Ten male and 10 female patients (mean age, 43.7 years) with untreated essential hypertension were randomly assigned to receive 100 g/day of flavanol-rich dark chocolate (DC; containing 88 mg of flavanols) or 90 g per day of flavanol-free white chocolate (WC) for 15 days. After a 7-day washout period, each person consumed the other type of chocolate for an additional 15 days. The diet was made isocaloric compared with baseline by reducing the intake of other foods that were similar in energy and macronutrient composition to chocolate. After DC consumption, mean 24-hour systolic blood pressure decreased by 11.9 mm Hg (p < 0.0001 comparing DC with baseline and with WC). After DC, mean diastolic blood pressure decreased by 8.5 mm Hg (p < 0.0001 comparing DC with baseline and with WC). DC but not WC significantly decreased insulin resistance (p < 0.0001), as determined by homeostasis model assessment, and significantly improved flow-mediated dilatation of the brachial artery. The mean LDL-cholesterol concentration decreased from 3.4 mmol/L to 3.0 mmol/L after DC (p < 0.05 comparing DC with baseline and with WC).
Comment: In this study, consumption of 100 g/day of dark chocolate for 15 days decreased blood pressure and serum LDL cholesterol levels, improved flow-mediated dilatation of the brachial artery (which may reduce the risk of atherosclerosis), and decreased insulin resistance in patients with essential hypertension. The results suggest that eating dark chocolate is useful for treating hypertension and might help prevent atherosclerosis and diabetes. However, the study lasted only 15 days, and it is not known whether these benefits would persist with continued use. In addition, 100 g of dark chocolate contains 531 calories, and long-term consumption of this amount of chocolate could cause obesity. While the participants in this study kept their total energy intake the same by eliminating other foods from their diet, it is likely that most people who consume that much chocolate would increase their total calorie intake.
Furthermore, chocolate contains a number of psychoactive chemicals, including phenylethylamine (an amphetamine-like compound) and anandamide (a substance that binds to the "marijuana receptor" in the brain). For many people, chocolate is not only addictive, but also causes various adverse reactions such as migraines or mood changes. Nevertheless, persons who are able to include a controlled amount dark chocolate as part of a healthful, weight-maintaining diet might benefit from such an addition. It should be noted the positive effects attributed to chocolate occur only with dark chocolate, not with white chocolate (which has only small amounts of flavonoids) or milk chocolate (milk strongly inhibits the absorption of the beneficial flavonoids).
Grassi D, et al. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension 2005;46:398-405.
