The researchers -- who included David L. Katz, MD, MPH, of the Yale Prevention Research Center -- gave some of the participants a dark chocolate bar containing 22 grams of cocoa. Other participants got a bar containing no cocoa.
Before-and-after blood pressure and ultrasound tests showed better blood pressure and better blood vessel function after participants ate the dark chocolate bar, compared to the cocoa-free bar.
Likewise, blood pressure and blood vessel function improved after participants drank two cups of cocoa, compared with drinking a beverage containing no cocoa.
How the cocoa drink was sweetened mattered. When it contained sugar, blood pressure and blood vessel function didn't improve as much as when the cocoa was sugar-free.
Katz and colleagues reason that in the sugary cocoa drink -- which contained about 45 grams of sugar per serving -- the sugar may have offset cocoa's effects to some degree.
The study -- published in the July 1 edition of The American Journal of Clinical Nutrition -- was partly sponsored by the Hershey Company.
Of course, eating too much chocolate or drinking too much cocoa isn't a great idea. Blow your calorie budget and extra pounds will pile up, which is bad for your blood pressure.