If it tastes good it must be bad, so the saying goes, but delicious dark chocolate may be the exception to the rule.

In addition to all the pleasurable sensations associated with the sweet, it may also help lower blood pressure by an average of 10 percent while improving the body's sensitivity to insulin, researchers report.

However, this benefit applies only to dark chocolate, which is rich in flavonoids -- the same antioxidant compounds found in fruits, vegetables and whole grains that are known to help lower blood pressure, according to the report in the July 18 online edition of Hypertension.

"It turns out that chocolate is not only a pleasurable food, but it fits in quite nicely with the other healthy recommendations," said coauthor Jeffrey B. Blumberg, a professor of nutrition and a senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. "We found that three ounces of dark chocolate per day over several weeks reduced blood pressure in patients with essential hypertension and also seemed to provide a benefit on their insulin sensitivity," he added.

In their study, Blumberg's team had 10 men and 10 women eat 3.5 ounces of dark chocolate every day for 15 days. All of these people had high blood pressure and none were taking blood pressure medications.

First, the researchers had five of the men and five of the women eat dark chocolate while the others ate white chocolate, which contains no flavonoids. Then after another week of no chocolate, the groups "crossed over" and ate the other chocolate.

In the 15 days they were eating dark chocolate, individuals displayed an average 11.9 mm Hg drop in their systolic blood pressure (the top number in a blood pressure reading) and a 8.5 mm Hg drop in diastolic blood pressure (the lower number). However, there was no drop in blood pressure when they ate flavonoid-free white chocolate, the researchers found.

Given these results, Blumberg believes that dark chocolate can be good for you. "Dark chocolate can be included as part of a healthful diet in patients who have hypertension," he said.

However, he cautioned that you can't just add it on top of your diet. "It's still a high-calorie food. You don't want to have excess calories or put on weight if you have hypertension," Blumberg said. "But as part of a healthful diet, it is something that you can enjoy and not feel you are violating the principles of a healthful diet."

Blumberg thinks that being able to enjoy some chocolate can also make it easier to stay on a healthy diet that is rich in fruits, vegetables and whole grains.

One expert sees this study as part of a body of evidence that shows that chocolate is good for us. "Dark chocolate may be health-promoting," said Dr. David L. Katz, an associate clinical professor of public health and director of the Prevention Research Center at Yale University School of Medicine.

Katz, who is doing his own research into the benefits of chocolate, noted that chocolate is rich in not only antioxidants, but also magnesium and fiber. "The predominant saturated fat in dark chocolate, stearic acid, does not raise cholesterol or harm blood vessels," he added.

"Milk chocolate and white chocolate do not offer any known health benefits, and provide more calories, sugar, and potentially harmful oils than dark chocolate," Katz said, but "dark chocolate may well prove to be health food."

According to Katz, there are many unanswered questions about chocolate: What is the optimal dose of dark chocolate? How high does the cocoa content need to be to offer health benefits? Who in the population stands to benefit from eating dark chocolate? Are the benefits of liquid cocoa and solid chocolate the same? Can people eat chocolate without gaining weight?

"These answers, and others, will come in time," Katz said. "For now, it's clear that not all chocolate is created equal. But it's delicious to think that indulgence and health may both reside beneath the same wrapper."

Another expert is more cautious. Without more definitive data on whether chocolate promotes weight gain that might outweigh its benefits, Dr. Jeffrey Mechanick, the director of the Metabolic Support Service at Mount Sinai School of Medicine, is hesitant to recommend it as a health food. "I would never tell a heart patient or a diabetic to eat more dark chocolate," he said.

For patients who do not have these health problems, Mechanick is more lenient. "Having a treat every once in a while is fine," he said. "My preference is that you have dark chocolate, because it's looking like maybe dark chocolate may have some benefit. But there are no data to support that it's truly beneficial. It's still unproven that it's beneficial and there could be risks involved."

Mechanick also warned that the data about the benefits of dark chocolate should not mean replacing other high blood pressure therapy with chocolate. "Chocolate is not an alternative to traditional lifestyle changes or to taking medications to reduce risk of heart disease or to treat diabetes," he said.