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Chocolate "offenders" teach science a sweet lesson

Study helps explain heart benefits from daily - but small - dose
of chocolate

From the Johns Hopkins University School of Medicine and
Bloomberg School of Public Health

January 24, 2007

COLLEGE PARK, Md., (AScribe Newswire)— Some "chocoholics"
who just couldn't give up their favorite treat to comply
with a study to test blood stickiness have inadvertently
done their fellow chocolate lovers - and science - a big

Their "offense," say researchers at Johns Hopkins led to
what is believed to be the first biochemical analysis to
explain why just a few squares of chocolate a day can almost
halve the risk of heart attack death in some men and women
by decreasing the tendency of platelets to clot in narrow
blood vessels.

"What these chocolate 'offenders' taught us is that the
chemical in cocoa beans has a biochemical effect similar to
aspirin in reducing platelet clumping, which can be fatal if
a clot forms and blocks a blood vessel, causing a heart
attack," says Diane Becker, M.P.H., Sc.D., a professor at
The Johns Hopkins University School of Medicine and
Bloomberg School of Public Health.

Becker cautions that her work is not intended as a
prescription to gobble up large amounts of chocolate candy,
which often contains diet-busting amounts of sugar, butter
and cream. But as little as 2 tablespoons a day of dark
chocolate - the purest form of the candy, made from the
dried extract of roasted cocoa beans - may be just what the
doctor ordered.

Researchers have known for nearly two decades that dark
chocolate, rich in chemicals called flavonoids, lowers blood
pressure and has other beneficial effects on blood flow.
The latest Hopkins findings, to be presented Nov. 14 at the
American Heart Association's annual Scientific Sessions in
Chicago, identified the effect of normal, everyday doses of
chocolate found in ordinary foods, unlike previous studies
that found decreased platelet activity only at impractically
high doses of flavonoids equivalent to eating several pounds
of chocolate a day.

"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,"
says Becker.

In the study, 139 people Becker - whom Becker somewhat
tongue in cheek calls "chocolate offenders" - were
disqualified from a much larger study looking at the effects
of aspirin on blood platelets. The Genetic Study of Aspirin
Responsiveness (GeneSTAR) was conducted at Hopkins from June
2004 to November 2005 and enrolled more than 500 men and 700
women participants nationwide.

Shortly before aspirin dosing began for the subjects,
they were told to stay on a strict regimen of exercise and
to refrain from smoking or using foods and drinks known to
affect platelet activity. These included caffeinated
drinks, wine, grapefruit juice - and chocolate.

The non-compliers - who admitted to eating chocolate -
were a diverse group who got their flavonoid "fix" from a
variety of sources, including chocolate bars, cups of hot
cocoa, grapes, black or green tea, and strawberries. And
while they were excluded from the aspirin study, Becker and
her team scoured their blood results for chocolate's effect
on blood platelets, which the body recycles on a daily

When platelet samples from both groups were run through a
mechanical blood vessel system designed to time how long it
takes for the platelets to clump together in a hair-thin
plastic tube, the chocolate lovers were found to be less
reactive, on average taking 130 seconds to occlude the
system. Platelets from those who stayed away from chocolate
as instructed clotted faster, at 123 seconds.

In another key test of urine for waste products of
platelet activity, primarily urinary thromboxane
(11-dehydro-thromboxane B2), scientists found that chocolate
eaters showed less activity and waste products on average,
at 177 nanograms per millimol of creatinine, versus an
average of 287 nanograms per millimol of creatinine in the
group that abstained.

Participants ranged in age from 21 to 80; 31 percent were
black and the rest were white. In total, more than 200
different tests of platelet reactivity were performed and
analyzed in the study. Because whole blood contains other
cells that affect platelet aggregation, testing was repeated
using a purified version of test samples made up of strictly
platelet-rich plasma.

None of the "offenders" had previous histories of heart
problems, such as a heart attack, but all were considered to
be at slightly increased risk of heart disease because of
family history. Fifty percent of women participants were

"These results really bring home the point that a modest
dietary practice can have a huge impact on blood and
potentially on the health of people at a mildly elevated
risk of heart disease," says study co-author Nauder Faraday,
M.D., an associate professor at Hopkins. "But we have to
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."

Besides Becker and Faraday, other investigators in this
research were Lisa Yanek, M.P.H.; Taryn Moy, M.S.; and Lewis
Becker, M.D.

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