Prescription Strength Chocolate, Revisited

For roughly a decade, science-savvy chocolate consumers have taken comfort from a string of studies suggesting that their sweet and usually high-fat vice has a potential up side. The most reassuring news was that the antioxidant flavonoids abundant in dark chocolate appear to reduce blood pressure and perhaps protect people from dangerous blood clots.

Raw cocoa beans, shown here nestled in their pods, contain huge amounts of heart-healthy flavanols. Commercially processing the beans to make cocoa powder strips away most of those compounds. Mars, however, determined how to retain them to make flavanol-rich cocoa for research trials—and for what it’s now marketing as a heart-healthy snack. USDA

At the Cocoa Symposium, convened at the National Academy of Sciences in Washington, D.C., earlier this month, researchers reported new findings on chocolate’s biological impacts. The studies focus on specific flavonoids in chocolate, such as epicatechin, that offer the strongest cardiovascular benefits. The bad news: Most commercial products—even dark chocolates—retain few if any of these natural, plant-based chemicals.

However, the new data do suggest how chocolatiers might tailor their candy recipes to preserve—and potentially even augment—concentrations of beneficial flavonoids. The new studies also might provide some reasons that diets rich in fruits and vegetables are good for people’s hearts.

“Cocoa is a fruit,” notes chemist Harold H. Schmitz, chief science officer for Mars Inc., the world’s largest chocolate manufacturer. Those flavonoids in cocoa that appear to confer the strongest cardiovascular benefits are found in plenty of other dietary sources as well, including tea and apples. Indeed, he says, any of these plant products might yield bioactive compounds that could fight heart disease.

Debunking cocoa myths

At the Cocoa Symposium, researchers presented data to shatter a pair of longstanding “myths,” Schmitz observes. The first is that the heart-healthy components of cocoa are antioxidants that quash naturally destructive molecular fragments in the body. The second misperception is that a person can get cocoa’s heart-protecting constituents simply by downing nearly any off-the-shelf dark chocolate.

Early work by scientists at Mars and elsewhere fostered both perceptions, Schmitz admits. For instance, studies had traced at least some cardiovascular benefits to a class of flavonoids known as flavanols and their polymers called procyanidins (SN: 3/18/00, p. 188). Key among the chocolate flavanols linked to heart benefits was epicatechin, a known antioxidant. Dark chocolates—including those that are the main ingredients in Mars’ Dove Dark bar and the mini M&M baking bits—were identified as being rich in these constituents.

However, University of California researchers Hagen Schroeter and Christian Heiss presented data at the symposium indicating that at least some of the flavanols’ benefits trace to functions other than fighting oxidation. For instance, standard commercially processed cocoa powder has little or no flavanol content, but it retains a high concentration of other antioxidants. This cocoa offered almost no cardiovascular benefits in tests with isolated tissues or people consuming the cocoa.

Moreover, notes Schroeter, even in people consuming flavanol-rich cocoa products, “most of the flavanols present in [blood] have been altered by the body following consumption and are known to have even less antioxidant potential than their parent [compounds].”

Schroeter’s group teamed up with Norman K. Hollenberg, Schmitz, and others to look at how cocoa’s epicatechin works. At the meeting, Hollenberg described finding that this flavanol and its breakdown products enhance production of nitric oxide (NO). In the body, NO dilates blood vessels, relaxes arteries, and enhances blood flow.

In one trial, the researchers administered cocoa drinks to 10 people and monitored the effects on blood flow. On one occasion, each person got a cocoa drink that was virtually devoid of flavanols. Another time, each volunteer drank a cocoa that tasted the same but was rich in these flavanols. Neither the participants nor the people taking the blood-flow readings knew which cocoa had been administered.

Only the flavanol-rich drink produced substantial blood-flow benefits, the researchers report in the Jan. 24 Proceedings of the National Academy of Sciences (PNAS). The fact that the benefits, which lasted several hours, were prevented by administering a drug that shuts down NO production “unambiguously showed that cocoa flavanols turned on NO synthesis and improved blood flow,” Schmitz says.

He adds that the study exposes the fallacy of judging chocolate’s flavanol content by measuring its cocoa-solids content. Both drinks administered in this trial were prepared with the same share of cocoa solids, Schmitz points out.

Lessons from the Kuna

In the PNAS paper and at the Cocoa Symposium, Hollenberg reviewed data he’s gleaned from studying two genetically similar populations of Kuna Indians, people renowned for their cocoa consumption. One group of the Kuna lives on the San Blas islands off Panama. The other consists of migrants residing on the mainland in Panama City.

