Is Hershey's Heart Healthy?
Abstract & Commentary
By Allan J. Wilke, MD, Professor, Department of Introduction to Clinical Medicine, Ross University School of Medicine, Commonwealth of Dominica. Dr. Wilke reports no financial relationships relevant to this field of study.
Synopsis: Eating chocolate may be part of a healthy lifestyle.
Source: Buitrago-Lopez A, et al. Chocolate consumption and cardiometabolic disorders: Systematic review and meta-analysis. BMJ 2011 Aug 26;343:d4488. doi: 10.1136/bmj.d4488.
This is a systematic review and meta-analysis that buitrago- Lopez and colleagues designed to test the association between dietary chocolate and the risk of developing certain cardiovascular disorders (coronary heart disease, stroke, congestive heart failure, and myocardial infarction), diabetes, and the metabolic syndrome. They searched the literature, including Medline, Embase, the Cochrane Library, Scopus, Scielo, Web of Knowledge, AMED, and CINAHL, in the summer of 2010, looking for randomized control trials or cohort, case-control, or cross-sectional studies. Reports were included if they studied non-pregnant adults only and included the disorders of interest. They went back to the authors of the papers that met their criteria for any additional information. Beginning with 4576 references, they eliminated all but seven. These studies include one cross-sectional study from United States and 6 cohort studies from Europe, Asia, and North America. The seven studies included 114,000 mostly white subjects, ranging in age from 25 to 93 years. The studies did not distinguish between dark and white chocolate consumption, but one did report cocoa consumption. Chocolate was consumed in a variety of forms, including candy bars, drinks, snacks, and nutritional supplements. There was no uniformity among the seven studies in how chocolate consumption was measured. Follow-up in the cohort studies ranged from 8 to 16 years. The studies were scored for quality. None of the studies were at the highest level of quality (6 points), but all of them scored in the adequate range (4 or 5 points). For the purpose of this meta-analysis, the authors chose to look at only the lowest and the highest levels of chocolate intake for each study. Five of the studies showed an inverse relationship between chocolate intake at the highest level and the development of the diseases of interest. Chocolate intake was associated with a reduction in risk of 29% (for stroke) to 37% (for cardiovascular disease), all statistically significant. The only disorder that did not show a significant beneficial association was heart failure, but it trended that way.
Commentary
I love studies that validate what I'm already doing.
This is not the last word on the subject. None of the studies included in this meta-analysis were randomized controlled studies, so the best that can be concluded is that there is an association (but not causation) between chocolate intake and reduction in risk of some cardiovascular diseases, diabetes, and the metabolic syndrome. This meta-analysis does raise several questions. Why isn't heart failure in the list? Since heart failure is a late sequela of heart disease, it may be that it was too late for chocolate to have any effect. How much chocolate needs to be consumed? Is there a dose response? Are there differences between types of chocolate? I'm pulling for dark.
Assuming for the moment that chocolate consumption does reduce risk, how does it do it? A component of chocolate is flavonol also present in kale, broccoli, tomato, apple, grape, tea, and red wine which is associated with a reduction in risk of coronary heart disease mortality.1 Chocolate has antioxidant,2 antihypertensive,3 and anti-inflammatory effects.4 It increases insulin sensitivity, improves vascular endothelial function, and combats atherogenesis and thrombosis.5
Chocolate dates back to the Mayan and Aztec peoples who used it in religious ceremonies. They did not add sugar to it. At the turn of this century, a major U.S. chocolate manufacturing company (not Hershey) tried to capitalize on the burgeoning research into the positive health effects of cocoa flavonols and introduced a line of snacks with "real chocolate pleasure, real heart health benefits."6,7 Chocolate, as it is usually consumed today, cannot be considered a health food. Typically, it is accompanied by large amounts of fat and sugar to make it more palatable. Encouraging chocolate consumption could have the unintended consequence of increasing cardiovascular risk.
The authors conclude, "Corroboration is now required from further studies, especially experimental studies to test causation rather than just association." I want to be part of the intervention group! With the ubiquity of chocolate in our environment, however, I suspect it would be very difficult to do a double-blind, randomized, controlled study. Can you imagine a "chocolate-like" placebo? I think the best advice we can give our patients is that chocolate is not associated with any harmful cardiovascular or metabolic effects, and as with so many other pleasurable things in life, is best enjoyed in moderation.
References
1. Huxley RR, Neil HA. The relation between dietary flavonol intake and coronary heart disease mortality: A meta-analysis of prospective cohort studies. Eur J Clin Nutr 2003;57:904-908.
2. Katz DL, et al. Cocoa and chocolate in human health and disease. Antioxid Redox Signal 2011;15:2779-2811.
3. Desch S, et al. Effect of cocoa products on blood pressure: Systematic review and meta-analysis. Am J Hypertens 2010;23:97-103.
4. Selmi C, et al. Chocolate at heart: The anti-inflammatory impact of cocoa flavanols. Mol Nutr Food Res 2008;52:1340-1348.
5. Lippi G, et al. Dark chocolate: Consumption for pleasure or therapy? J Thromb Thrombolysis 2009;28:482-488.
6. http://www.health.harvard.edu/press_releases/cocoavia_health_facts. Accessed October 24, 2011.
7. http://en.wikipedia.org/wiki/CocoaVia. Accessed October 24, 2011.
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