Black Tea Lowers Blood Pressure in Small Trial

January 24, 2012

January 24, 2012 (Boston, Massachusetts) — Drinking black tea appears to reduce the risk of developing high blood pressure, research shows [1]. Three daily cups, which provided approximately 400 mg/day of polyphenols, reduced systolic and diastolic blood pressure between 2 to 3 mm Hg, according to researchers.

"A large proportion of the general population has blood pressure within the range included in this trial, making results of the trial applicable to individuals at increased risk of hypertension," write Dr Jonathan Hodgson (University of Western Australia, Perth) and colleagues in a research letter published in the January 23, 2012 issue of the Archives of Internal Medicine.

Black tea is a common source of flavonoids, which have been suggested to contribute to vascular health. The researchers point out that they have shown that flavonoids augment nitric-oxide status and reduce plasma concentration of endothelin-1, both of which could contribute to reductions in vascular tone and reduced blood pressure.

In their study, the group randomized 95 men and women with a daytime ambulatory systolic blood pressure between 115 and 150 mm Hg to three cups of black tea daily or to placebo that matched the tea in flavor and caffeine content (approximately 96 mg of caffeine per day). There were no significant differences between patient groups at baseline.

Daily consumption of the tea resulted in a significantly lower 24-hour systolic and diastolic blood pressure compared with the control arm. The net-effect difference in systolic blood pressure at three and six months was -2.7 mm Hg and -2.0 mm Hg, respectively (p=0.006 at three months, p=0.05 at six months). Diastolic blood pressure was reduced 2.3 mm Hg and 2.1 mm Hg at three and six months, respectively (p<0.001 at three months, p=0.003 at six months).

"At a population level, the observed differences in BP would be associated with a 10% reduction in the prevalence of hypertension and a 7% to 10% reduction in the risk of cardiovascular disease," write Hodgson and colleagues. "Therefore, given the high prevalence of hypertension worldwide and the importance of hypertension as a risk factor for cardiovascular and total mortality, these findings have important public-health implications."


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