Reviewed: Kaynak HE, Taegtmeyer H. Is bitter better? The benefits of chocolate for the cardiovascular system. Curr Hypertens Rep. 2011 Dec;13(6):401-403.
Cocoa (Theobroma cacao, Sterculiaceae) has shown blood pressure-lowering effects, but its effects on the risk of coronary heart disease (CHD) have not been investigated thoroughly. This article is a report on the cross-sectional National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study,1 with comments by the authors at the Department of Internal Medicine, Division of Cardiology, University of Texas Medical School at Houston.
In the study, intake of chocolate by 4,970 participants who were 25 to 93 years of age was assessed by using a semi-quantitative food frequency questionnaire. For subjects consuming chocolate 1-3 times per month, 1-4 times per week, or 5+ times per week, the odds ratios (OR) for CHD were 1.01 (95% confidence interval [CI], 0.76-1.37), 0.74 (95% CI, 0.56-0.98), and 0.43 (95% CI, 0.28-0.67), respectively (P for trend < 0.0001), adjusting for age, sex, family, CHD risk group, and a large number of other confounders. This shows a trend of reduced CHD incidence proportional to the increased consumption of chocolate. An additional finding was that subjects who consumed non-chocolate candy 5+ times per week had a 49% higher prevalence of CHD than those who did not (OR, 1.49; 95% CI, 0.96-2.32). The authors of the study concluded that consumption of chocolate is inversely related to CHD in the US.
Based on the above report, the authors Kaynak et al. offer the following comments:
“Cocoa contains a large number of flavanols, which have been shown to positively impact cardiovascular risk factors such as atherosclerosis, platelet function, and endothelial function and regeneration. A notable epidemiological study showed that Kuna Indians who live on an offshore island close to Panama City, Panama and drink water boiled with cocoa beans as their main beverage have a much lower incidence of hypertension even into old age.”2
By contrast, Kuna people who have moved to the mainland and who drink other beverages (including those that contain store-bought cocoa, largely devoid of flavanols) lose this benefit. In addition, a meta-analysis concluded that cocoa consumption can lower systolic blood pressure by 4.5 mm Hg and diastolic blood pressure by 2.5 mm Hg.3 Another meta-analysis with similar findings in hypertensive patients indicated a reduction of this magnitude can reduce the risk of a cardiovascular event by more than 20% over 5 years and is comparable to the effect of lifestyle modifications.4 The effect may be due to increasing the levels of nitric oxide (NO) in the blood and/or inhibition of angiotensin-converting enzyme (ACE).
Chocolate consumption has also been associated with reduction of cardiovascular disease (37%), diabetes (up to 31%), and stroke (29%). A German prospective study showed that in a healthy population, those consuming the least amount of chocolate had the highest incidence of myocardial infarction and stroke, with the inverse being true for those with the highest consumption of chocolate. Similar results were found in elderly Dutch men and postmenopausal American women.
Though many of the findings in this review are positive, the authors note that factors such as local dietary habits and genetic and ethnic disparity should be taken into account when interpreting the studies. They note that it is difficult to have a proper control for double-blind studies, since the bitterness of the flavanols gives away the treatment. Lastly, they purport that the doses of chocolate used in the studies, such as 75 g or 100 g dark chocolate daily to inhibit ACE or lower blood pressure, respectively, are too high for normal daily consumption. Therefore, they conclude that interpretation of studies and meta-analyses should be done prudently. In addition, it must be kept in mind that excessive chocolate consumption may have adverse effects on weight and blood lipid levels, due to the associated calorie intake.
Editor’s note: The potential adverse effect of excessive chocolate in food form containing relatively high levels of fat and sugar can be obviated by production of high-flavanol cocoa-derived extracts in dietary supplement form.
—Risa Schulman, PhD
- Djoussé L, Hopkins PN, North KE, Pankow JS, Arnett DK, Ellison RC. Chocolate consumption is inversely associated with prevalent coronary heart disease: The National Heart, Lung, and Blood Institute Family Heart Study. Clin Nutr. 2011;30(2):182-187.
- McCullough ML, Chevaux K, Jackson L, Preston M, Martinez G, Schmitz HH, Coletti C, Campos H, Hollenberg NK. Hypertension, the Kuna, and the epidemiology of flavanols. J Cardiovasc Pharmacol 2006, 47 Suppl 2:S103-S109.
- Desch S, Schmidt J, Kobler D, et al. Effect of cocoa products on blood pressure: systematic review and meta-analysis. Am J Hypertens. 2010;23(1):97-103.
- Ried K, Sullivan T, Fakler P, et al. Does chocolate reduce blood pressure? A meta-analysis. BMC Med. 2010;8:39.