A fter working below the radar on a cocoa farm deep in Brazil, and toiling for years over test tubes in food labs, scientists say they have developed a top-secret formula for an undisciplined candy lover's dream: a healthful chocolate bar.

Eating a couple of tiny slabs a day of this dark chocolate could lower cholesterol, relax your blood vessels and help ward off heart disease, they say.

Loaded with potent chemicals such as cocoa flavanols, plant sterols and soy - and stamped with an icon that reads, "promotes a healthy heart" - the CocoaVia line of chocolates has been available in select American department stores and by next month will be in mainstream grocery stores.

Don't look for these bars in the candy section: Possibly the first chocolates explicitly marketed as health foods, they will be over in the health aisle.

Mars, which makes CocoaVia, says this is only the beginning. "There is a next generation of products in the pipeline," says Harold Schmitz, chief scientist for Mars, speaking from one of its chocolate factories in Elizabethtown, Pennsylvania, where he had just lunched on a CocoaVia bar plucked off the production line.

"We are investigating dozens and dozens of product formats. We are considering all possibilities."

But some nutritionists roll their eyes at the notion that eating chocolate - even if it is made with a special patented recipe and supplemented with healthful ingredients - is the best way to promote cardiovascular health.

"If someone is addicted to chocolate, this may be a better choice than other chocolate bars," says Mark Kantor, associate professor of nutrition at the University of Maryland. "But to think that you are going to lower blood cholesterol levels, or chance of heart disease, by eating two of these a day - that is just wishful thinking."

CocoaVia chocolate bars are made from a patented powder known as Cocoapro cocoa. Cocoa in its raw state is one of the best known sources of plant flavanols: a naturally occurring compound in plants found to a lesser extent in red wine, green tea and certain vegetables.

Cocoapro, Schmitz says, is a flavanol powerhouse, manufactured to be of consistently high quality, often containing many times more than other, run- of-the-mill cocoas.

A growing body of evidence suggests that these flavanols found in cocoa are good for you.

In the early 1990s, Harvard University Professor Dr Norman Hollenberg (who later collaborated with Mars on cocoa research) found that a population of island-dwelling Kuna Indians of Panama, who consume three to four cups of cocoa a day, had lower blood pressure, less hypertension and fewer cardiovascular diseases than their relatives who moved to the mainland and dropped their cocoa consumption.

And this month, Dutch researchers reported in the Archives of Internal Medicine that older men who consumed a lot of cocoa had a 50 percent lower risk of dying from any disease than those who ate none over the course of the 15-year study.

A review of 136 scientific articles on chocolate and its ingredients published between 1996 and 2005 found that eating small amounts of dark chocolate reduces the risk of dying of heart disease by about 19 percent, according to an analysis that appeared January in the journal Nutrition and Metabolism.

One hundred milligrams of flavanols daily appear to have beneficial effects, such as lowering blood pressure and improving insulin sensitivity, says Eric Ding, a graduate student at the Harvard School of Public Health who conducted the analysis.

"In the short term, there is a large body of evidence that supports the beneficial effects of chocolate and flavanols," he says. But, he adds, "no one has done any long-term, randomized trials" - carefully controlled experiments where people are given flavanolrich chocolate, or not, and had their heart health tracked over years.

Scientists say no food company is ever likely to perform such a pricey and time-intensive study on chocolate.

CocoaVia bars cost a little more than US$1 (HK$7.80) each - slightly more if purchased online - and are a little larger than a single Twix bar. They contain between 90 and 100 calories (depending on whether you opt for the original chocolate bar or the one with the soy crisps) and no trans fats.

Each contains more than 100 milligrams of flavanols: Eat two a day, advises the company, and you will get enough to promote heart health.

The bars also contain between 1.1 and 1.5 grams each of plant sterols, cholesterol-like substances made by plants. Studies suggest that eating two grams of plant sterols a day lowers cholesterol by 10 percent, and companies are permitted to make a health claim that their product reduces cholesterol if it contains 1.3 grams of plant sterol esters per serving.

These ingredients don't sway some nutritionists.

"One can only be in awe of the creativity of chocolate marketers," says Marion Nestle, professor of nutrition, food studies and public health at New York University. "My take is that if there is a health benefit, it is small."

CocoaVia chocolates, though not as calorie-laden as some candy bars, are not calorie-free. Without trimming 200 calories somewhere else, or walking an additional 45 minutes each day, one could end up gaining about 10 kilograms over a year, wrote Harvard nutritionists in a February article about CocoaVia.

"If somebody decides to consume plant sterols because they have elevated cholesterol levels, it might be better to try to find a non-caloric source," says Alice Lichtenstein, professor of nutrition at Tufts University's Friedman School of Nutrition who heads the American Heart Association's nutrition committee.

Other candy companies are aware of the possible cardiovascular benefits of cocoa and the marketing opportunity they provide, though none have yet gone as far as Mars.

Hershey's is rapidly expanding its dark chocolate offerings. (Most researchers agree the more cocoa in a product, the more flavanols it has.) Last year, it acquired the San Francisco-based premium dark chocolate company Scharffen Berger, and last September introduced Hershey's Extra Dark.

Spokeswoman Stephanie Moritz says a study at Yale University recently showed that eating Hershey's Extra Dark "can result in short-term improvement in arterial function and blood pressure."

Tricia Bowles, a spokeswoman for Nestle, says that soon the company will launch "Treasures," with packaging that "will call out the benefit of antioxidants." But, she added, "These products are not marketed or sold as `health food,' but rather as a treat."

LOS ANGELES TIMES