People who drink black tea throughout the day may get the benefit of a slight reduction in their blood pressure, suggests a new Australian study.
Although the study cannot identify specific components of the tea that might lead to a drop in blood pressure, the researchers speculate flavonoids, natural compounds found in many plants such as tea, play a role.
The study, published in the Archives of Internal Medicine, randomly assigned 95 Australians with normal blood pressure to two groups. One group drank black tea and another drank a beverage similar in taste and caffeine content.
Before the study started, the participants' blood pressure throughout the day was about 121/72 millimetres of mercury (mm Hg).
Blood pressure readings less than 120/80 mm Hg are considered normal. High blood pressure is defined as a reading of 140/90 or above. People with a reading between the two are said to have "pre-hypertension."
Each group drank their assigned beverages three times per day for six months.
After the six months the tea drinkers' systolic blood pressure -- the top number -- fell 2 mm Hg, and their diastolic blood pressure also fell about 2 mm Hg.
While a drop in blood pressure is generally good, a 2 mm Hg drop is not significant enough to bring a person with high blood pressure out of the danger zone.
However, the placebo group's systolic blood pressure went up about 1 mm Hg and their diastolic blood pressure also increased about 0.5 mm Hg.
To account for potential influences from other foods, researchers had the people in both groups cut back on flavonoid-rich foods such as apples, grapes, dark chocolate and wine four weeks before and throughout the study.
According to the researchers, the findings might provide a bigger benefit if they are applied to a large group.
SOURCE: Archives of Internal Medicine, online January 23, 2012.
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