Dark Chocolate, But Not Tea, Takes a Bite Out of Blood Pressure

MONDAY, April 9 (HealthDay News) -- Cocoa-rich products such as dark chocolate may help lower high blood pressure, but tea won't do much, according to a new survey of the medical literature by German researchers.

Although the thought of chocolate as a health food has captured public attention, not much research on the issue has been done, said a team from the University Hospital of Cologne.

Their report covered exactly 10 studies on cocoa with a total of 173 participants and five tea studies with 343 participants.

The benefits are believed to come from compounds known as polyphenols (or flavonoids), explained Dr. Dirk Taubert, senior lecturer in pharmacology and toxicology at Cologne and lead author of the report.

He leavened his support of chocolate with a bit of caution.

"Based on our analysis, regular consumption of polyphenol-rich cocoa products like dark chocolate may be considered a part of a blood pressure-lowering diet, provided there is no total gain in calorie intake," Taubert said. "However, in the studies we reviewed, the blood pressure results occurred with cocoa doses above the habitual intake and were observed only in the setting of short-term interventions."

In other words, for the average chocolate nibbler, the jury is still out on the sweet's health effects, Taubert said. "To date, it is not known whether long-term intake of small habitual amounts of cocoa, such as a small bar or piece of chocolate per day, may also cause significant blood pressure effects," he said.

The cocoa studies lasted an average of two weeks, with four out of five trials reporting a reduction in both systolic blood pressure (the top number in a blood pressure reading, when the heart contracts) and diastolic number, when the heart relaxes.

The average reduction was 4 to 5 millimeters of mercury (mm/Hg) in systolic pressure and 2 to 3 millimeters in diastolic pressure -- enough to reduce the risk of stroke by 20 percent and of coronary heart disease by 10 percent.

No such reduction in blood pressure was noted in any of the tea trials, which lasted an average of four weeks.

Tea and cocoa contain different kinds of polyphenols -- flavan-3-ols in tea, procyanids in cocoa, the researchers said.

"We do not know exactly which are the active blood pressure-lowering ingredients in cocoa," Taubert said. "There is evidence that the cocoa polyphenols are responsible, but there are several hundreds of phenols in cocoa."