Eating a small piece of dark chocolate every day reduced systolic and diastolic blood pressure in a randomized, controlled study of older people who had prehypertension or stage 1 hypertension.
The “dose” was too small to adversely affect glucose metabolism or insulin sensitivity, and it did not cause weight gain, German investigators reported in the July 4 issue of the Journal of the American Medical Association.
The magnitude of the chocolate's effect was comparable with that of “comprehensive dietary modifications that have proven efficacy to reduce cardiovascular event rate.”
Moreover, whereas “long-term adherence to complex behavioral changes is often low and requires continuous counseling, [the adoption] of small amounts of flavanol-rich cocoa into the habitual diet is a dietary modification that is easy to adhere to and therefore may be a promising behavioral approach,” wrote Dr. Dirk Taubert and his associates at the University Hospital of Cologne (Germany).
The investigators studied chocolate's effect in 20 men and 24 women aged 55-75 years who were in good general health, except for having prehypertension (blood pressure of 130/85 to 139/89 mm Hg) or stage 1 hypertension (blood pressure of 140/90 to 160/100 mm Hg). The subjects were not taking any antihypertensive medications and had normal plasma lipid and plasma glucose levels.
Study participants were randomly assigned to eat a single 6.3-g dose–1 piece of a 16-piece bar weighing 100 g–of commercially available polyphenol-rich dark chocolate or a similar-sized dose of polyphenol-free white chocolate every day for 18 weeks. They were instructed to eat the candy 2 hours after their evening meal, to abstain from other cocoa products, and to maintain their usual diet and physical activity throughout the course of the clinical trial.
Both systolic and diastolic blood pressure declined steadily over time in the participants who ate dark chocolate, but not in those who ate white chocolate.
By the end of the study, systolic blood pressure had declined by a mean of 2.9 mm Hg, and diastolic pressure by a mean of 1.9 mm Hg; these differences from baseline were statistically significant.
After 18 weeks, all 22 of the subjects in the dark-chocolate group had lower blood pressure readings than at baseline, and 4 (18%) no longer qualified as hypertensive. This corresponds to a 21% relative risk reduction (JAMA 2007;298:49-60).
“Although the magnitude of the [blood pressure] reduction was small, the effects are clinically noteworthy. On a population basis, it has been estimated that 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 all-cause mortality by 4%,” the investigators noted.
“It is likely that the cocoa flavanols in dark chocolate were responsible for the observed effects” on blood pressure, the researchers wrote.
Previous research has suggested that cocoa flavonols may enhance the formation of endothelial nitric oxide, leading to vasodilation.
Study participants ate 6.3 g daily, or 1 piece of a 16-piece bar. Vivian E. Lee/Elsevier Global Medical News