Grape seed extract
Four meta-analyses found small blood pressure reductions, though they disagree on whether systolic or diastolic pressure fell. Pooled trials found lower fasting glucose, and results on cholesterol differ between reviews. One open-label trial reported shorter venous reflux in varicose veins, and one crossover trial less leg swelling while sitting. No safety review specific to grape seed was sourced.
- Status
- Dietary supplement in the US.
- Also called
- GSE, Vitis vinifera seed extract, grape seed proanthocyanidin extract, GSPE, oligomeric proanthocyanidins, OPC, OPCs, procyanidins
- Taken for
- blood pressure, varicose veins, venous insufficiency, leg swelling, swelling, cholesterol, blood sugar, inflammation
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help3
- ModerateShown to lower fasting glucose slightly in adults across 50 trials, with no change in HbA1c.
- LimitedOne trial without placebo found shorter venous reflux time and lower symptom scores with 150 mg twice a day in adults with varicose veins.
- LimitedOne small trial found less leg swelling during 6 hours of sitting in healthy Japanese women.
Reported risks1
What people take it for, and what was found
Shown to help3
Blood sugar
Shown to lower fasting glucose slightly in adults across 50 trials, with no change in HbA1c.
Venous insufficiency and varicose veins
One trial without placebo found shorter venous reflux time and lower symptom scores with 150 mg twice a day in adults with varicose veins.
The numbers and sources
- Effect
- In 176 adults with varicose veins and venous reflux, 150 mg twice a day plus lifestyle changes for 12 weeks shortened venous reflux time more than lifestyle changes alone, and lowered venous severity and quality of life symptom scores [6]. A Cochrane review of phlebotonics included 1 grape seed extract trial and reports results for all phlebotonics together [7].
- Population
- 176 adults aged 19 to 80 with varicose veins [6].
- Sources
- [6], [7]
- Caveats
- The varicose vein trial was open-label with no placebo, and its abstract gives no effect sizes [6].
Leg swelling while sitting
One small trial found less leg swelling during 6 hours of sitting in healthy Japanese women.
The numbers and sources
- Effect
- In a double-blind, placebo-controlled crossover study, a single dose and a 14-day course both reduced the increase in leg volume, body extracellular fluid and leg water during 6 hours of sitting [8].
- Population
- Healthy Japanese women. The abstract does not give the number [8].
- Sources
- [8]
- Caveats
- One small study in healthy women. The abstract gives no effect sizes [8].
Mixed results3
Blood pressure
Mixed results: reviews found lower blood pressure, by up to about 6 mmHg systolic, but disagree on whether systolic or diastolic pressure falls.
The numbers and sources
- Effect
- In 16 trials (810 people), grape seed extract lowered systolic pressure by 6.08 mmHg (95% CI -10.74 to -1.42) and diastolic pressure by 2.80 mmHg (95% CI -4.42 to -1.19) [1]. An earlier meta-analysis of 9 RCTs (390 people) found systolic pressure 1.54 mmHg lower (95% CI -2.85 to -0.22) and no change in diastolic pressure [2]. A 2022 meta-analysis of 19 trials found diastolic pressure 2.20 mmHg lower (95% CI -3.79 to -0.60) and no significant change in systolic pressure (-3.55 mmHg, 95% CI -7.59 to 0.49) [3]. A meta-analysis of proanthocyanidins from any source (6 RCTs, 376 people) found systolic pressure 4.60 mmHg lower and diastolic pressure 2.75 mmHg lower [4].
- Population
- Adults, including people with obesity, metabolic syndrome or raised blood pressure [1][2][3][4].
- Sources
- [1], [2], [3], [4]
- Caveats
- The reviews disagree on which pressure falls. Heterogeneity in the 2022 analysis was high (I² 88.8% diastolic, 97.4% systolic) [3]. The proanthocyanidin review included sources other than grape seed [4].
Cholesterol
Limited evidence: a 50-trial review found lower total and LDL cholesterol and triglycerides, while an earlier review found no effect on lipids.
The numbers and sources
- Effect
- Across 50 trials, grape seed extract lowered total cholesterol (WMD -6.03, 95% CI -9.71 to -2.35), LDL cholesterol (WMD -4.97) and triglycerides (WMD -6.55). HDL did not change [5]. An earlier meta-analysis of 9 RCTs found no significant effect on lipid levels [2].
- Population
- Adults in RCTs [5][2].
- Sources
- [5], [2]
- Caveats
- The two reviews disagree.
Inflammation
Limited evidence: a 50-trial review found lower CRP, while an earlier review found no effect.
The numbers and sources
Doses studied
The varicose vein trial used 150 mg twice a day for 12 weeks [6]. In the proanthocyanidin review, doses under 245 mg a day lowered systolic, diastolic and mean arterial pressure in subgroup analysis [4].
Risks
Reported risks1
Adverse events in venous trials
Limited evidence: across phlebotonic trials, adverse events were slightly more common than on placebo, mostly digestive. Only one trial tested grape seed extract.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Across 37 trials of phlebotonics (5,789 participants), adverse events were slightly more common than on placebo (RR 1.14, 95% CI 1.02 to 1.27), mostly digestive [7].
- Population
- Adults with chronic venous insufficiency in RCTs [7].
- Sources
- [7]
- Caveats
- This pools all phlebotonics, and only one included trial tested grape seed extract. No review of grape seed extract safety was sourced.
Sources
- Zhang H, Liu S, Li L, et al. The impact of grape seed extract treatment on blood pressure changes: A meta-analysis of 16 randomized controlled trials. Medicine. 2016. https://doi.org/10.1097/MD.0000000000004247
- Feringa HH, Laskey DA, Dickson JE, Coleman CI. The effect of grape seed extract on cardiovascular risk markers: a meta-analysis of randomized controlled trials. Journal of the American Dietetic Association. 2011. https://doi.org/10.1016/j.jada.2011.05.015
- Foshati S, Nouripour F, Sadeghi E, Amani R. The effect of grape (Vitis vinifera) seed extract supplementation on flow-mediated dilation, blood pressure, and heart rate: A systematic review and meta-analysis of controlled trials with duration- and dose-response analysis. Pharmacological Research. 2022. https://doi.org/10.1016/j.phrs.2021.105905
- Ren J, An J, Chen M, et al. Effect of proanthocyanidins on blood pressure: A systematic review and meta-analysis of randomized controlled trials. Pharmacological Research. 2021. https://doi.org/10.1016/j.phrs.2020.105329
- Asbaghi O, Nazarian B, Reiner Ž, et al. The effects of grape seed extract on glycemic control, serum lipoproteins, inflammation, and body weight: A systematic review and meta-analysis of randomized controlled trials. Phytotherapy Research. 2020. https://doi.org/10.1002/ptr.6518
- Bae S, Kim H, Son NH, et al. Vitis vinifera seed extract reduces venous reflux time in patients with varicose veins: VICTORY randomized controlled trial. Journal of Vascular Surgery: Venous and Lymphatic Disorders. 2026. https://doi.org/10.1016/j.jvsv.2025.102355
- Martinez-Zapata MJ, Vernooij RW, Simancas-Racines D, et al. Phlebotonics for venous insufficiency. Cochrane Database of Systematic Reviews. 2020. https://doi.org/10.1002/14651858.CD003229.pub4
- Sano A, Tokutake S, Seo A. Proanthocyanidin-rich grape seed extract reduces leg swelling in healthy women during prolonged sitting. Journal of the Science of Food and Agriculture. 2013. https://doi.org/10.1002/jsfa.5773