Black Tea Lowers Blood Pressure

Black tea is rich in flavonoids, an antioxidant compound associated with heart health.  Jonathan Hodgson, from the University of Western Australia (Australia), and colleagues enrolled 95 men and women, ages 35 to 75 years, all of whom were regular tea drinkers, in a randomized double-blind trial. The study subjects had a mean body mass index of 25 kg/m2 and a mean daytime ambulatory systolic blood pressure of 121 mm Hg at baseline. During the first four-week period of the study, all of the participants consumed a low-flavonoid diet along with three cups of regular leaf tea per day.  During the six-month intervention period, the participants were randomized to either drink three cups per day of 1,493-mg powdered black tea solids that contained 429 mg of polyphenols and 96 mg of caffeine, or a placebo drink matched in flavor and caffeine content.  Whereas from the study start to six months, there were no changes in energy and nutrient intake, urinary sodium and potassium excretion, or body weight in either group, the researchers noted significant differences in 24-hour ambulatory blood pressure, primarily observed in daytime.  Among the subjects who drank the tea, systolic blood pressure readings were 2.7 mm Hg lower at three months and 2.0 mm Hg lower at six months; diastolic readings were 2.3 and 2.1 mm Hg lower, respectively.  Positing that tea consumption improves endothelial function, the study authors submit that tea flavonoids reduce levels of endothelin and thereby contribute to reduced vascular tone and lower blood pressure.