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A Mug of Hot Cocoa Can Improve Artery Health in Patients With Type 2
Diabetes
Michael O'Riordan
Heartwire 2008. © 2008 Medscape
May 27, 2008 The benefits of cocoa, known recently for its ability
to reduce blood pressure and improve endothelial function, also
extends to diabetic patients, a new study has shown [1]. In a small,
randomized study, investigators showed that the consumption of a big
mug of hot cocoa can reverse vascular dysfunction in patients with
diabetes, suggesting a therapeutic potential of cocoa in this patient
population.
"Our study clearly established improvements of endothelial function
after regular consumption of flavanol-containing cocoa in patients
with type 2 diabetes, highlighting the potential of
flavanol-containing diets and underscoring the potential health
benefit for reducing the risk of cardiovascular events in diabetic
patients," write lead investigator Dr Jan Balzer (University Hospital
RWTH, Aachen, Germany) and colleagues in the June 3, 2008 issue of the
Journal of the American College of Cardiology.
The findings are just the latest in a string of studies showing the
cardiovascular promise of foods like cocoa that contain flavanols.
Flavanols are a subgroup of plant-derived phytochemicals known as
flavonoids, and several studies have shown that flavanol-containing
foods, including cocoa, certain fruits and vegetables, tea, and red
wine, have beneficial effects on LDL oxidation, platelet aggregation,
insulin sensitivity, endothelial function, and blood pressure.
Effect of Flavanols in Diabetics Unknown
Despite the existing data, however, studies on the effects of
flavanols on the vasculature in diabetic patients were missing.
Patients with type 2 diabetes, writes Balzer and colleagues, might
receive particular benefit from flavanol-containing cocoa, because
various observational studies have shown that lifestyle modifications
are particularly im****tant in the prevention of diabetes and its
complications.
The investigators performed two studies: a 10-patient feasibility
study to determine the appropriate dosing, to *****s safety and
tolerability, and to measure the effect size of the intervention to
calculate sample size of the efficacy study. In total, 44 patients
with treated type 2 diabetes were enrolled in the randomized,
double-blind, parallel-group efficacy study, with half allocated to
the treatment arm of 321 mg of flavanols per dose three times daily.
The control patients also received some flavanols, albeit a much
smaller amount, about 25 mg per dose three times daily.
Baseline flow-mediated dilation (FMD) values were 3.3% in both the
treatment and control arms at the start of the intervention. The daily
consumption of flavanol-containing cocoa by patients in the treatment
arm resulted in continual increases in FMD, increasing from 3.3% at
baseline to 4.1% on day 8 and to 4.3% by study completion on day 30.
The investigators note that the acute effects of drinking cocoa in the
treatment arm, those recorded two hours after ingestion, were of a
similar effect size at study entry, day 8, and day 30, suggesting that
patients did not become desensitized or immune to the effects of
drinking cocoa.
On day 30, the investigators re****t that the composite maximum
increase in FMD--a combination of the chronic and acute effects of
cocoa ingestion--was 5.8%, suggesting "a reversal of endothelial
dysfunction." This reversal in endothelial dysfunction with cocoa is
comparable to intermediate- and long-term interventions using exercise
and various medications, including insulin, pioglitazone, ACE
inhibitors, and statins, write Balzer and colleagues.
The high-flavanol cocoa used in this study--which provides much more
flavanol than the typical US dietary intake of 20 to 100 mg daily--is
not sold in the supermarket.
The present study was not designed to determine the precise molecular
mechanism by which flavanols improve endothelial function. However,
the investigators point out that FMD of the brachial artery is almost
entirely dependent on nitric oxide (NO) and that endothelial function
measured by FMD is commonly used as a marker of endothelial NO
synthesis.
This proposed mechanism, they note, would make sense considering that
recurrent and prolonged hyperglycemia in diabetic patients reduces NO
bioavailability, which leads to endothelial dysfunction. In sup****t of
this hypothesis, Balzer and colleagues re****t no improvement in
endothelium-independent vasodilation after the administration of
nitroglycerin, which suggests that improvements in vascular function
are secondary to the effects of treatment on endothelial function and
NO bioavailability.
A Promising New Dietary Intervention for Type 2 Diabetes
In an editorial accompanying the study, Drs Umberto Campia and Julio A
Panza (Wa****ngton Hospital Center, Wa****ngton, DC) note that interest
in the cardiovascular benefits of cocoa started with observations of
the Kuna Indians [2]. This indigenous population in Panama consumes a
large amount of cocoa rich in flavanols and, despite a diet that also
has a large amount of salt, they have a very low prevalence of heart
disease, stroke, diabetes, and cancer compared with Kuna Indians
living in Panama City.
Campia and Panza write that because the endothelium plays a
significant role in hypertension and atherosclerosis, research efforts
have focused on the acute and chronic effects of cocoa, as well as
other drinks and food, in the hope that their consumption could
improve vascular function.
One im****tant question, the editorialists note, that this study
answers pertains to previous concerns that nutrients in the diet of
diabetic patients might not reach needed physiological levels due to
secondary impairments in gastrointestinal function. That absorption
concern is apparently unwarranted, as these data suggest flavanol
intake in diabetics results in plasma levels consistent with those
observed in nondiabetic patients. Second, this study also shows that
FMD increased steadily and was maintained over time, "suggesting a
lack of significant desensitization or tolerance."
The study, according to Campia and Pana, extends the understanding of
the vascular effects of flavanols to diabetic patients, but more work
is still needed. "Although endothelial function has been shown to
predict future cardiovascular events, randomized, large-scale clinical
trials *****sing relevant clinical outcomes are necessary before any
recommendations are made regarding dietary supplementation with
flavanol-rich cocoa," they write.
Mars Inc provided the instant cocoa powder used in the preparation of
cocoa drinks in the study. Dr Hagen Schroeter, one of the paper's
authors, is employed by Mars Inc.
Balzer J, Rassaf T, Heiss C, et al. Sustained benefits in vascular
function through flavanol-containing cocoa in medicated diabetic
patients. J Am Coll Cardiol 2008; 51:2141-2149.
Campia U and Panza JA. Flavanol-rich cocoa: A promising new dietary
intervention to reduce cardiovascular risk in type 2 diabetes? J Am
Coll Cardiol 2008; 51:2150-2152.
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