Rich in antioxidants, chocolate may be more than a sinful sweet.

Over the last few years, evidence has been piling up in support of chocolate, touting its ability to decrease the risk of heart disease, improve blood flow and lower body mass index (BMI). Recent scientific studies by Yale professors suggest that limited doses of chocolate may confer significant health benefits.

“I do think it is a health food, I think it’s a food you can love that loves you back and I think if you get the dose right, you can get the pleasure of eating chocolate and the health benefits,” said David Katz, associate professor of public health at the Yale School of Medicine and director of the Yale Prevention Research Center.

Katz has focused his research largely on chocolate’s cardiovascular effects. He conducted several intervention studies looking at solid dark chocolate and liquid cocoa and studied their effect on the endothelium, an inner lining of blood vessels that determines blood flow, as well as on blood pressure and lipid levels. Chocolate, he discovered, had a “potent” beneficial effect on blood flow, noticeable both immediately and over a span of six weeks.

The long term effects of chocolate are not yet clear, he added.

Within chocolate, it appears that the miracle workers may be compounds called flavonoids, said Mary Savoye, research dietician at Yale University’s Pediatric Clinic. Flavonoids, also present to a larger extent in many vegetables, contribute to chocolate’s bitter taste and are found in chocolates with higher cocoa concentrations.

“All chocolates are not created equal,” Savoye said.

When combined with other foods, such as milk, chocolate loses much of its health benefits, Savoye said. Chocolate cake, therefore, is far less healthy than a dark chocolate bar. Dutch processing, a chemical alkalizing process to smooth flavor, destroys many nutrients as well, Katz added.

Currently, Katz is conducting another trial to discover the therapeutic dose of chocolate. He estimates that roughly an ounce a day of dark chocolate that is at least 60 percent cocoa is probably optimal.

“I think it’s really quite convincing that eating the right kind of chocolate in reasonable doses at regular frequencies confers a meaningful net health benefit,” Katz said.

Outside of the heart, chocolate has also been proven to have favorable metabolic effects. Last week, Beatrice Golomb, associate professor of medicine at the University of California, San Diego, published a study in the Archives of Internal Medicine suggesting that chocolate may assist in weight loss. After surveying over 1,000 adults about their weekly food intake, Golomb discovered that more frequent chocolate consumption was correlated with lower BMI, a a relationship not explained by any other health factors. The chocolate-eaters did not exercise more frequently or eat more fruits and vegetables, in fact, they ate more calories than other subjects. Despite that, they weighed less, she said.

“There are reasonable prospects for this association to be causal, but I would fall short on generating recommendations based on this,” Golomb said. “What I would say for people who eat modest amounts of chocolate regularly is that they can feel less guilty about it.”

The study did not inquire about type or amount of chocolate consumed, though Golomb added that eating excessive amounts of chocolate is probably not a good idea.

Golomb said her interest in studying chocolate began at a heart association meeting. She was sitting next to a chocolate researcher, who looked at the confection for dessert forlornly and bemoaned the number of calories in chocolate. Golomb “opined” that perhaps chocolate’s metabolic benefits might offset its calories.

“She looked at me thoughtfully for about a minute, nodded and then we both tucked in,” Golomb said.

Savoye said the next frontier of chocolate research is neurological. Showing people images of chocolates and other high calorie food images triggers the reward regions of the brain, which releases dopamine, said Rajita Sinha, director of the Yale Stress Center. Chocolate also contains endocannabinoids, compounds found also in marijuana that reduce pain, and various reports suggest it may be an aphrodisiac.

Chocolate is not the first food to prove itself to be healthy, against conventional wisdom.

Several years ago, Katz said, Americans were “fat-phobic” and shied away from nuts. But now, nutritionists realize that nuts are concentrated sources of calories that are extremely nutritious and contain healthy fats. Similarly, eggs were off the menu for years because they were seen to raise cholesterol. Katz said this is almost certainly wrong.

When researching the net health effects of particular foods, it is important to also consider how people’s diets would change with the food’s inclusion or exclusion, Katz said. When eggs were excluded, for example, people turned instead to unhealthy donuts, bagels and Danish as breakfast alternatives. He said the same thing holds true for chocolate: eating chocolate instead of potato chips would be a good thing, but eating chocolate instead of broccoli would be a bad thing.

There are plenty of chocolates on the market that can satisfy consumers’ cravings and diets, Katz said. He recommends Ghirardelli’s 60 percent cacao dark chocolate bars for their short ingredient list and high cacao concentration. New products are available that go a step further, such as raw cocoa beans themselves.

“I joke to my patients that chocolate is my favorite vegetable, and it’s only half a joke,” Golomb said. “It is a plant-based food. We tend to forget because it’s usually eaten as a sweet and we think of sweets as purely bad for people. But things look favorable from the chocolate and health standpoint.”

According to other studies, chocolate can defend skin against UV damage, quiet coughs and improve vision.