A new study published in Archives of Internal Medicine provides the best evidence yet that drinking black tea can lower blood pressure. Jonathan M. Hodgson and colleagues randomized 95 regular tea drinkers to either 3 cups per day of either black tea (containing 429 mg of polyphenols and 96 mg of caffeine) or placebo.
At 3 and 6 months, the mean 24-hour ambulatory BP was lower in the tea group than in the placebo group:
- systolic BP at 3 months: –2.7 (–4.7 to –0.8) mm Hg (p= .006)
- systolic BP at 6 months: –2.0 (–4.0 to –0.0) mm Hg (p=.05)
- diastolic BP at 3 months: –2.3 (–3.6 to –0.9) mm Hg (p<.001)
- diastolic BP at 6 months: –2.1 (–3.5 to –0.7) mm Hg (p= .003)
The authors noted that previous trials had been unable to detect a blood-pressure lowering effect of black tea, but these trials may have been underpowered or did not last long enough. The authors also briefly speculated on possible mechanisms of action, noting that tea can improve endothelial function and that flavonoids may have an effect on body weight and visceral fatness.
The authors calculated that the reductions in blood pressure found in the study “would be associated with a 10% reduction in the prevalence of hypertension and a 7% to 10% reduction in the risk of cardiovascular disease.”