Chocolate lovers who couldn't give up the treats in the name of science showed less clotting in narrow blood vessels than those who did not eat chocolate, researchers have found.

The results do not mean it's OK to binge on chocolate, a snack high in fat and sugar, say the researchers.

Diane Becker of the Johns Hopkins University's School of Medicine and her colleagues set out to test the effects of ASA (acetylsalicylic acid) on blood platelets — cells involved in blood clots.

Participants were asked not to eat certain foods, such as chocolate, that affect platelets 24 hours before coming in for testing. But 139 of the 1,200 participants broke the rules of the study, which was conducted from June 2004 to November 2005.

"Eating a little bit of chocolate or having a drink of hot cocoa as part of a regular diet is probably good for personal health, so long as people don't eat too much of it, and too much of the kind with lots of butter and sugar," said Becker.

The findings suggest that eating as little as two tablespoons a day of dark chocolate, the purest form, has a biochemical effect similar to ASA in reducing platelet clumping.

The "chocolate offenders" received their "fix" from a variety of sources, including chocolate bars, cups of hot cocoa and ice cream.

Platelet samples from the compliant participants and the offenders were run through a mechanical blood vessel system to time how long it takes the platelets to clump in a thin tube.

On average, platelets from the chocolate lovers took 120 seconds to react, compared with 123 seconds in the other group. Participants ranged in age from 21 to 80.

Of lesser magnitude

The effect is nowhere near the magnitude of that of ASA, said Becker, who presented the results on Tuesday at the American Heart Association meeting in Chicago.

Urine tests also showed the chocolate eaters had lower levels of waste products of platelet activity.

"We have to be careful to emphasize that one single healthy dietary practice cannot be taken alone, but must be balanced with exercise and other healthy lifestyle practices that impact the heart," said study co-author Dr. Nauder Faraday, a professor at Johns Hopkins.

The researchers plan to continue the study of people with a family history of heart disease, to see if chocolate lovers show different rates of heart attacks, strokes or heart surgery.