article

June 5, 2008

Hot Cocoa Can Improve Artery Health in Patients With Type 2 Diabetes

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.

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).

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.

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 important in the prevention of diabetes

and its complications.

The investigators performed two studies: a 10-patient feasibility study

to determine the appropriate dosing, to assess 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 report 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 support of this hypothesis,

Balzer and colleagues report 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.

In an editorial accompanying the study, Dr. Umberto Campia (Washington

Hospital Center, Washington, 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.

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 assessing

relevant clinical

outcomes are necessary before any recommendations are made regarding

dietary supplementation with flavanol-rich cocoa, " they write.

Journal of the American College of Cardiology, June 3, 2008. J Am Coll

Cardiol 2008; 51:2141-2149 Balzer J, Rassaf T, Heiss C, et al. Sustained

benefits

in vascular function through flavanol-containing cocoa in medicated

diabetic patients.

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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