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.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). The evidence base is small (only 6 studies), and one study found no effect on DBP in obese males, suggesting the benefit may be limited to specific populations.
GSE decreased resting DBP (75 ± 2 vs. 71 ± 3) compared to the placebo (DBP:71 ± 3 vs. 74 ± 3)
insulin, HOMA-IR, TC, TG, LDL-c, ALT, AST, AST/ALT, SBP, DBP and MAP decreased and QUICKi and HDL-c increased significantly (p-value for all < 0.05)
Intervention with grape seed extract may reduce systolic and diastolic blood pressure in subjects with hypertension or metabolic syndrome.
while there were no differences in HR, SV, DBP, TPR, and AoS.
GSE supplementation attenuated MAP at both workloads (40% VO2peak: 115 ± 1 vs. 112 ± 2 mmHg; 60% VO2peak: 126 ± 2 vs. 123 ± 2 mmHg)
GSE supplementation significantly reduced DBP (WMD: -2.20 mmHg, 95% CI: -3.79 to -0.60, I² = 88.8%)