News:Cocoa Containing Flavanols might be Beneficial in Diabetic Patients with Vascular Dysfunction

May 29, 2008 By Vijayalakshmi Kunadian MBBS MD MRCP [mailto:vkunadian@perfuse.org]

Endothelial dysfunction is a major determinant of atherosclerosis and has been demonstrated to be associated with adverse cardiovascular outcomes among diabetic patients with cardiovascular risk factors and among those with established cardiovascular diseases. Previous studies have suggested beneficial effects of flavanol-containing cocoa products on platelet aggregation, insulin sensitivity, endothelial function, blood pressure and low density lipoprotein oxidation and have been correlated with mortality due to cardiovascular disease and diabetes mellitus. Fruit, vegetables, tea, red wine, cocoa and cocoa products are rich in flavanols. Nitric oxide (NO) is essential factor for endothelial function which can be measured by flow-mediated dilation (FMD). Although the exact mechanism of the beneficial effect of flavanols is unclear, flavanols have been speculated to work by an increase in the NO synthase activity.

A new study by Balzer and co-workers published in the latest issue of the Journal of the American College of Cardiology [see link below] determined the longer-term (30 days) effects of flavanol-containing cocoa on vascular function among diabetic patients. The investigators conducted a feasibility study consisting of 10 patients and an efficacy study consisting of 41 patients. Both studies were randomized, double-blinded and controlled. Patients aged 50-80 years with stable type 2 diabetes mellitus for at least 5 years were included in the study. Those in the feasibility study consumed a cocoa drink (Hackettstown, New Jersey) that provided 3 doses of flavanols (control: 75 mg flavanol, medium: 371 mg flavanol, and high: 963 mg of flavanol). In the efficacy study 2 doses of flavanols were administered for 30 days (treatment group: 321 mg flavanol/dose, 3 doses/day and the control group: 25 mg flavanol/dose, 3 doses/day). FMD of the brachial artery, plasma flavanol metabolites, arterial blood pressure, and heart rate were measured in the 2 studies at regular intervals.

In the feasibility study, there was a significant increase in the FMD at 2 hours following ingestion of the highest dose flavanol (963 mg) compared with baseline FMD values (5.5±0.4% vs. 3.8±0.3%, p<0.001) and plasma flavanol concentration.

In the efficacy study, daily intake of flavanol-containing drink resulted in a continual increase in the FMD from 3.3±1.1% at baseline, to 4.1±1.1% at day 8 and 4.3±1.2% at day 30, p<0.0001. There was no evidence of desensitization and tachyphylaxis (drug tolerance). No difference in the FMD was observed among those who received sublingual nitrate between the treatment and the study groups. Significant rise in the plasma flavanol levels was observed among those who consumed the highest dose of flavanol-containing drink (p<0.01). Blood pressure, heart rate and glycemic control were unaffected. No side effects were observed during the entire duration of the study.

The investigators provide 4 main conclusions for their study in diabetic patients:
 * Flavanols are absorbed in a dose dependent fashion
 * Regular daily ingestion of flavanol-containing cocoa reverses vascular function
 * Vasodilation using GTN is unaffected by flavanol consumption
 * Consumption of flavanol was well tolerated without major adverse effects.

This study along with previous studies underscores the importance of dietary intervention in the management of patients with diabetes and provides insight to the treatment of vascular dysfunction. Further research to determine the impact of flavanol-containing drinks on clinical outcomes among diabetic patients with cardiovascular disease would be worthwhile.