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Nibble of Chocolate May Lower Blood Pressure |
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Written by Stephen Daniells
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Thursday, 05 July 2007 |
04/07/2007 - Having a morsel of chocolate every day may lower blood pressure levels
and lead to clinically important reductions for cardiovascular diseases,
suggests a new study.
Results of
the randomised, controlled, parallel-group trial, published in the Archives
of Internal Medicine, involved 44 adults with pre- (BP 130/85 - 139/89) or
stage one hypertension (BP 140/90 - 160/100), suggest that a daily serving of
dark chocolate
containing 30 calories associated with a lowering of blood
pressure.
Hypertension, defined as having a systolic and diastolic BP
greater than 140 and 90 mmHg, affects about 600 million people worldwide and is
associated with over seven million deaths.
"The most intriguing
finding of this study is that small amounts of commercial cocoa confectionary
convey a similar BP-lowering potential compared with comprehensive dietary
modifications that have proven efficacy to reduce cardiovascular event
rate," wrote lead author Dirk Taubert from University Hospital of
Cologne.
"Whereas long-term adherence to complex behavioural changes
is often low and requires continuous counselling, adoption of small amounts of
flavanol-rich cocoa into the habitual diet is a dietary modification that is
easy to adhere to and therefore may be a promising behavioural approach to lower
blood pressure in individuals with above-optimal blood pressure," he
added.
The researchers randomly assigned the volunteers to a daily either
portion of 6.3 g (30 kcal) of dark chocolate containing 30 mg of polyphenols
(Ritter Sport Halbbitter, Alfred Ritter) or matching polyphenol-free white
chocolate (Milka Weisse Schokolade, Kraft Foods) for 18 weeks.
At the end
of the study, the researchers observed that consumption of the dark chocolate
led to reductions in both systolic and diastolic BP by 2.9 and 1.9 mm Hg,
respectively, without affecting body weight, blood lipid levels, or blood sugar
(glucose) levels).
"Although the magnitude of the BP reduction was
small, the effects are clinically noteworthy," wrote the researchers.
"On a population basis, it has been estimated that a 3-mm Hg reduction in
systolic BP would reduce the relative risk of stroke mortality by eight per
cent, of coronary artery disease mortality by five per cent, and of all-cause
mortality by four per cent.
"Furthermore, the blood
pressure reductions in our randomized trial are in the same range that were
reportedly associated with habitual cocoa intake (a median of 4.2 g per day) in
an epidemiological study involving elderly men."
No change in blood
pressure was observed as a result of eating the polyphenol-free white
chocolate.
The prevalence of hypertension in the population declined from
86 to 68 per cent.
Consumption of the polyphenol-rich dark chocolate led
to measurable increases in blood polyphenol concentrations, and the blood
pressure reduction was accompanied by a sustained increase of
S-nitrosoglutathione, linking the effects to Nitric Oxide production in the
cardiovascular system.
"The apparent mechanism by which dark
chocolate lowered BP suggests a chronic increase in the production of nitric
oxide in the vascular endothelium. The unstable Nitric Oxide reacts with thiol
groups to form stable S-nitrosothiols that have been suggested to contribute to
BP regulation," said the researchers.
"Future studies should
evaluate the effects of dark chocolate in other populations and evaluate
long-term outcomes," the authors conclude.
The British Heart
Foundation's nutritionist Sara Stanner told the BBC: "It is important to
remember that chocolate is also high in fat and calories so over-indulgence is
not good for your heart.
"Fruits and vegetables
provide a range of polyphenols, as well as important vitamins and minerals.
Eating five or more portions of fruit and vegetables a day is therefore the best
way to protect your heart - and you don't need to worry about
over-indulging."
The study was funded by the University Hospital of
Cologne, Germany
Source: Journal of American Medical
Association
2007, Volume 298, Number 1, Pages 49-60
"Effects of
Low Habitual Cocoa Intake on Blood Pressure and Bioactive Nitric Oxide - A
Randomized Controlled Trial"
Authors: D. Taubert, R. Roesen, C. Lehmann,
N. Jung, E. Schomig
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