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

View Article: PubMed Central - PubMed

ABSTRACT

Background: Quercetin, 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 results: We 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.

Conclusions: The 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.

No MeSH data available.


Forest plot displaying weighted mean difference and 95% CIs for the impact of quercetin on diastolic blood pressure in different subgroups of trials stratified according to the administered quercetin dose and duration of supplementation.
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jah31607-fig-0004: Forest plot displaying weighted mean difference and 95% CIs for the impact of quercetin on diastolic blood pressure in different subgroups of trials stratified according to the administered quercetin dose and duration of supplementation.

Mentions: Combined analysis of 9 RCT arms revealed a significant reduction of DBP (WMD: −2.63 mm Hg, 95% CI: −3.26, −2.01, P<0.001) following supplementation with quercetin (Figure 2 lower part). Removal of the study by Zahedi et al33 yielded an effect size equivalent to −0.98 mm Hg (95% CI: −2.44, 0.49, P=0.191). In subgroup analysis, a marginally significant effect was found in the subset of trials with <8 weeks of follow‐up (WMD: −1.85 mm Hg, 95% CI: −3.72, 0.02, P=0.053) but not in the subset lasting ≥8 weeks (WMD: −0.88 mm Hg, 95% CI: −3.23, 1.47, P=0.464) (Figure 3). When the studies were categorized according to administered quercetin dose, there was a greater DBP‐reducing effect in trials with ≥500 mg/day (WMD: −2.98 mm Hg, 95% CI: −3.64, −2.31, P<0.001) versus those with <500 mg/day dosage (WMD: −0.24 mm Hg, 95% CI: −2.00, 1.52, P=0.788) (Figure 4). This result was also consistent when the dose classification was set at ≤500 and >500 mg/day (P>0.05 and <0.05, respectively). However, adjusted indirect comparison did not suggest any significant difference between either of the dose (ΔWMD: −2.74 mm Hg, 95% CI: −4.34, −1.14, Δz‐score: −3.36, P>0.05) and supplementation duration (ΔWMD: −0.88 mm Hg, 95% CI: −2.68, 0.92, Δz‐score: −0.96, P>0.05) subgroup pairs.


Effects of Quercetin on Blood Pressure: A Systematic Review and Meta ‐ Analysis of Randomized Controlled Trials
Forest plot displaying weighted mean difference and 95% CIs for the impact of quercetin on diastolic blood pressure in different subgroups of trials stratified according to the administered quercetin dose and duration of supplementation.
© Copyright Policy - creativeCommonsBy-nc
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015358&req=5

jah31607-fig-0004: Forest plot displaying weighted mean difference and 95% CIs for the impact of quercetin on diastolic blood pressure in different subgroups of trials stratified according to the administered quercetin dose and duration of supplementation.
Mentions: Combined analysis of 9 RCT arms revealed a significant reduction of DBP (WMD: −2.63 mm Hg, 95% CI: −3.26, −2.01, P<0.001) following supplementation with quercetin (Figure 2 lower part). Removal of the study by Zahedi et al33 yielded an effect size equivalent to −0.98 mm Hg (95% CI: −2.44, 0.49, P=0.191). In subgroup analysis, a marginally significant effect was found in the subset of trials with <8 weeks of follow‐up (WMD: −1.85 mm Hg, 95% CI: −3.72, 0.02, P=0.053) but not in the subset lasting ≥8 weeks (WMD: −0.88 mm Hg, 95% CI: −3.23, 1.47, P=0.464) (Figure 3). When the studies were categorized according to administered quercetin dose, there was a greater DBP‐reducing effect in trials with ≥500 mg/day (WMD: −2.98 mm Hg, 95% CI: −3.64, −2.31, P<0.001) versus those with <500 mg/day dosage (WMD: −0.24 mm Hg, 95% CI: −2.00, 1.52, P=0.788) (Figure 4). This result was also consistent when the dose classification was set at ≤500 and >500 mg/day (P>0.05 and <0.05, respectively). However, adjusted indirect comparison did not suggest any significant difference between either of the dose (ΔWMD: −2.74 mm Hg, 95% CI: −4.34, −1.14, Δz‐score: −3.36, P>0.05) and supplementation duration (ΔWMD: −0.88 mm Hg, 95% CI: −2.68, 0.92, Δz‐score: −0.96, P>0.05) subgroup pairs.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Quercetin, 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&#8208;analysis of available randomized controlled trials.

Methods and results: We searched PUBMED, Cochrane Library, Scopus, and EMBASE up to January 31, 2015 to identify placebo&#8208;controlled randomized controlled trials investigating the effect of quercetin on BP. Meta&#8208;analysis was performed using either a fixed&#8208;effects or random&#8208;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&#8208;analysis showed significant reductions both in systolic BP (WMD: &minus;3.04&nbsp;mm&nbsp;Hg, 95% CI: &minus;5.75, &minus;0.33, P=0.028) and diastolic BP (WMD: &minus;2.63&nbsp;mm&nbsp;Hg, 95% CI: &minus;3.26, &minus;2.01, P&lt;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&#8208;reducing effect in randomized controlled trials with doses &ge;500&nbsp;mg/day (WMD: &minus;4.45&nbsp;mm&nbsp;Hg, 95% CI: &minus;7.70, &minus;1.21, P=0.007 and &minus;2.98&nbsp;mm&nbsp;Hg, 95% CI: &minus;3.64, &minus;2.31, P&lt;0.001, respectively), and lack of a significant effect for doses &lt;500&nbsp;mg/day (WMD: &minus;1.59&nbsp;mm&nbsp;Hg, 95% CI: &minus;4.44, 1.25, P=0.273 and &minus;0.24&nbsp;mm&nbsp;Hg, 95% CI: &minus;2.00, 1.52, P=0.788, respectively), but indirect comparison tests failed to significant differences between doses.

Conclusions: The results of the meta&#8208;analysis showed a statistically significant effect of quercetin supplementation in the reduction of BP, possibly limited to, or greater with dosages of &gt;500&nbsp;mg/day. Further studies are necessary to investigate the clinical relevance of these results and the possibility of quercetin application as an add&#8208;on to antihypertensive therapy.

No MeSH data available.