If there were a medicine that could make your blood vessels more flexible, lower your blood pressure, prevent blood clots and improve insulin sensitivity, it would be phenomenally successful. The company that produced this wonder drug would likely charge an arm and a leg for it. Your doctor would prescribe it enthusiastically.

There is such a drug, but your doctor doesn't prescribe it. The drug is dark chocolate.

More than a year ago, we described a Dutch study showing that older men who ate chocolate were 50 percent less likely to die of a heart attack during the 15-year follow-up (Archives of Internal Medicine, Feb. 27, 2006).

It didn't take long for someone to object: "You are irresponsible to suggest that chocolate has health benefits. Chocolate is high in calories and full of fat and sugar. Anyone who eats chocolate should not be kidding himself that it's good for him."

This spring, newscasts reported that a review of randomized controlled clinical trials showed significant blood-pressure-lowering benefit from chocolate. Again, the naysayers responded: "A lot of press attention has been given to the benefits of dark chocolate for lowering blood pressure. But the average systolic pressure was only lowered 5 points and the diastolic pressure by about 3 points. These numbers are hardly anything to get excited about. Why are people so enthusiastic?"

While it is true that these numbers don't indicate a dramatic change, even standard blood pressure pills don't lower blood pressure much more than that. A study in the Journal of the American Medical Association (Nov. 10, 2004) found the popular medications Norvasc (amlopidine) and Vasotec (enalapril) lowered systolic pressure by 5 points and diastolic by about 2.5 points.

A new study published in the Journal of the American Medical Association (July 4, 2007) confirms that dark chocolate can indeed lower blood pressure. The difference in the new research is that it only took a little bit of chocolate.

Many previous studies ran for just a few weeks, and volunteers were given 100 grams of chocolate a day. That is quite a large chunk of chocolate. Weight gain would be a realistic concern.

The most recent study ran several months, but the volunteers got much less chocolate, just about 6 grams daily. Those 30 calories a day didn't lead any of the volunteers to gain weight, but it was enough chocolate to reduce blood pressure.

Although the reduction was modest, it was enough to be clinically noteworthy. The investigators concluded that this effect would be enough to reduce the risk of stroke, heart attack and overall mortality in a population.