Chocolade
tegen dichtslibben bloedvaten.*
Meer
dan honderd chocoladeverslaafden hebben de medische wetenschap een grote dienst
bewezen. Doordat ze zich niet hielden aan een voorgeschreven dieet, hebben
Amerikaanse onderzoekers ontdekt dat chocolade voorkomt dat aderen dichtslibben.
Dat verkleind het risico op hart- en vaatziekten aanzienlijk.
De wetenschappers deden onderzoek naar het effect
van de pijnstiller aspirine op bloedplaatjes. Om te voorkomen dat de test werd
beďnvloed door bepaalde eetgewoontes, mochten de 1.200 deelnemers niet roken,
geen cafeďne houdende dranken, wijn en grapefruitsap drinken en ook de
chocolade moesten ze laten staan. Dat laatste was voor 139 deelnemers teveel
gevraagd. Ze zondigden waardoor de onderzoekers de effecten van chocolade
ontdekten.
Chocolade blijkt er net als aspirine voor te
zorgen dat bloed minder makkelijk stolt, waardoor het risico
dat aderen vertopt raken verkleind wordt. Chocolade werkt net zo goed als bloedverdunner als
aspirine. Doch het is oppassen met chocolade. De meeste chocolade bevat veel vet
en suikers. Belangrijk is dus matig gebruik van alleen de beste donkere
chocolade.
CHOCOLATE
“OFFENDERS” TEACH SCIENCE A SWEET LESSON
-- Study helps explain heart benefits from daily - but
small - dose of chocolate
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 favor.
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 basis.
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 postmenopausal.
“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.
(Presentation title: Casual chocolate consumption and platelet activity.) (Nov. 2006) (Opm. Meer over chocolade.)