect was largest in younger participants and those with obesity or metabolic syndrome. A 2022 dose-response meta-analysis confirmed a modest systolic reduction, and found the effect did not increase with higher doses — more than about 300 mg/day added nothing.

  • Improves endothelial function Moderate evidence

    The same 2022 systematic review found grape seed extract significantly increased flow-mediated dilation, consistent with the proanthocyanidin mechanism shared with cocoa flavanols. Effect sizes are modest and trial durations short (2-16 weeks).

  • Improves lipid profile Limited evidence

    An earlier meta-analysis of randomised trials found no significant effect on LDL, HDL, triglycerides or C-reactive protein despite the blood pressure signal. Grape seed extract should not be sold or bought as a cholesterol treatment.

  • Reduces leg swelling and chronic venous insufficiency Limited evidence

    Small European trials report reduced lower-limb oedema and improved venous symptoms with 150-300 mg/day, and this is a traditional indication in France. Trials are old, small and often industry-sponsored; the evidence is suggestive rather than convincing.

Dosage & safety

Studied doseTrials used 100-800 mg/day of grape seed extract standardised to 80-95% oligomeric proanthocyanidins (OPCs), typically 150-300 mg/day in divided doses with food, for 4-16 weeks. Dose-response analysis suggests no additional blood pressure benefit above roughly 300 mg/day. Grape seed extract is distinct from resveratrol (mainly from grape skin) and from grape seed oil, which contains no meaningful OPCs.
SafetyGenerally well tolerated; headache, dry scalp, dizziness and nausea are the most common reports, and rates in trials were close to placebo. Proanthocyanidins have mild antiplatelet activity, so use caution with warfarin, DOACs, aspirin and clopidogrel, and stop at least 2 weeks before surgery. Grape seed extract may inhibit CYP enzymes and affect metabolism of some drugs; the clinical data are limited. Because it lowers blood pressure, combining with antihypertensives may cause additive hypotension. Avoid in people with grape allergy. Insufficient safety data in pregnancy, breastfeeding and children. Long-term data beyond 6 months are sparse.

Scientific references

Where to buy

California Gold Nutrition, French Grape Seed Extract, Vitaflavan®, 100 mg, 120 Veggie Capsules

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