Chocolade
verlaagt de bloeddruk.*
Het
eten van pure chocolade is waarschijnlijk net zo effectief om de bloeddruk te
verlagen, als het nemen van bloeddrukverlagende medicijnen. Thee blijkt veel
minder effectief te zijn. Dat blijkt uit een Duitse studie.
Hierbij hebben de onderzoekers gegevens uit belangrijke onderzoeken
gecombineerd. Het gaat om vier onderzoeken naar zwarte thee, één naar groene
thee en vijf naar pure chocolade. Uit vier van de vijf onderzoeken naar pure
chocolade, blijkt dat de bloeddruk na het eten van pure chocolade verminderd.
Het effect van het eten van 85 gram pure chocolade per dag, blijkt hetzelfde als
het nemen van bloeddrukverlagende medicijnen als Tenormin. Uit de andere
onderzoeken blijkt dat thee niet hetzelfde effect heeft. De onderzoekers zeggen
wel dat de onderzoeken kort waren. Het is daardoor niet duidelijk wat de
effecten zijn op lange termijn.
Cocoa,
But Not Tea, May Lower Blood Pressure
Foods rich in cocoa appear to reduce blood
pressure but drinking tea may not, according to an analysis of previously
published research in the April 9 issue of Archives of Internal Medicine,
one of the JAMA/Archives journals.
Current guidelines advise individuals with hypertension (high blood pressure) to
eat more fruits and vegetables, according to background information in the
article. Compounds known as polyphenols or flavonoids in fruits and vegetables
are thought to contribute to their beneficial effects on blood pressure and
cardiovascular risk. "Tea and cocoa products account for the major
proportion of total polyphenol intake in Western countries," the authors
write. "However, cocoa and tea are currently not implemented in
cardioprotective or anti-hypertensive dietary advice, although both have been
associated with lower incidences of cardiovascular events."
Dirk Taubert, M.D., Ph.D., and colleagues at the University Hospital of Cologne,
Germany, conducted a meta-analysis of 10 previously published trials, five of
cocoa's effects on blood pressure and five involving tea. All results were
published between 1966 and 2006, involved at least 10 adults and lasted a
minimum of seven days. The studies were either randomized trials, in which some
participants were randomly assigned to cocoa or tea groups and some to control
groups, or used a crossover design, in which participants' blood pressure was
assessed before and after consuming cocoa products or tea.
The five cocoa studies involved 173 participants, including 87 assigned to
consume cocoa and 86 controls, 34 percent of whom had hypertension (high blood
pressure). They were followed for a median (middle) duration of two weeks. Four
of the five trials reported a reduction in both systolic (the top number, when
the heart contracts) and diastolic (the bottom number, when the heart relaxes)
blood pressure. Compared with those who were not consuming cocoa, systolic blood
pressure was an average of 4.7 millimeters of mercury lower and diastolic blood
pressure was an average of 2.8 millimeters of mercury lower.
The effects are comparable to those achieved with blood pressure-lowering
medications, the authors note. "At the population level, a reduction of 4
to 5 millimeters of mercury in systolic blood pressure and 2 to 3 millimeters of
mercury in diastolic blood pressure would be expected to substantially reduce
the risk of stroke (by about 20 percent), coronary heart disease (by 10 percent)
and all-cause mortality (by 8 percent)," they write.
Of the 343 individuals in the five tea studies, 171 drank tea and 172 served as
controls, for a median duration of four weeks. Drinking tea was not associated
with a reduction in blood pressure in any of the trials.
Tea and cocoa are both rich in polyphenols, but while black and green tea
contain more compounds known as flavan-3-ols, cocoa contains more of another
type of polyphenol, procyanids. "This suggests that the different plant
phenols must be differentiated with respect to their blood pressure-lowering
potential and thus cardiovascular disease prevention, supposing that the tea
phenols are less active than cocoa phenols," the authors write.
The findings do not indicate a widespread recommendation for higher cocoa intake
to decrease blood pressure, but it appears reasonable to substitute phenol-rich
cocoa products such as dark chocolate for other high-calorie or high-fat
desserts or dairy products, they continue. "We believe that any dietary
advice must account for the high sugar, fat and calorie intake with most cocoa
products," the authors conclude. "Rationally applied, cocoa products
might be considered part of dietary approaches to lower hypertension risk."
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http://archinte.ama-assn.org/cgi/content/short/167/7/626
(Arch Intern Med. 2007;167:626-634.) (Mei 2007) (Opm. Meer over chocolade.)