Effects of Quercetin on Blood Pressure: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials

Abstract

BackgroundQuercetin, the most abundant dietary flavonol, has antioxidant effects in cardiovascular disease, but the evidence regarding its effects on blood pressure (BP) has not been conclusive. We assessed the impact of quercetin on BP through a systematic review and meta‐analysis of available randomized controlled trials.Methods and ResultsWe searched PUBMED, Cochrane Library, Scopus, and EMBASE up to January 31, 2015 to identify placebo‐controlled randomized controlled trials investigating the effect of quercetin on BP. Meta‐analysis was performed using either a fixed‐effects or random‐effect model according to I2 statistic. Effect size was expressed as weighted mean difference (WMD) and 95% CI. Overall, the impact of quercetin on BP was reported in 7 trials comprising 9 treatment arms (587 patients). The results of the meta‐analysis showed significant reductions both in systolic BP (WMD: −3.04 mm Hg, 95% CI: −5.75, −0.33, P=0.028) and diastolic BP (WMD: −2.63 mm Hg, 95% CI: −3.26, −2.01, P<0.001) following supplementation with quercetin. When the studies were categorized according to the quercetin dose, there was a significant systolic BP and diastolic BP‐reducing effect in randomized controlled trials with doses ≥500 mg/day (WMD: −4.45 mm Hg, 95% CI: −7.70, −1.21, P=0.007 and −2.98 mm Hg, 95% CI: −3.64, −2.31, P<0.001, respectively), and lack of a significant effect for doses <500 mg/day (WMD: −1.59 mm Hg, 95% CI: −4.44, 1.25, P=0.273 and −0.24 mm Hg, 95% CI: −2.00, 1.52, P=0.788, respectively), but indirect comparison tests failed to significant differences between doses.ConclusionsThe results of the meta‐analysis showed a statistically significant effect of quercetin supplementation in the reduction of BP, possibly limited to, or greater with dosages of >500 mg/day. Further studies are necessary to investigate the clinical relevance of these results and the possibility of quercetin application as an add‐on to antihypertensive therapy.

Dissection of the Effects of Quercetin on Mouse Myocardium

“…Clinical studies have demonstrated the potential benefits of quercetin in cardiovascular diseases . However, our results indicate that caution should be exercised, especially in subjects that are more sensitive to β‐agonists.…”

“…Cardiovascular effects of flavonoids have already been demonstrated [12] such as reduction in blood pressure [13] and by inducing lipid-lowering effects in the management of dyslipidaemias [14]. Important to note here is that quercetin and 3-methylquercetin were shown to have a positive chronotropic effect on the right guinea-pig atrium through b-adrenergic mechanism [15], and penta-O-ethylquercetin was shown to induce a rapid and transient fall in arterial blood pressure in rats mainly through inhibition of cardiac cyclic AMP phosphodiesterase [16].…”

Haemodynamic effects of the flavonoid quercetin in rats revisited

“…Reports on the BP-lowering action of quercetin in humans are not univocal. In the most recent systematic review and meta-analysis, a small (−3 mmHg) effect was found (Serban et al, 2016). Significant BP reductions occurred only when doses of quercetin exceeded 500 mgÁday −1 .…”

“…While other studies have explored the antihypertensive effects of quercetin further, controversy exists about the potential mechanisms involved, as well the magnitude of the effect and the potential clinical relevance (Carlstrom et al, ; Larson, Symons, & Jalili, ; Monteiro, Franca‐Silva, Alves, Porpino, & Braga, ; Sanchez et al, ). This is possibly due to publication bias (Serban et al, ), since negative studies on quercetin have been rarely published. Recently, we discovered that in isolated mesenteric arteries, quercetin increased the potency of tamsulosin to inhibit phenylephrine‐induced contractions by a factor >10 (Vrolijk et al, ).…”

Effect of quercetin on the brain-derived neurotrophic factor gene expression in the rat brain

“…These activities of quercetin have been attributed mainly to its antioxidant capacity, such as its free radical scavenger activity and by the induction of Nuclear factor (erythroid-derived 2)-like 2 and the consequent upregulation of antioxidant enzymes (28,29). There are some studies on the in vivo effects of quercetin in patients suffering from a disease which is associated with oxidative stress such as high blood pressure (30), sarcoidosis (31) and rheumatoid arthritis (32).These studies suggest that quercetin improves antioxidant defense system and reduces pro-infl ammatory cytokines such as TNFα and IL-8. Several studies have also demonstrated that various poly phenols with neuroprotective activity such as resveratrol, apigenin, luteolin and green tea increase expression of BDNF mRNA (33)(34)(35).…”