SCIENCE NEWS, 3/18/00, vol. 18, p. 188-189

CHOCOLATE HEARTS - YUMMY AND GOOD MEDICINE

More than 35 million heart-shaped boxes of chocolate changed hands in the United States on Valentine's Day this year. The holiday's total chocolate sales approached $1 billion. Yet this confection's link to hearts is extending beyond the lucrative candy business.

Chocolate and cocoa powders are derived from beams that contain hefty quantities of natural antioxidants called flavonoids. In recent years, research has correlated consumption of tea, red wine, and other foods rich in these compounds with a reduced risk of cardiovascular disease. Realizing that this observation might transform chocolate's reputation from junk food into health-promoting snack candy companies and the American Cocoa Research Institute (ACRI) in McLean, Va., have begun pumping money into studies of chocolate's antioxidants.

Those investments now hint at big payoffs. New findings - many reported for the first time last month in Washington, D.C., at the annual meeting of the American Association for the Advancement of Science (AAAS) - suggest that chocolate's chemistry confers cardiovascular benefits.

Though preliminary, the research indicates that cocoa and chocolates not only contain natural compounds that can protect the heart and blood vessels but also that the quantities present in commercial products may be sufficient to exert measurable effects.

These studies are prompting manufacturers to reevaluate how they make chocolate, since some techniques unintentionally eliminate flavonoids. Mars, Inc., recently developed a proprietary process to preserve flavonoids. By next month, the company plans to be labeling U.S. products made with the process, which they call Cocoapro. Then, observes Harold H. Schmitz, Mars' director of nutrition and analytical services in Hackettstown, N.J., consumers can identify chocolates retaining much of a cocoa bean's initial flavonoid riches.

A 40-gram serving of milk chocolate typically contains around 400 milligrams of antioxidants, about the same quantity as a glass of red wine, according to research published last year by Joe A. Vinson of the University of Scranton (Pa.). Dark chocolate aficionados will be happy to learn that a serving of their favorite contains more than twice that quantity - roughly the same amount as a cup of black tea. Unsweetened powdered cocoa starts out with almost twice as much of these antioxidants as dark chocolate. But to make a cup of hot chocolate, the cocoa is diluted with water or milk and sugar, so the flavonoid total per serving plummets to about half of that present in milk chocolate.

At least as important as the total amount of flavonoids, however, is the potency of these antioxidants, Vinson notes. And the potency of those in chocolate is impressive, his team reported in the December 1999 JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY.

Vinson and his colleagues found that, matched molecule for molecule, chocolate's flavonoids are more powerful than vitamins such as ascorbic acid in limiting the oxidation of cholesterol circulating in low-density lipoproteins (LDLs) and very-low-density lipoproteins. Arteriosclerosis studies have suggested that oxidation of these lipoproteins is an essential step in the creation of artery-clogging plaque.

Vinson, whose work was supported by ACRI, doesn't know which chocolate products the institute gave him to test or the complex mix of flavonoids within them.

Yet individual flavonoids - some 4,000 have been identified in plant products so far - vary not only in potency but also in mode of action. The primary family of flavonoids contributing to the antioxidant prowess of chocolates is the procyanidins, notes Schmitz. Their basic unit is a three ring molecular structure. The mature cocoa bean contains pairs known as dimers, triads known as trimers, quartets known as tetramers, and larger ensembles of these units.

Test-tube studies by German scientists recently showed that chocolate's tetramers were the top performers among this group in curbing the type of oxidation that free radicals can wreak in blood vessel walls. That's potentially important, Schmitz notes, because such naturally occurring radicals can inflame vessels, a process that fosters a dangerous rupturing of arteriosclerotic plaque (SN: 2/6 99, p. 86).

Chocolate's tetramers and larger procyanidins also help relax the inner surface of blood vessels according to studies in isolated tissues headed by C. Tissa Kappagoda of the University of California, Davis School of Medicine.

This relaxation "is a major player in vascular health," he explains. People in whom it's absent or grossly impaired often have high blood pressure, arteriosclerosis, or other symptoms of cardiovascular disease.

