Quercetin May Reduce Hypertension

by | Jul 1, 2008 | 2008, Blood Pressure, Cardiovascular Health, Flavonoids, Quercetin, Stroke

Written by Susan Sweeny Johnson, PhD, Biochem. This double blind, randomized, crossover study demonstrates how quercetin supplementation reduced systolic blood pressure in 22 stage 1 hypertensive patients. This reduction decreases death from stroke by 14% and death from cardiac heart disease by 9%.

Quercetin, an antioxidant flavonoid found in apples, red wine, onions and berries, has been shown to aid in preventing cardiovascular disease and stroke (1-3).  Studies have shown that quercetin lowers blood pressure in hypertensive animals and prevents hypertension from occurring when arteries are physically constricted (4, 5). No quercetin supplementation human studies of hypertensive patients had previously been done.

In a new, double-blind, randomized, crossover study* 19 prehypertensive patients (137+ 2/86 + 1 mm Hg systolic/diastolic BP) and 22 stage 1 hypertensive patients (148 + 2/96 + 1 mm Hg systolic/diastolic BP) were given either a placebo or 730 mg of quercetin for 28 days. After one week of washout**, they were given the alternate regimen. Efficacy of supplementation was monitored by blood levels of quercetin: 695 + 103 nmol/L after placebo treatment and 1419 + 189 nmol/L after quercetin treatment. Patients selected for the study were not taking medication for high blood pressure and were otherwise healthy and led healthy lifestyles.

Blood pressure was not altered in pre-hypertensive patients after quercetin supplementation. In contrast, reductions in (P < 0.01) systolic (-7.2mm Hg) and diastolic (-5.2mm Hg) blood pressures were observed in stage 1 hypertensive patients after quercetin treatment. Measurements of oxidative stress indicated no change with or without quercetin supplementation, despite evidence that quercetin acts as an antioxidant (6).

Recent AHA statistics estimate that over 50 million Americans suffer from hypertension (7). Deaths from stroke and heart disease increase in direct proportion to blood pressure, emphasizing the importance of blood pressure control (8). “Based on risk assessment summarized in the 7th Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, the risk of death from ischemic heart disease and stroke in prehypertensive patients used in the present study is double that of individuals with blood pressure of 115/75 mm Hg and nearly four times greater in stage 1 hypertensive patients (9).” The quercetin-induced lowering of systolic blood pressure observed in this study in stage 1 hypertensive subjects (-7.2 mm Hg) is significant because reductions of this magnitude are associated with a decrease in mortality of ~14% from stroke and ~9% from coronary heart disease (8).

Lifestyle modification has been emphasized in prehypertensive and hypertensive individuals as an initial intervention to control blood pressure (9). The reduction of blood pressure in this study in stage 1 hypertensive subjects after quercetin supplementation is similar to those experienced following sodium reduction, weight reduction, increased physical activity, or alcohol reduction as discussed in the Dietary Approaches to Stop Hypertension diet (10). Thus, it appears that the effects of quercetin supplementation are consistent with current recommended lifestyle modifications used to reduce blood pressure.

Further larger human studies using a more diverse ethnic population should be performed to confirm these results.

High blood pressure (hypertension) was listed as a primary or contributing cause of death for 277,000 Americans in 2002. About 28% of American adults have pre-hypertension and about 90% of middle–aged adults will develop high blood pressure in the remainder of their lifetime. It is estimated that the direct and indirect costs of high blood pressure will be $63.5 billion in the year 2006 (11).

*A study that is double-blind means that neither the patient nor the researcher knows who is getting the placebo. Randomized means that the individual patients who receive the placebo or quercetin are decided by random chance. Crossover means the group that received the placebo first, received the quercetin for the next test period and vice versa.
**Washout is the stage in a crossover study when treatment is withdrawn before the second treatment is given. Washout periods are usually necessary because of the possibility that the intervention administered first can affect the outcome variable for some time after treatment ceases.

Source: Edwards, Randi L., Tiffany Lyon, Sheldon E. Litwin, Alexander Rabovsky, J. David Symons, and Thunder Jalili. “Quercetin reduces blood pressure in hypertensive subjects.” The Journal of nutrition 137, no. 11 (2007): 2405-2411.

© 2007 American Society for Nutrition

Posted July 1, 2008.

References:

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  7. American Heart Association. Heart disease and stroke statistics: 2004 update. Dallas: AHA; 2003.
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  9. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, Jones DW, Materson BJ, Oparil S, et al. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension. 2003;42:1206–52.
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  11. See the Centers for Disease Control and Prevention website.