To the Editor: Chocolate may have beneficial cardiovascular effects, possibly due to cocoa polyphenols. Experiments in animals suggest that plant polyphenols decrease blood pressure; however, evidence from human clinical trials is lacking. We examined whether dark chocolate (polyphenol-rich chocolate [PRC]) may lower BP in individuals with mild isolated hypertension.
Methods
We conducted a randomized crossover trial in 13 otherwise healthy individuals (6 men and 7 women, aged 55-64 years, with body mass index of 21.9-26.2 [calculated as weight in kilograms divided by the square of height in meters]) with recently diagnosed and untreated stage 1 mild isolated systolic hypertension (mean [SD] systolic BP, 153.2 [3.9] mm Hg; mean [SD] diastolic BP, 83.8 [3.5] mm Hg). After a cocoa-free run-in phase of 7 days, participants were randomly assigned to receive 14 consecutive daily doses of either 100-g dark PRC bars containing 500 mg of polyphenols and 480 kcal of energy (Ritter Sport Halbbitter, Alfred Ritter, Waldenbuch, Germany), or 14 days of 90-g white chocolate (polyphenol-free chocolate [PFC]) bars that also contained 480 kcal and similar amounts of cocoa butter, macronutrients, fiber, electrolytes, and vitamins (Milka Weisse Schokolade, Kraft Foods, Bremen, Germany). After a cocoa-free washout phase of 7 days, participants were crossed over to the other condition. Participants were asked to substitute the chocolate bars for foods of similar energy and macronutrient composition. Overall diet during the study period was assessed by reports of daily food intake and by measurement of body weight, plasma concentrations of lipids and glucose, and urinary excretion of sodium, potassium, and nitrogen at the run-in phase and after each intervention period.
The BP was recorded daily, in a blinded fashion, with participants in a seated position, 12 hours post-dose, in the left upper arm with a validated oscillometer (Omron HEM 722C, Omron, Mannheim, Germany). A systolic BP of more than 170 mm Hg or a diastolic BP of more than 100 mm Hg at a single visit was necessary for referral for antihypertensive pharmacological treatment. At the end of the study participants were referred to their physician for further monitoring and management of BP. We received approval for our study from the ethics committee of the Medical Faculty of the University of Cologne; all participants gave written informed consent.
Results
Participants had significantly lower systolic and diastolic BPs within 10 days of beginning PRC, but this effect was not seen during the PFC period. At the end of the 14-day PRC intervention, mean (SD) systolic BP had declined by 5.1 (2.4) mm Hg (P<.001; paired 2-tailed t test) and mean (SD) diastolic BP by 1.8 (2.0) mm Hg (P = .002; paired 2-tailed t test) compared with PFC. After discontinuation of PRC consumption, BP returned to preintervention values within 2 days. Heart rate was not affected by either treatment. There were no sex differences in the effects of chocolate on BP. None of the participants reached the predefined threshold that would have required antihypertensive drug therapy. Daily energy intake and macronutrient composition remained stable throughout the study. Body mass index, 24-hour urinary excretion of sodium, potassium, and total nitrogen, as well as fasting plasma concentrations of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and glucose were not significantly different between the run-in phase and the postintervention periods.
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