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Amanda Jekowsky,
American College of Cardiology, 202-375-6645, ajekowsk@acc.org
May
26, 2008
Cocoa Could Be a Healthy Treat for Diabetic Patients
Flavanols in cocoa improve artery function,
help relieve stress on heart
For people with diabetes, sipping a mug of steaming, flavorful
cocoa may seem a guilty pleasure. But new research suggests
that indulging a craving for cocoa can actually help blood
vessels to function better and might soon be considered part
of a healthy diet for the prevention of cardiovascular disease.
Flavanols, natural plant compounds also found in tea, red
wine, and certain fruits and vegetables, are responsible for
cocoa’s healthful benefits. In fact, according to new
research published in the June 3 issue of the Journal
of the American College of Cardiology (JACC), after diabetic
patients drank specially formulated high-flavanol cocoa for
one month, blood vessel function went from severely impaired
to normal.
The improvement was as large as has been observed with exercise
and many common diabetic medications, the researchers noted.
These findings suggest that it may be time to think not just
outside the box, but inside the cup, for innovative ways to
ward off cardiovascular disease—the number one cause
of death in diabetic patients.
“Medical treatments alone often do not prevent complications
of diabetes that are associated with atherosclerosis and cardiovascular
disease,” said Malte Kelm, M.D., a professor and chairman
of cardiology, pulmonology and vascular medicine at the University
Hospital Aachen and the Technical University Aachen, in Aachen,
Germany. “Physicians should be increasingly looking
to lifestyle changes and new approaches to help in addressing
the cardiovascular risks associated with diabetes.”
For the study, Dr. Kelm and his colleagues first tested the
feasibility of using high-flavanol cocoa to improve cardiovascular
health by observing, on three separate days, the effects of
cocoa with varying amounts of flavanols on blood vessel function
in 10 patients with stable type 2 diabetes.
The second, larger part of the study tested the effectiveness
of long-term, routine consumption of high-flavanol cocoa in
comparison with low-flavanol cocoa in 41 patients with stable
type 2 diabetes. Patients were randomly assigned to drink
cocoa with either 321 mg of flavanols per serving or only
25 mg of flavanols per serving three times daily for 30 days.
The two types of cocoa tasted and looked the same, despite
differences in flavanol content. In addition, neither patients
nor investigators were aware of which type of cocoa each patient
had been assigned to drink.
Blood vessel function was tested on the first day before
the patients consumed any cocoa and again two hours after
drinking the beverage. The test was repeated before and after
cocoa consumption on day 8 and day 30.
To gauge the effect of high-flavanol cocoa on blood vessel
function, the researchers used a test called “flow-mediated
dilation” (FMD), which evaluates the ability of the
arteries to expand (dilate) in response to an increase in
the demand for blood, oxygen and nutrients. The FMD test involves
measuring the diameter of the brachial artery in the upper
arm using ultrasound, then inflating a blood pressure cuff
on the forearm for several minutes. The squeezing of the blood
pressure cuff temporarily starves the forearm muscles of blood
and oxygen, causing the body to increase blood flow to those
muscles. In healthy people, the inner lining of the arteries,
or endothelium, senses the increased blood flow and sends
a chemical signal telling the arteries to expand. In Dr. Kelm’s
laboratory, a normal FMD response among healthy people the
same age as those participating in the study is a 5.2 percent
expansion in arterial diameter, on average.
The researchers found that patients with type 2 diabetes
had a severely impaired FMD response at the beginning of the
study. Before patients consumed any cocoa, the brachial artery
expanded by only 3.3 percent, on average. Two hours after
drinking high-flavanol cocoa, the FMD response was 4.8 percent.
Over time, those findings improved, however. After patients
drank high-flavanol cocoa three times daily for eight days,
the average FMD response improved to 4.1 percent at baseline
and to 5.7 percent two hours after cocoa ingestion. By day
30, the FMD response had improved to 4.3 percent at baseline
and 5.8 percent after cocoa ingestion. All of the improvements
were highly statistically significant.
Among patients who consumed low-flavanol cocoa, there were
no significant differences in baseline FMD response over time,
or in FMD response after cocoa ingestion on days 8 and 30.
FMD measurements can provide valuable information about a
person’s cardiovascular health. Previous studies have
shown that people with an impaired FMD response have an increased
risk of heart attack, need for bypass surgery or catheter
procedure to open clogged coronary arteries, and even death
from heart disease.
Dr. Kelm speculated that cocoa flavanols improve FMD response
by increasing the production of nitric oxide, the chemical
signal that tells arteries to relax and widen in response
to increased blood flow. Relaxation of the arteries takes
stress off of the heart and blood vessels.
The high-flavanol cocoa used in this study—which provided
many times more flavanols than the typical U.S. dietary intake
of 20 to 100 mg daily—is not sold in the supermarket.
Dr. Kelm cautioned that the take-home message of the study
is not that people with diabetes should guzzle cocoa, but
rather, that dietary flavanols hold promise as a way to prevent
heart disease.
“Patients with type 2 diabetes can certainly find ways
to fit chocolate into a healthy lifestyle, but this study
is not about chocolate, and it’s not about urging those
with diabetes to eat more chocolate. This research focuses
on what’s at the true heart of the discussion on “healthy
chocolate”—it’s about cocoa flavanols, the
naturally occurring compounds in cocoa,” he said. “While
more research is needed, our results demonstrate that dietary
flavanols might have an important impact as part of a healthy
diet in the prevention of cardiovascular complications in
diabetic patients.”
Umberto Campia, M.D., who co-wrote an editorial about the
new study in the same issue of JACC, noted that diabetics
are an ideal population in which to study the effects of flavanols
on arterial function, because high blood sugar damages the
endothelium and because these patients have a high risk of
cardiovascular disease.
Any therapy that helps the lining of the arteries to function
better is potentially important, said Dr. Campia, a research
associate with MedStar Research Institute in Washington, D.C..
“The endothelium is one of the largest organs in the
body,” he said. “It maintains the health of the
arteries and prevents blockages that can cause heart attacks,
strokes and limb loss.”
“This study is important and thought-provoking,”
he noted. “We now have sizeable evidence that cocoa
flavanols have a positive effect on the health of the arteries.
This is the foundation we need for doing a much larger prospective
study that looks at the effect of cocoa flavanols not just
on endothelial function, but also on the risk of heart attack,
stroke, and other serious forms of cardiovascular disease.”
This study was supported by an unrestricted grant from Mars
Inc., McLean, VA. The company also provided the instant cocoa
beverage powders used in the study but had no role in the
design, conduct, or analysis of the study. One of the authors,
Hagen Schroeter, Ph.D., is employed by Symbioscience, a newly
established scientific division of Mars, Inc.
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optimal cardiovascular care and disease prevention. The College
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online at www.acc.org .
The American College of Cardiology (ACC) provides these news
reports of clinical studies published in the Journal of the
American College of Cardiology as a service to physicians,
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