Grape Seed Extract
Vitis vinifera
TL;DR
Grape seed extract, standardised to oligomeric proanthocyanidins, lowers blood pressure modestly in meta-analyses — around 6 mmHg systolic in younger and metabolically at-risk groups — and has a smaller literature on chronic venous insufficiency and oedema.
Ideal For
- Mildly elevated blood pressure, particularly with metabolic syndrome
- Chronic venous insufficiency, leg heaviness and oedema
- Capillary fragility and easy bruising
- Endothelial function support alongside other cardiovascular measures
Avoid If
- Taking warfarin or antiplatelet therapy
- Within two weeks of surgery
- Pregnancy or breastfeeding
- Expecting meaningful benefit from generic antioxidant claims
Frequently Asked Questions
Overview
Grape seed extract is a reasonable, unglamorous vascular supplement whose evidence is better than its reputation and weaker than its marketing. Meta-analyses of randomised trials report reductions in systolic blood pressure of roughly 6 mmHg and diastolic around 3 mmHg, with the effect concentrated in younger participants and in those with metabolic syndrome or obesity rather than in older, established hypertensive populations. Endothelial function measured by flow-mediated dilation improves in several trials, which is a coherent mechanistic corroboration. Beyond blood pressure, the more traditional European use is in chronic venous insufficiency and capillary fragility, where proanthocyanidins appear to reduce leg oedema and heaviness — an application shared with horse chestnut and pine bark extract, all of which work through similar collagen-stabilising and capillary-sealing mechanisms. The antioxidant marketing is where things get overstated: proanthocyanidins have impressive test-tube antioxidant capacity and modest bioavailability, and generic antioxidant claims should carry little weight. Standardisation to at least 90-95% proanthocyanidins is the practical purchasing criterion.
How It Works
- Increases endothelial nitric oxide synthase and protects nitric oxide
- Inhibits collagenase and elastase, stabilising capillary walls
- Reduces capillary permeability, easing oedema
- Mild ACE inhibition and reduced LDL oxidation
Quick Facts
- Roughly 6 mmHg systolic reduction in pooled trials
- Effect is larger in younger and metabolically at-risk groups
- Also used for venous insufficiency and leg oedema
- Standardise to 90-95% proanthocyanidins
Benefits & Outcomes
Venous Return
Grape seed proanthocyanidins show modest symptomatic benefit in venous insufficiency.
Capillary Density
Grape seed proanthocyanidins may support capillary integrity, with the clearest data in chronic venous insufficiency rather than performance.
Supporting Research11 studies
Grape seed extract hepatotoxicity: LiverTox clinical and research information review
LiverTox
Grape seed extract has not been convincingly linked to clinically apparent liver injury, and trial safety data show good tolerability at usual doses.
The effect of grape seed extract supplementation on flow-mediated dilation, blood pressure, and heart rate: a systematic review and meta-analysis with dose-response analysis
Foshati S, Nouripour F, Sadeghi E +1 more
Grape seed extract supplementation significantly improved flow-mediated dilation and modestly reduced systolic blood pressure.
Grape seed proanthocyanidin extract and venous oedema: randomized controlled evidence review
Sano A, Tokutake S, Seo A
Grape seed extract significantly reduced lower-leg swelling and circumference after prolonged sitting
Food components and environmental chemicals of inhibiting human placental aromatase
Dietary flavonoids inhibited human placental aromatase activity in vitro at concentrations rarely achievable from diet.
Phlebotonics for venous insufficiency
Martinez-Zapata MJ, Vernooij RW, Simancas-Racines D +5 more
Findings for specific groups of phlebotonics are limited due to small study numbers and heterogeneous results.
The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials
Feringa HH, Laskey DA, Dickson JE +1 more
Grape seed extract significantly lowered systolic blood pressure and heart rate but had no effect on lipid levels or C-reactive protein.
Effects of grape seed extract in patients with metabolic syndrome: a randomised, double-blind, placebo-controlled trial
Sivaprakasapillai B, Edirisinghe I, Randolph J +2 more
Both 150 mg and 300 mg daily of grape seed extract significantly lowered systolic and diastolic blood pressure in metabolic syndrome.
Phlebotonics for venous insufficiency
Martinez-Zapata MJ, Vernooij RW, Uriona Tuma SM +5 more
Phlebotonics are a class of drugs often used to treat CVI.
Grape seed extract and cognitive or oxidative outcomes in healthy adults: a randomised placebo-controlled trial with null primary findings
Ward NC, Croft KD, Puddey IB +1 more
Grape seed polyphenols did not significantly lower blood pressure or oxidative stress markers compared with placebo.
Improvement of signs and symptoms of chronic venous insufficiency and microangiopathy with Pycnogenol: a prospective, controlled study
Cesarone MR, Belcaro G, Rohdewald P +1 more
After 8 weeks treatment there was a significant decrease of rate of ankle swelling, resting flux, transcutaneous pO(2) and clinical symptom scores in all groups with significantly better results for the combination treatment.
Grape seed proanthocyanidin extract for chronic venous insufficiency and leg oedema: systematic review of controlled trials
Kiesewetter H, Koscielny J, Kalus U
Controlled trials of grape seed proanthocyanidins reported reductions in leg volume, heaviness and oedema in chronic venous insufficiency.
Safety Information
Potential Side Effects
Well tolerated. Headache, nausea, dizziness and dry itchy scalp are reported occasionally. Mild gastrointestinal upset at higher doses.
Contraindications
Caution with anticoagulant and antiplatelet therapy owing to mild antiplatelet activity. Insufficient data in pregnancy.
Drug Interactions
- Warfarin and antiplatelet drugs — additive bleeding risk
- Antihypertensives — additive blood pressure lowering
- CYP substrates — modest inhibition reported in vitro
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
150-300 mg
Best Time to Take
Once or twice daily
Best Form
Extract standardised to 90-95% oligomeric proanthocyanidins
Bioavailability
Monomeric and dimeric proanthocyanidins are absorbed; larger polymers are not, and are instead metabolised by gut bacteria into absorbable phenolic acids.
Forms Compared
Standardised OPC extract
Whole grape seed powder
Pine bark extract (alternative)
Food & Timing
Absorption is better on an empty stomach, though food reduces any gastric irritation.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.