Reference
Desch S, Kobler D, Schmidt J, et al. Low vs. higher-dose dark chocolate and blood pressure in cardiovascular high-risk patients. Am J Hypertens. 2010 Mar 4. [Epub ahead of print]
Design
Prospective, randomized, open-label, blinded, end-point design trial.
Participants
102 patients with prehypertension/stage 1 hypertension and established cardiovascular end-organ damage or diabetes mellitus.
Study Medication and Dosage
Patients were randomly assigned to receive either 6 or 25 grams/day of flavanol-rich dark chocolate for 3 months.
Main Outcome Measures
The difference in 24-hour mean blood pressure between groups.
Key Findings
Both groups, those consuming either 6 or 25 grams/day of chocolate, had statistically significant reductions in mean ambulatory 24-hour blood pressure (6 grams/day: -2.3 mm Hg, 95% CI: -4.1 to -0.4; 25 grams/day: -1.9 mm Hg, 95% CI: -3.6 to -0.2). There were no significant differences in blood pressure changes between the 2 groups.
Practice Implications
This is just one of a series of recent papers suggesting that chocolate may have cardioprotective effects. Part of the theory to explain this effect is that the flavanols present in chocolate trigger nitric oxide synthases that increase nitric oxide production in the blood. Nitric oxide is a potent vasodilator and improves endothelial function. The authors of this clinical trial had previously published a meta-analysis of earlier studies of the impact of high-flavanol chocolates on blood pressure. Analyzing data combined from 10 trials comprising 294 individuals, they had calculated a mean decrease of -4.5 mm Hg (95% CI: -5.9 to -3.2; P<0.001) for systolic blood pressure and -2.5 mm Hg (95% CI: -3.9 to -1.2; P<0.001) for diastolic blood pressure.1 The actual mechanisms underlying the benefits are likely more complex.
The flavanols in chocolate also exert anti-inflammatory effects. In a study of 42 people at high risk for atherosclerosis who consumed 40 grams of cocoa powder per day for 4 weeks, significant reductions were measured in the expression of VLA-4, CD40, and CD36 in monocytes. Serum levels of the endothelium-derived adhesion molecules P-selectin and intercellular adhesion molecule-1 were also significantly lower.2
A 2008 study gave 28 healthy individuals daily chocolate doses to provide 700 mg of flavonoids/day. After one week, low-density lipoprotein fell by 6% and high-density lipoprotein rose by 9%.
Eating the chocolate reduced highly sensitive C-reactive protein levels in women.
Eating the chocolate reduced highly sensitive C-reactive protein levels in women.3
We soon may have one more tool in our bag for helping patients reduce elevated blood pressure. The above paper was unable to demonstrate a dose-dependent difference in effect between consumption of 6 grams and 25 grams per day; we do not have the wanted scientific justification to tell patients, “With chocolate, more is better.” Rather it appears that this particular benefit plateaus at a low dose. This may be advantageous as higher doses may cause unwanted weight gain.
Note: The chocolates used in this study are not currently sold over-the-counter in the United States.