In healthy blood vessels, Kappagoda noted at the AAAS meeting, much of this relaxation is controlled by the production of nitric oxide (SIN 3/23/96, p. 180). His research, funded by Mars, indicates that chocolate's compounds exert their relaxing effect by increasing nitric oxide concentrations.

Test-tube studies by Schmitz's team at Mars dovetail with the findings by both groups. Chocolate procyanidins can dampen the activity of enzymes that trigger inflammation and ratchet up production of nitric oxide, Schmitz reported at the meeting. Moreover he notes, both of these actions may be independent of the flavonoids' antioxidant role.

Yet Cesar G. Fraga of the University of Buenos Aires hails the procyanidins' antioxidant activity. In work funded by Mars, he has demonstrated a rise of chocolate-derived procyanidins in the blood of men and women who had just eaten semi-sweet chocolate candies. His team found that blood sampled 2 hours after candy consumption protected its circulating lipids from oxidation. The more chocolate eaten, the better the protection.

Earlier test-tube studies, he says, indicate that the procyanidins may function as a first line of defense against damaging oxidants - sparing vitamin C and other antioxidant vitamins that would otherwise be destroyed in the battle. In these experiments, while all of the tested procyanidins appeared active, the pentamer offered the best protection.

Nutritionist Carl L. Keen, Fraga's collaborator at UC Davis, has conducted additional Mars-funded work. At the AAAS meeting, he unveiled data from new studies indicating that flavonoid rich foods may benefit the heart yet another way, by damping the reactivity of blood platelets.

When stimulated by any of several chemical triggers, these cells turn sticky, helping blood to clot. Doctors often recommend that people at risk of heart attacks take aspirins to reduce clotting. Keen's data now show that chocolate's procyanidins work like especially mild aspirins.

His group gave water, procyanidin-rich cocoa, or alcohol-free red wine to groups of 10 men and women. The researchers sampled and tested the volunteers' blood 2 and 6 hours later.

Though both the wine and cocoa significantly delayed the blood's clotting time, only the cocoa protected blood platelets from fragmentation. Platelets tend to fragment when they become overly sticky, Keen says.

At the Experimental Biology meeting in San Diego next month, Penny Kris-Etherton and her colleagues at Pennsylvania State University in State College, who are funded by ACRI, plan to report yet another cardiovascular benefit. In the 24 volunteers whom they studied, diets enriched with dark chocolate or cocoa powder raised the individuals' high-density lipoprotein (HDL) cholesterol, the so-called good cholesterol.

"This is important," Kris-Etherton says, "because a higher ratio of HDLs to LDLs is associated with a decreased risk of heart disease."

Why should consumers trust the tantalizing data on chocolate if they're all coming from industry-funded research? 'That's a valid question," acknowledges nutritionist John W. Erdman of the University of Illinois at Urbana-Champaign who co-chaired the AAAS symposium on chocolate. Though he believes people should be skeptical, he also points out that these studies would never get off the ground without candy industry financing.

Erdman likens the situation to Quaker Oats' funding of research that laid the foundation for studies that proved oats' ability to lower serum cholesterol. Similarly, soy producers funded most of the initial work showing that proteins and antioxidants in their crops could fight heart disease. When it comes to potential neutraceuticals - foods offering health benefits - publication of a critical mass of promising, peer-reviewed, industry-financed studies appears necessary before the government will step in with financial support, Erdman says.

While U.S. chocolate makers would love to be able to adorn their labels with health claims, Schmitz says that "a lot of research needs to be done before we get to that point."

If that ever happens, chocolate will have come full circle, says Louis E. Grivetti, a nutritional historian at UC Davis. His research team is documenting extensive medicinal use of chocolate and cocoa that dates back at least 500 years throughout Europe and the Americas. Healers used them to treat dozens of conditions, including tuberculosis, anemia, gastrointestinal upset, and kidney stones.

Concludes Norman K. Hollenberg of Harvard Medical School in Boston who co-chaired the AAAS symposium, "the issue [today] isn't should we or should we not be recommending chocolate. The fact is, we are eating chocolate" - more than 12 pounds per person in the United States each year. The new data suggest that unless we overindulge, says Hollenberg, "people should not feel guilty about eating it."