In earlier work, Hollenberg reported that the island-dwelling Kuna had significantly lower blood pressure than their mainland kin did (SN: 3/2/02, p. 142: Available to subscribers at More good news about chocolate). One difference between the populations: The islanders drank an average of 5 cups of cocoa daily, but the mainland group downed fewer than 4 cups per week.

Schmitz notes that the two populations also drank different cocoas. Traditionally, island-dwelling Kuna take fresh-picked cocoa beans and dry them under the sun. Then, they grind the beans into a powder for use in foods and drinks. “Effectively,” he says, “they’re consuming about as close to fresh cocoa as one can get.” By contrast, the islanders’ mainland kin now tend to drink commercial cocoas that have been as heavily processed as U.S. cocoas. The products also retain as little of the starting flavanols as most U.S. products do.

Hollenberg’s follow-up work, reported in the PNAS paper, confirms that the islanders also have far larger exposures to cocoa flavanols. Tests showed that flavanol-residue concentrations in urine were six times as high in the islanders as in the mainlanders.

At the Cocoa Symposium, Hollenberg reported that dramatic long-term benefits may be attributable to the islanders’ cocoa habit: Their death rate from heart disease is less than 8 percent of that in Kuna mainlanders, and cancer kills only 16 percent as many islanders. The two populations were matched for age, weight, and a number of other factors that might affect heart and cancer risks.

Hollenberg concludes that the Kuna epidemiological data, although preliminary, “indicate that a flavanol-rich diet may provide an extraordinary benefit in the reduction of the two deadliest diseases in today’s world.”

Toward healthier chocolates . . . and spin-offs

Schmitz acknowledges that “Mars, like every other chocolate business, tends to use cocoa that has been processed in the standard industry way.” The result is that most of its products end up virtually devoid of flavanols.

Like its competitors, Mars doesn’t want to tinker greatly with the recipes of its popular products. However, for much of the past decade, the company has been seeking to create a snack that would not only taste good—which pure cocoa does not—but also would pack a healthy wallop of epicatechin and related compounds. The company has recently begun marketing a relatively low-calorie, high-flavanol candy bar using a specially processed starting ingredient called CocoaPro.

In the August 2005 Journal of Hypertension, Hollenberg and Naomi D.L. Fisher of Brigham and Women’s Hospital describe the flavanol content of various chocolate products. CocoaPro powder topped the list, with nearly 5,000 milligrams of flavanols per 100 grams of cocoa. The Kuna islander’s cocoa beans contained nearly 4,000 mg/100 g, and their cocoa powder had 2,000 mg/100 g. “In stark contrast,” the researchers observe, “all of the commercially available cocoa powders or chocolate drinks that can be purchased in American supermarkets have flavonoid contents substantially less than 5 percent of [CocoaPro’s].”

Not so fast, argue Jonathan M. Hodgson and Ian B. Puddey of the University of Western Australia School of Medicine and Pharmacology. In an editorial appearing in the same Journal of Hypertension issue, they agree with Hollenberg and Fisher that a growing body of work supports the idea that diets rich in flavonoids benefit the heart. However, the Australian team adds, “The method still widely used to quantify flavonoids is crude and provides no information about the [specific] type of flavonoids present.” Moreover, they note, not all flavonoids are readily absorbed by the body. Finally, they point out that no study has yet evaluated whether increasing flavonoids in study volunteers’ diets—from chocolate, tea, wine, or any other products—will cut that population’s heart-disease incidence.

Schmitz agrees that there’s still a lot to learn. Although his team’s new PNAS paper fills in some of the gaps that Hodgson and Puddey referred to, Schmitz says that large, multiyear trials of people eating flavanol-rich products are needed. However, such studies are beyond the financial reach of a candy company, he says. He’s hoping the new data are suggestive enough to entice the National Institutes of Health or another funding organization to step in and back such clinical follow-ups.

In the meantime, while studying how to synthesize flavanols, Mars has developed a few novel compounds that might prove even more potent than epicatechin at triggering NO synthesis. Although these compounds “have zero application for us [as candy makers], they might have use in pharmaceuticals,” Schmitz told Science News Online. Indeed, he says, “if the benefits prove striking enough, we might some day license the compounds” to companies developing cardiovascular drugs.

For Carl Keen of the University of California, Davis, who has conducted some chocolate studies, there is a somewhat different spin-off. Data on the biological action of flavanols reported at the Cocoa Symposium “add new and important pieces of information that will help us understand why diets rich in fruit and vegetables promote cardiovascular health,” he says. Chocolate science is pointing to which agents in apples, grapes, and other produce might offer the most benefits—and why.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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