−38% hsCRP
An inflammation marker fell in 4 weeks
hsCRP, mg/L · lower is better
32 adults with type 2 diabetes (16 men, 16 women) at 600mg a day, four times our 150mg. No significant change on placebo.
View study →Grape Seed Extract
foundation
Abstract
Grape Seed Extract contains high concentrations of proanthocyanidins — potent antioxidant compounds that support cardiovascular health. These polyphenols work through multiple mechanisms: neutralizing free radicals, reducing inflammation, and may improve blood vessel function through enhanced nitric oxide production. Better blood flow supports energy and physical performance.
We standardize our extract to 95% polyphenols, ensuring consistent potency of the active compounds in every dose. That standardization matters — raw grape seed extract varies widely in composition, so locking in the polyphenol content is what separates a reliable ingredient from a label claim.
150mg
Per Serving
5 featured studies29 published studies
Growing Evidence
Evidence Rating
This ingredient is part of RBRN Vitality
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Grape Seed Benefits — What Studies Found
No ingredient works if blood can’t carry it where it’s needed. Grape seed extract supports circulation and nitric oxide production from the ground up.
+52% glutathione
Glutathione, the body’s own antioxidant, rose
Whole-blood glutathione · higher is better
Same 4-week trial and 600mg dose. Other oxidative-stress markers did not change.
View study →Blocked the enzyme that turns testosterone into estrogen
- Testosterone
- Estrogen
Grape seed extract inhibited aromatase in lab tests
Laboratory research only; not yet confirmed in people.
View study →Why a 150mg dose of Grape Seed Extract
Clinical studies showing cardiovascular benefits use doses ranging from 100-300mg of standardized grape seed extract. Our 150mg sits in the middle of this effective range.
- Mid-Range Dose 150mg sits within the 100-300mg range used in clinical trials on blood pressure and endothelial function.
- 95% Polyphenol Standardization Ensures a consistent, concentrated dose of proanthocyanidins rather than variable raw seed material.
- Dual-Purpose Ingredient Supports cardiovascular health and blood flow while also contributing aromatase-inhibiting properties relevant to hormone balance.
- Consistent Study Outcomes Blood pressure reduction and antioxidant effects are among the more reliably demonstrated findings in grape seed research.
Clinical Dose Range
150mg · RBRN Vitality
0mg
500mg
100–300mg studied
Clinical studies use 100–300mg of standardized extract. Our 150mg at 95% polyphenols delivers potent antioxidant support within the effective range.
Grape Seed ExtractCardiovascular & Antioxidant Defense
Proanthocyanidins support nitric oxide and vascular function — the circulation that carries every other ingredient to where it needs to go.
01
Blood Pressure in Metabolic Syndrome
Sivaprakasapillai B, et al. (2009). Metabolism.
Source
Blood Pressure in Metabolic Syndrome
Sivaprakasapillai B, et al. (2009). Metabolism. Source
A study in subjects with metabolic syndrome found that grape seed extract significantly lowered both systolic and diastolic blood pressure compared to placebo. Blood pressure is a key indicator of cardiovascular health.
02
Endothelial Function
Clifton PM. (2004). Journal of Biomedicine & Biotechnology.
Source
Endothelial Function
Clifton PM. (2004). Journal of Biomedicine & Biotechnology. Source
Research shows grape seed extract improves flow-mediated dilation—a measure of how well blood vessels relax and expand. This indicates better endothelial function and nitric oxide availability.
03
Inflammation and Metabolic Markers
Kar P, et al. (2009). Diabetic Medicine.
Source
Inflammation and Metabolic Markers
Kar P, et al. (2009). Diabetic Medicine. Source
In type 2 diabetics at high cardiovascular risk, grape seed extract (at 600mg/day — four times our 150mg dose) significantly improved markers of inflammation (hsCRP decreased ~38%), blood glucose (fructosamine), and glutathione levels (increased ~52%). Effects at lower doses have not been separately studied.
04
Aromatase Inhibition
Kijima I, et al. (2006). Cancer Research.
Source
Aromatase Inhibition
Kijima I, et al. (2006). Cancer Research. Source
Laboratory studies demonstrate that grape seed extract inhibits aromatase activity and suppresses aromatase expression. This may help maintain testosterone-to-estrogen balance by reducing testosterone conversion.
05
Antioxidant Capacity
Nuttall SL, et al. (1998). Journal of Clinical Pharmacy and Therapeutics.
Source
Antioxidant Capacity
Nuttall SL, et al. (1998). Journal of Clinical Pharmacy and Therapeutics. Source
In a small 5-day trial (n=20), grape seed extract increased serum total antioxidant capacity, suggesting potential systemic antioxidant benefits.
Published Research
29 studiesEvery claim we make is grounded in peer-reviewed research. Tap any study to read the abstract.
Year
Title
Journal
Our Assessment: Grape Seed Extract
Growing Evidence
Evidence Rating
Good clinical evidence for blood pressure and antioxidant support. The aromatase-inhibiting properties are shown in lab research but haven't been confirmed in human hormone studies yet.
What’s Solid
- Blood pressure reduction is demonstrated in clinical trials
- Antioxidant activity is well-documented
- Endothelial function improvements are measurable
- Aromatase inhibition is shown in laboratory research
What Needs More Research
- Long-term cardiovascular outcome studies
- Translation of aromatase inhibition findings to meaningful hormone effects in humans
- Optimal dosing for different goals
- Direct comparisons with other cardiovascular compounds
How Grape Seed Fits the Formula
No ingredient works alone. Grape Seed was chosen because it amplifies — and is amplified by — specific formula partners.
Grape Seed
Fenugreek & Tongkat Ali
Grape seed extract shows aromatase-inhibiting properties in laboratory research. Fenugreek and tongkat ali may also influence testosterone-to-estrogen balance through different proposed mechanisms, though these pathways are still being studied. Multiple ingredients potentially addressing hormone balance from different angles.
Cellular Energy
Good blood flow delivers oxygen and nutrients to cells, supporting the cellular energy production addressed by NMN and PQQ. Circulation and cellular function are connected.
BioPerine®
BioPerine® enhances the absorption of various polyphenolic compounds. This may improve the bioavailability of grape seed extract’s active components.
Safety and Precautions
Considerations
Grape seed extract is generally well tolerated with minimal side effects in clinical trials.
Blood thinning
May have mild effects on platelet aggregation. Those on anticoagulant medications (warfarin, aspirin, etc.) should consult their healthcare provider.
Surgery
As with many supplements affecting blood clotting, consider discontinuing before scheduled surgery.
Pregnancy and lactation
Limited safety data; caution is advised.
Always consult with a healthcare professional before starting any new dietary supplement, especially if you have an existing medical condition or take prescription medications.
