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Evidence-Based Supplement Research
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New evidence

Grape seed extract lowered diastolic BP by 4 mmHg in a week — but only in men with elevated hypertension, and systolic BP didn't budge.

This short-term study adds to a growing body of evidence that grape seed extract may modestly lower diastolic blood pressure, though the effect appears limited to certain blood pressure measures and may not generalize beyond men with elevated hypertension.

In a double-blind trial, men with elevated blood pressure who took grape seed extract for a week saw their diastolic (bottom number) drop by an average of 4 mmHg, while the placebo group saw a slight rise. The reduction occurred because the supplement widened their blood vessels, not because it changed heart rate or nervous system activity. However, systolic (top number) and heart rate remained unchanged, and the results may not apply to women or people with normal blood pressure.

Where this fits in the evidence

Pillser has synthesized 6 studies on Red Grape for Reduced Diastolic Blood Pressure — overall evidence strength: High.

Across 6 studies, 5 reported beneficial effects of red grape supplement on diastolic blood pressure, with effect sizes ranging from small to moderate. One study found no significant effect. The evidence, including meta-analyses and RCTs, indicates a small reduction in DBP, with the most notable effects seen in populations with hypertension or metabolic syndrome. Median study duration was 34 days, suggesting short-term benefits.

The study

Effect of 7-day dietary supplementation with grape seed extract on cardiac autonomic and hemodynamic responses in elevated and stage 1 hypertension.

  • Randomized Controlled Trial (RCT)
  • 2025-05
  • Clinical physiology and functional imaging
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This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.

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