People who couldn't stomach a medical study requiring them to give up chocolate ended up helping science, anyway.

These chocoholics' blood platelets displayed a reduced tendency to clot together in dangerous clumps, researchers found.

Billed as the "first biochemical analysis" on the subject, the finding may explain why chocolate can be good for the heart.

"Chocolate that's flavonoid-rich, that's dark, that's good quality, that's not traveling with all of its bad friends like sugar and fat, probably has some fairly potent pro-health benefits, although not as strong as aspirin," said lead researcher Diane Becker, professor of medicine at Johns Hopkins University School of Medicine in Baltimore.

Her belief: "Not all chocolate is bad."

Becker presented the findings at the annual meeting of the American Heart Association, in Chicago.

Another expert cautioned that chocolate is just one sweet piece of the dietary puzzle, however.

The study is "interesting and in the right direction but the overall diet is what people ought to be concerned about," said Dr. Robert H. Eckel, professor of medicine at the University of Colorado School of Medicine in Denver and past president of the AHA. He was not involved in this research.

Previous laboratory research had already shown this effect with large quantities of dark chocolate, which has high levels of antioxidants called flavonoids.

"The quantities were far more than anyone would ever eat and the measurements were done only two to four hours after the people consumed it," Becker, a self-professed chocoholic, explained. "We didn't know about chocolate consumption the way people really eat it."

The 139 individuals participating in this "offshoot" study had already been disqualified from a larger study examining the effects of aspirin on blood platelets. All had a family history of premature coronary heart disease, putting them at higher risk for heart disease.

Participants were instructed to follow a strict exercise regimen and to refrain from smoking or consuming food or drinks known to affect the activity of blood platelets, which are key to clotting. In addition to coffee, tea and other caffeinated drinks, this meant chocolate.

The "chocolate offenders" admitted to eating chocolate on the sly, however. Rather than just disqualifying them, the study authors decided to use their cheating ways for an additional analysis. Becker and her team tested platelet samples from the "offenders" and from a control group to see how long it took for platelets to clump together.

Chocolate appeared to slow clotting. On average, platelets in the chocoholics took 130 seconds to stick together, and in the control group about 123 seconds.

A test of urine for the waste products of platelet activity found that chocolate eaters also had less activity and produced fewer waste products.

"People who ate chocolate had markedly lower amounts of urinary excretion of this byproduct of platelet activity, which meant that the platelets are not being activated and not clumping so much in the body," Becker said. "The magnitude of the difference is very significant."

"What you eat in everyday life in relatively small quantities, as long ago as 12 hours, affects platelet function -- which is kind of a way to express the amount of time it takes for blood to clot," she continued. "It makes blood less sticky and less likely to clot and less likely to be part of a process that could cause a heart attack."

The bottom line? A little high-quality chocolate once in a while probably won't kill you. But follow nutritionists' advice, too -- don't ingest pounds of the stuff because the sugar and fat may kill you.