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Death by Chocolate…NOT!
Abstract & Commentary
By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital,Lexington. Dr. Phillips reports no financial relationship to this field of study.
Synopsis: In a small sample of adults who were healthy except for elevated blood pressure, addition of small amounts of dark chocolate to their usual diet resulted in lowered blood pressure and improved formation of vasodilative nitric oxide.
Source: Taubert D, et al. Effects of Low Habitual Cocoa Intake on Blood Pressure and Bioactive Nitric Oxide. A Randomized Controlled Trial JAMA. 2007;298:49-60.
German investigators recruited 44 older adults who had untreated stage 1 hypertension but were otherwise healthy. Participants were randomly assigned to receive either 6.3 grams (30 kcal) per day of dark chocolate containing 30 mg of polyphenols or matching polyphenol-free white chocolate for 18 weeks. At the end of 18 weeks, those subjects who were assigned to the dark chocolate group experienced a fall in systolic blood pressure of 2.9 (1.6) mm Hg (P < .001); their diastolic blood pressure fell –1.9 (1.0) mm Hg (P < .001). There were no changes in body weight, plasma levels of lipids, glucose, or 8-isoprostane. In the dark chocolate group, overall hypertension prevalence fell from 86% to 68%. In addition, plasma markers of vasodilating substances increased. White chocolate intake caused no changes in blood pressure or plasma biomarkers. The authors concluded that including amounts of polyphenol-rich dark chocolate as part of a usual diet can lower blood pressure and increase formation of vasodilative nitric oxide.
Chocolate lovers are feeling vindicated by the findings of this study. Indeed, this report has received attention in the lay press. There are a couple of points to emphasize here, however:
1. Only dark chocolate was associated with lowered blood pressure in this study;
2. Small amounts of chocolate were used. In otherwords, this paper cannot be used as justification to eat an entire white chocolate Easter bunny, and we are left not knowing anything about the effects of milk chocolate on blood pressure.
What is the rationale for using chocolate to lower blood pressure? Polyphenols in fruits and vegetables are believed to be major contributors to the health benefits of dietary plant intake, including lowered cardiovascular risk.1-3 It turns out that cocoa contains significant amounts of phenol as well.4-6 Indeed, cocoa intake has been shown to lower blood pressure and improve endothelial function in human intervention studies, but these studies have heretofore been short term (no more than 2 weeks) and involved huge doses of cocoa.7-9 What the current study adds to the literature is longer-term (more than 4 months) follow-up and evidence that there were no adverse effects on body weight, lipids, or blood glucose associated with dietary intake of chocolate. Further, it helps to establish that the fall in blood pressure was associated with increases in circulating levels of vasodilative S-nitrosoglutathione, suggesting a causative role of S-nitrosoglutathione for blood pressure regulation.
In this randomized, controlled trial, these investigators have demonstrated that small amounts of commercial cocoa have comparable benefit in lowering blood pressure as do comprehensive dietary modifications that have proven efficacy to reduce cardiovascular event rate.10, 11 Those of us who spend our days trying to get humans to change their behavior may find it easy to recommend that our patients eat (a small amount of dark) chocolate, along with our usual, predictable admonitions about exercise, smoking cessation, alcohol restriction, and adequate sleep.
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2. Joshipura KJ, et al. Ann Intern Med. 2001;134(12):1106-1114.
3. He FJ, et al. Lancet. 2006;367(9507):320-326.
4. Arts IC, et al. Chocolate as a source of tea flavonoids. Lancet. 1999;354(9177):488.
5. Vinson JA, et al. J Agric Food Chem. 2006;54(21):8071-8076.
6. Hollenberg NK, et al. Br J Cardiol. 2004;11(5):379-386.
7. Taubert D, et al. JAMA. 2003;290(8):1029-1030.
8. Grassi D, et al. Am J Clin Nutr. 2005;81(3):611-614.
9. Grassi D, et al. Hypertension. 2005;46(2):398-405.
10. Appel LJ, et al. JAMA. 2003;289(16):2083-2093.
11. McCullough ML, et al. Am J Clin Nutr. 2000;72(5):1214-1222.