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Thee voor een goede bloeddoorstroming.*
A cup of black tea may give a
quick boost to blood flow to the heart, the results of a small study suggest.
In an experiment with 10
healthy men, Japanese researchers found that blood-flow in the coronary arteries
improved two hours after the men drank black tea. The same was not true of a
caffeinated drink used for comparison.
Numerous studies have
suggested that tea drinking may do a heart good, with effects on cholesterol,
blood clotting and blood vessel function being among the proposed mechanisms.
The new study, reported in the
American Journal of Cardiology, suggests it also has a more immediate beneficial
effect. The authors suspect that black tea improved the dilation of the men's
blood vessel, allowing better blood flow.
Tea is rich in antioxidant
compounds called flavonoids, and these may be the key to the beverage's
potential heart benefits, study co-author Dr. Kenei Shimada of Osaka City
University told Reuters Health.
For the study, the researchers
used a special ultrasound method to gauge "coronary flow velocity
reserve" or CFVR. This reflects how much blood-flow can speed up when
demands are put on the heart, and paints a picture of the healthiness of the
coronary circulation.
Shimada's team measured the
CFVR of each of the men after they drank either black tea or a caffeinated
beverage, and found that it increased significantly after the black tea.
"The results of this
study suggest that black tea consumption has a beneficial effect on coronary
circulation," the researchers report.
They speculate that the
flavonoids in black tea improve the functioning of the lining of the blood
vessels, increasing how much the vessels dilate in response to blood flow.
Dysfunction in this lining, called the endothelium, is one of the things that
goes wrong as heart disease develops.
It's not clear what the
long-term implications of the findings on CFVR might be, but Shimada said
research has shown coronary flow reserve to be related to heart disease risk.
Larger studies, particularly
in people with coronary artery disease, are needed to establish how tea affects
the coronary circulation, the researchers conclude.
SOURCE: American Journal of
Cardiology, June, 2004.