Grape Seed Extract
A cheap, well-tolerated source of oligomeric proanthocyanidins with a small but consistent blood-pressure effect and decent evidence in venous insufficiency.
Moderate for a small systolic blood-pressure reduction (meta-analyses of randomised trials; effect of a few mmHg, larger in obese and metabolic-syndrome groups) and for improved flow-mediated dilation. Moderate for chronic venous insufficiency and leg oedema. Weak for the broader antioxidant, cognitive and anti-cancer claims. Effects: 4–8 weeks.
Grape seed extract concentrates the oligomeric proanthocyanidins (OPCs) found in grape seeds — the same polyphenol family as pine bark, at a fraction of the price. Meta-analyses of randomised trials show a modest but reproducible reduction in systolic blood pressure and heart rate, most pronounced in younger, obese or metabolic-syndrome participants, and it improves flow-mediated dilation. It also reduces leg oedema and symptoms in chronic venous insufficiency. It is not a substitute for antihypertensive medication — the effect size is a few mmHg — and the antioxidant and anti-cancer claims made for it far outrun the human evidence.
- Form
- Standardised to 90–95% OPCs (proanthocyanidins). Doses in trials are usually of the standardised extract, not raw seed powder — check the label states OPC content.
- Dose
- 100–300 mg/day of standardised extract. Blood-pressure meta-analyses pool doses of roughly 100–800 mg/day; 150–300 mg/day is the practical range.
- Timing
- With food, split twice daily if above 200 mg.
- Schedule
- Daily. Blood-pressure and endothelial effects appear within 4–8 weeks. Reassess at 3 months with home readings.
- Side effects
- Well tolerated. Headache, dry scalp, dizziness and nausea are the common complaints. High doses may cause GI upset.
- Interactions
- Anticoagulants and antiplatelets — antiplatelet activity, additive bleeding risk. Antihypertensives — additive lowering. May inhibit CYP enzymes at high doses, theoretically affecting drugs metabolised through them. Iron — polyphenols reduce non-haem iron absorption, so separate by 2 hours if you're treating deficiency.
- Contraindications
- Bleeding disorders, or within 2 weeks of surgery. Pregnancy and breastfeeding (insufficient data). Known grape allergy.
- Lab markers
- Home blood pressure — the endpoint most likely to move. Lipid panel and hs-CRP if using it for vascular reasons. Ferritin if you're also treating iron deficiency.
- Food sources
- Whole grapes, red wine and grape juice contain proanthocyanidins, but far below extract doses — and the seeds themselves are where they concentrate. Also present in cocoa, apples, berries and pine bark.
Pairs with
Pycnogenol and Centella asiatica (same venous and microcirculatory target). Beetroot or citrulline for a nitric-oxide-driven blood-pressure stack. Vitamin C to regenerate the polyphenols. Keep 2 hours away from iron supplements.
within Polyphenols & antioxidants