Researchers in this featured study sought to assess the clinical efficacy of low habitual consumption of polyphenol-rich cacao. They note that while fruits and vegetables have received much attention in the literature for their plant polyphenols and associated clinical significance, cacao products are not yet incorporated into current dietary treatment strategies. Investigators point out that cacao is rich in flavonals, a subclass of polyphenols which are thought to account for their favorable cardiovascular effects. However, they note that former cacao studies demonstrating a reduction in blood pressure (BP) and improved endothelial function were observed in trials with high doses of chocolate over a short time period. Moreover, no data is available as to the potential downside of habitual high-dose consumption of cacao liquor due to the fat and sugar content. In this study, investigators sought to determine if cacao given in low, regular doses would warrant recommendation as an effective antihypertensive dietary strategy. They also sought to confirm their hypothesis that the main causative factor for BP reduction is cacao phenol stimulated nitric oxide synthesis via S-nitrosoglutathione.
This study was a randomized, controlled, investigator-blinded trial involving two groups of unpaid volunteers in Duisburg, Germany, ages 55-75. Volunteers included individuals of both sexes in good health and/or subjects in the upper-range of prehypertension or stage 1 hypertension. Investigators controlled for many potentially confounding factors (no hypertensive medication, no supplements or regular consumption of chocolate products, etc) and excluded participants with a number of cardiovascular related diseases, disorders, surgeries and several other complications, states/conditions. Forty-four volunteers (24 women, 20 men) were randomly assigned to a dark or white chocolate group, and required to consume either a 6.3-g dose of polyphenol-rich dark chocolate - containing 3.1 g of cacao (30 mg of polyphenols) - or a 5.6 g dose of polyphenol-free white chocolate. All participants completed this 18-week trial, which included BP and plasma assessments at baseline, 6, 12 and 18 weeks. Regular activities were maintained and participants tracked nutrient intake via a daily food diary/questionnaire.
Observations of both group outcomes revealed a progressive improvement in systolic and diastolic BP in the dark chocolate group with no changes in the white chocolate group. In addition to a clinically significant reduction in BP over time, researchers observed a corresponding increase in plasma levels of vasodialative Snitrosoglutathione in the dark chocolate group. At 18 weeks, the dark chocolate group reduction in mean systolic BP was -2.9 (1.6 mm Hg) and diastolic BP dropped by -1.9 (1.0 mm Hg). Notably, researchers discovered that this small amount of cacao results in a similar BP reduction when compared with comprehensive dietary modifications. Given the ease of adopting a low amount consumption of flavonol-rich cacao into the daily diet, Taubert et al suggest this "may be a promising behavioral approach to lower blood pressure in individuals with above-optimal blood pressure." The results of this study are “clinically noteworthy” assert researchers, as a "3-mm Hg reduction in systolic BP would reduce the relative risk of stroke mortality by 8%, of coronary artery disease mortality by 5%, and of allcause mortality by 4%."
Study:Taubert, D, et al, JAMA, 298 (1): 49-60, (2007)