Dark chocolate and other foods derived from the cacao bean (Theobroma cacao
) are rich in flavonoid polyphenols such as procyanidins.7
The Olmec and Aztec Mesoamericans used cacao to treat pain and inflammation.
An impressive relationship between cacao intake, BP, cardiovascular outcomes, and mortality was first demonstrated in the Dutch Zutphen Elderly Study. When 470 elderly men were followed prospectively for 15 years, those with the highest cocoa consumption had lower BP—and an adjusted 50% relative reduction in risk of cardiovascular and all-cause mortality.8
This is confirmed by several small trials. A recent meta-analysis of 5 randomized controlled trials (N = 173) measured BP before and after daily consumption of chocolate. Patients consumed an average of 100 g daily (500 mg of polyphenols) for approximately 2 weeks. There was a reduction in systolic BP of 4.7 ± 2.9 mm Hg (P
< .002) and in diastolic BP of 2.8 ± 2.0 mm Hg (P
The meta-analysis was statistically rigorous; 2 authors reviewed each of the studies and their methodologic quality (Jadad scale score of 8 to 10 out of 13). A funnel plot showed no publication bias, sensitivity analysis identified 1 study with undue influence, and Cochran Q testing uncovered some interstudy heterogeneity. The authors did not report concurrent methods of BP measurement or medication use. Blood pressure reduction was seen in 2 trials of hypertensive patients and in 2 of 3 trials of normotensive subjects.
The authors subsequently found long-term BP reduction from regular consumption of smaller amounts of chocolate.10
They randomized 44 hypertensive patients to receive a 6.3 g square of dark chocolate or white chocolate daily for 18 weeks; those who ate dark chocolate had a reduction in systolic BP of 2.9 ± 1.6 mm Hg (P
< .001) and in diastolic BP of 1.9 ± 1.0 mm Hg (P
This study was also important because the authors found a substantial rise in serum levels of S-nitrosoglutathione, which reflects levels of nitric oxide. This supports other evidence that suggests flavonoids in cacao upregulate nitric oxide synthase in endothelial cells11
and that chocolate improves endothelial function.12
It seems reasonable to recommend that people with hypertension eat 10 to 30 g of dark chocolate daily. Recent data suggesting that dark chocolate also improves vascular function in diabetic patients should alleviate concern in this population.13
Because most commercial chocolate bars are processed under conditions that destroy flavonoids, so-called gourmet
chocolate containing at least 70% cacao is a better choice. One potential risk is the triggering of migraine headaches in some patients.