Effect of Grape Polyphenols on Blood Pressure: A Meta-Analysis of Randomized Controlled Trials

Systematic review and meta-analysis of 10 randomized controlled trials in adults. Participants included healthy adults and people with hypertension, metabolic syndrome, high vascular risk, or coronary disease; mean ages ranged from 31.4 to 63.7 years and BMI from 23.2 kg/m2 to 36 kg/m2.

Daily oral grape polyphenol supplementation was evaluated across randomized trials, with doses ranging from 150 mg/day to 1400 mg/day. Two trials contributed both low-dose and high-dose arms, and one trial excluded the alcoholized arm from analysis because alcohol could affect blood pressure.

Daily grape polyphenol intake modestly reduced systolic blood pressure overall, but it did not significantly reduce diastolic blood pressure. For systolic blood pressure, 12 comparisons showed a weighted mean difference of -1.48 mmHg (95% CI: -2.79 to -0.16; P = 0.03), with low heterogeneity (I2 = 32%, P = 0.14) and no evidence of publication bias. The blood pressure effect was larger in low-dose trials (< 733 mg/day) and in participants with metabolic syndrome, where systolic blood pressure fell by WMD:-7.05 mmHg (95% CI: -10.97 to -3.12). Overall, the findings support a small antihypertensive effect of grape polyphenols, especially at lower doses and in metabolic syndrome.

The evidence base was small and heterogeneous in terms of population, dose, and background lifestyle factors. Few hypertensive participants were included, and the included trials varied in dosing regimens and study characteristics, limiting generalizability. More larger, well-designed trials in hypertensive populations are needed to confirm the effect.