Published online before print October 17, 2005, doi: 10.1161/01.HYP.0000188406.38247.fd
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(Hypertension. 2005;46:e17.)
© 2005 American Heart Association, Inc.
Hypertension Electronic Pages |
Hypertension, Diabetes
Department of Pharmacology, Ernst Moritz Arndt University Greifswald, Greifswald, Germany
I have read with interest and acknowledge the recent article by Grassi et al1 published in your journal. The authors supported evidence that dark chocolate decreased blood pressure and serum LDL cholesterol and ameliorated insulin sensitivity in hypertensives. The authors claim that flavanols from cocoa products may provide these benefits if included as part of a healthy diet for patients with essential hypertension.
Without doubt, cacao beans, a main ingredient of chocolate (more so in dark chocolate), contain >600 plant chemicals, including antioxidant phytochemicals such as flavonoids, which may protect against heart disease and other maladies. Unfortunately, I was unable to recognize any evidence in this study of a causal relationship between these flavonoids and the patients’ outcome. Thus, the question arises whether the effects shown are induced by ingredients of dark chocolate other than flavonoids or, at best, whether the effects seen are the result of a multifactorial interaction of substances present in cocoa.
Dark chocolate is known to be rich in magnesium, concentrations being in the range of 300 mg/100 g. Thus, a bar of this chocolate supplies the recommended daily allowance of magnesium. Magnesium is considered a physiological calcium antagonist. There are many reports describing effects of magnesium in hypertension and other cardiovascular diseases as well as in insulin action and metabolic syndrome.2,3 Recently, a round table discussion has been reported in which issues of renal magnesium clearance, magnesium and arrhythmic risk, ion balance in heart failure, diabetes, ischemic stress, oxidative stress in the cardiomyopathy of magnesium deficiency, and the role of electrolyte balance in hypertension were discussed.4
Thus, flavonoids as well as magnesium are known for their beneficial effects. Both are present in considerably higher concentrations in dark than in white chocolate. It would be worth examining whether the beneficial effects shown by Grassi et al1 are the result of these two or even more substances in combination. Antioxidative flavonoids together with pharmacological actions of magnesium could be a candidate for such an effective combination.5
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- Grassi D, Necozione S, Lippi C, Croce G, Valeri L, Pasqualetti P, Desideri G, Blumberg JB, Ferri C. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension. . 2005; 46: 398–405.
[Abstract/Free Full Text] - Touyz RM. Role of magnesium in the pathogenesis of hypertension. Mol Aspects Med. . 2003; 24: 107–136.[CrossRef][Medline] [Order article via Infotrieve]
- Song Y, Ridker PM, Manson JE, Cook NR, Buring JE, Liu S. Magnesium intake, C-reactive protein, and the prevalence of metabolic syndrome in middle-aged and older US women. Diabetes Care. . 2005; 28: 1438–1444.
[Abstract/Free Full Text] - Weglicki W, Quamme G, Tucker K, Haigney M, Resnick L. Potassium, magnesium, and electrolyte imbalance and complications in disease management. Clin Exp Hypertens. . 2005; 27: 95–112.[CrossRef][Medline] [Order article via Infotrieve]
- Bukoski RD. Reactive oxygen species: the missing link between magnesium deficiency and hypertension? J Hypertens. 2002; 20: 2141–2143.[Medline] [Order article via Infotrieve]
Response
Department of Internal Medicine and Public Health, University of L’Aquila, L’Aquila, Italy
Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts
Department of Internal Medicine and Public Health, University of L’Aquila, L’Aquila, Italy
The suggestion by Professor Meisel of a potential contribution by magnesium to the beneficial effects of dark chocolate we observed in blood pressure and insulin resistance is intriguing. Although we did not measure plasma flavanol or proanthocyanidin status in our subjects, the dark chocolate we tested contained 500 mg total polyphenols/100 g.1 Experimental studies reveal a direct action of these compounds on NO-mediated vascular responses, and clinical trials demonstrate their bioavailability and cardiovascular actions.2 Thus, it is reasonable to presume a causal relationship between the chocolate flavanols and our clinical findings. Nonetheless, &100 mg/100 g magnesium is present in dark chocolate, with much lower amounts found in milk and white chocolate.3 We did not determine daily magnesium intake in our subjects but estimate it at 280 to 300 mg, similar to that reported in a comparable population.4 Animal models of magnesium deficiency have indicated an association between hypertension and an increased production of reactive oxygen species and an elevation of MAP kinase–dependent signaling.5 Although evidence from human studies remains equivocal, supplementation with magnesium has been shown to significantly lower blood pressure in patients with essential hypertension.5 Thus, the increase in magnesium intake associated with consumption of dark chocolate may have contributed to the beneficial outcomes found in our study. We agree with Meisel and suggest that further investigation into the potential additive or synergistic interaction between flavonoids and magnesium is warranted.
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TopReferencesReferences |
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- Grassi D, Necozione S, Lippi C, Croce G, Valeri L, Pasqualetti P, Desideri G, Blumberg JB, Ferri C. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension. . 2005; 46: 398–405.
[Abstract/Free Full Text] - Engler MB, Engler MM. The vasculoprotective effects of flavonoid-rich cocoa and chocolate. Nutr Res. . 2003; 24: 695–706.[CrossRef]
- Bruinsma K, Taren DL. Chocolate: food or drug? J Am Diet Assoc. . 1999; 99: 1249–1256.[Medline] [Order article via Infotrieve]
- Turrini A, Lintas C, Saba A. Study of the Italian reference diet for monitoring food constituents and contaminants. Nutr Res. . 1991; 11: 861–874.
- Touyz RM. Role of magnesium in the pathogenesis of hypertension. Mol Aspects Med. . 2003; 24: 107–136.[CrossRef][Medline] [Order article via Infotrieve]
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