Effect of Grape Polyphenols on Blood Pressure: A Meta-Analysis of Randomized Controlled Trials
What this study found
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…
- Study & population
- Systematic review and meta-analysis of 10 randomized controlled trials in adults.
- Intervention
- Daily oral grape polyphenol supplementation was evaluated across randomized trials, with doses ranging from 150 mg/day to 1400 mg/day.
- Key limitation
- The evidence base was small and heterogeneous in terms of population, dose, and background lifestyle factors.
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Open PDFOriginal abstract
Background The effect of grape polyphenols on blood pressure remains unclear, which we aimed to address via a meta-analysis study. Methods We conducted study trial searches in PubMed, Embase, and the Cochrane Library databases. Summary estimates of weighted mean differences and 95% confidence intervals were obtained by using fixed-effects models. Subgroup analyses were performed to identify the source of heterogeneity. The protocol details of our meta-analysis have been submitted to the international database of prospectively registered systematic reviews (registration number CRD42015019196). Results Ten studies were included in the present meta-analysis. Our results showed daily grape polyphenol intake could significantly reduce systolic blood pressure by 1.48 mmHg when compared to control subjects (12 comparisons; -1.48 [-2.79 to -0.16] mmHg; P = 0.03). Subgroup analyses indicated larger reduction was identified in the intake of low-dose of grape polyphenols (< 733 mg/day, median level of the included studies) or patients with metabolic syndrome. Contrarily, diastolic blood pressure was not significantly decreased in the grape polyphenols group as compared to controls. No significant heterogeneity or publication bias was detected in the meta-analysis of either systolic or diastolic blood pressure. Conclusions Daily grape polyphenol intake can significantly reduce the systolic blood pressure in humans, although the reduction is modest when compared with anti-hypertensive medications. Larger, better designed trials, that specifically include hypertensive subjects, are required to verify our results in the future.