The cocoa bean, actually a seed, grows in pods on trees. It contains compounds called flavanols, which have been shown to lower blood pressure, improve blood flow and reduce overall risk of heart disease. Three scientific analyses published in the past six months pooled results of smaller studies to conclude that cocoa is good for the heart. Scientists believe flavanols work, at least in part, by stimulating production of nitric oxide, which relaxes vessels and improves blood flow.

The catch, says David L. Katz, director of Yale University's Prevention Research Center, is that exactly how much chocolate is needed for a health benefit isn't known. 'Chocolate is a concentrated source of calories, so it's important to keep the dose within therapeutic range,' he says.

Most chocolate isn't labeled with milligrams of flavanols and there's no industry or scientific standard yet for measuring flavanols in chocolate. One objective measure is the cocoa percentage on the label. Milk chocolate can be as little as 10% cocoa paste by weight, with the rest in sugar, milk and other ingredients. Dark-chocolate bars typically contain 50% to 60% cocoa by weight, scientists say.

'The higher the percentage of cocoa, the higher the flavanol content, the higher the antioxidant content and thus we believe the greater positive health benefit,' says Washington, D.C., nutritionist Joy Dubost, a spokeswoman for the Academy of Nutrition and Dietetics, a trade group.

A growing number of specialty products are offering higher-test cocoa, as much as 100%, which makers say are minimally processed to retain as many nutrients as possible. Most of the brands don't have lab tests on the amount of flavanols, so there's no way to make a comparison.

Antidote 'red label' chocolate contains nothing but high-quality cocoa beans from Ecuador, says Red R. Thalhammer, owner of Tripple Red Corp., the Long Island City, N.Y., company that sells it. A bar is 440 calories. To drink your flavanols, Choffy is specially milled 100% cocoa and roasted to taste good when brewed like coffee─ideally in a French press, says Jason Sherwood, co-founder of Choffy LLC, Vancouver, Wash. It is $15 for a 12-ounce bag and 20 calories for an eight-ounce cup.

Or take your chocolate straight and chomp on raw cocoa beans. Navitas Naturals, sold by Navitas LLC, Novato, Calif., offers crunchy whole beans or nibs─beans with the shell removed─at $10 for an eight-ounce bag. To maintain maximum nutrients, the nibs aren't roasted, Navitas says. Unsweetened nibs are 130 calories an ounce; sweetened, 150 calories.

Navitas Naturals, Choffy and Antidote haven't done clinical trials on their products.

As for taste, the products overall were mostly intense and delicious, though it sometimes took a few bites to adjust to chocolate without sugar. Choffy was so delicious, I drank it without milk and sugar. Navitas's unsweetened nibs were a bit intense and the sweetened ones were a bit too sweet; a half-and-half mixture of the two was just right.

Then there's cocoa as a dietary supplement. CocoaWell dietary supplement pills from Reserveage Organics LLC, Gainesville, Fla., are filled with cocoa powder and other plant antioxidants. According to the bottle's label, every two pills contain at least 450 milligrams of pure plant flavanols. CocoaWell costs $30 for a month's supply. There are no clinical trials on CocoaWell yet.

Mars Inc. packs 350 milligrams of cocoa flavanols into its 30-calorie a day CocoVia daily supplements. To keep the flavanol content high, Mars 'gently' processes its cocoa' and adds an extract of cocoa flavanols made with a proprietary process, says Catherine Kwik-Uribe, director of research and development at the Mars Botanical unit. Mars also sells Cirku, a 15-calorie packet containing cocoa extract with a fruit flavor that you mix with water. Mars found heart-health benefits with a research blend of gently processed cocoa that is similar to CocoaVia but without the extract added. It doesn't yet have results on CocoaVia and Cirku.

Some cardiologists say even the spate of recent research doesn't provide enough evidence for taking chocolate as a dietary supplement. 'I don't think it's overwhelming evidence,' says Carl Lavie, medical director of Cardiac Rehabilitation and Prevention at Ochsner Medical Center in New Orleans. Other nutrients─including Vitamin E─have looked just as promising and later proved disappointments, he adds. It isn't unreasonable to eat chocolate for health reasons if you enjoy the taste, he adds, but make sure to cut a snack of equivalent calories from your diet.

There is some evidence that suggests as little as a few ounces of chocolate─including types found in many grocery stores─may be beneficial. A 45-person study published in 2010 co-authored by Dr. Katz found blood flow in vessels improved two hours after ingesting a 2.6-ounce serving of Hershey's HSY +0.30% Extra Dark (327 calories). The study was funded by Hershey's and the Centers for Disease Control and Prevention.

Four tablespoons a day of Hershey's unsweetened cocoa (about 40 calories) in a variety of research test beverages also has been shown to be heart-healthy, according to the study and at least one other published trial. Hershey's Extra Dark contains 420 milligrams of flavanols in a 1.4-ounce serving and Hershey's cocoa contains 210 milligrams of flavanols per tablespoon, says Debra Miller, director of nutrition at Hershey Co.'s Center for Health and Nutrition.

According to research by Hershey Co., dutch processing, a chemical alkalizing process that makes chocolate less bitter, also destroys many nutrients. Consumers can choose regular cocoa instead of the dutch-processed variety. Also, Hershey's research has shown that baking a chocolate cake with baking soda, which is an alkaline, destroyed flavanols but nutrients were retained when using baking powder.