Dark chocolate is healthy because it is not milk chocolate. The higher cocoa content of dark chocolate provides more flavonoids -- a subset of phenols -- that are similar to those found in red wine. Scientific evidence as reviewed by Eric Ding in the January 2006 issue of "Nutrition & Metabolism," supports dark chocolate as having some of the same cardiovascular health benefits attributed to red wine. Ding points out the limitations of the available evidence and concludes that long-term chocolate feeding trials are needed before the evidence can be considered definitive.
Types of Chocolate
"The Emperors of Chocolate," by Joel Glenn Brenner, an entertaining book about the fierce competition between Hershey and Mars, includes a history of the transition of cocoa from Aztec beverage to American candy. In the U.S., milk chocolate is only 10 percent to 20 percent cacao solids, which include both cocoa powder and cocoa butter. Dark chocolate candy bars range from 30 percent to 80 percent cacao solids, with the amount often stated on the label as "% cocoa," but not required. Whatever is not cacao solids is milk and sugar. Flavonoids are a family of chemical compounds in the cocoa powder that are responsible for the bitter taste and astringent sensation of high-cacao dark chocolates.
Health Evidence
Evidence of health benefits of dark chocolate is circumstantial. According to Dr. Roberto Corti's review in the March 2009 issue of "Circulation," in clinical trials comparing high-flavonoid to low-flavonoid chocolate, individuals that consumed the high version had lower blood pressure, less insulin sensitivity, less sticky platelets and evidence of more flexible arteries. While these changes are in theory beneficial, none of the trials were long enough or large enough to learn if the results would actually show a lowered incidence of cardiovascular disease.
Misconception - Not Antioxidants
Although marketing efforts often position dark chocolate and other foods that contain flavonoids as containing potent antioxidants, leading researchers in this field are beginning to believe that these molecules, while having antioxidant activity, are functioning via mechanisms that have little to do with combating oxidation. Dr. Helmut Sies, in an editorial in the June 2007 issue of "The Journal of Nutrition," discourages the theory that test-tube measurements of antioxidant activity are relevant to what is actually happening after these molecules are absorbed. Dr. Corti's review describes the ability of flavonoids to enter cell nuclei and activate genes responsible for making specific proteins. One of these -- endothelial nitric oxide synthase -- appears to be responsible for the improvements in artery and platelet status.
Practical Applications
Human research in the form of controlled clinical trials and epidemiological studies supports including two to three servings per day of flavonoid-containing foods as part of a healthy diet. There is no evidence that more is better. Dark chocolate can play a part, but shifting towards a diet with more fruits and vegetables or a Mediterranean-style diet would also suffice. For people who already consume moderate amounts of alcohol on a regular basis, red wine qualifies. For teetotalers, substitute green tea. The evidence for flavonoid dietary supplements is not as strong as for these functional foods.
Future
One or more of the chocolate companies may apply to the Food and Drug Administration for an approved health claim. There is a risk -- success would add official approval, but rejection would be a setback. Any application will not be for dark chocolate candy bars, as the saturated fat content disqualifies any possibility of a official health claim; but a low-fat beverage could qualify.
References
- "Nutrition & Metabolism"; Chocolate and Prevention of Cardiovascular Disease: a Systematic Review; E. Ding et al.; Jan. 3, 2006.
- "Circulation"; Cocoa and cardiovascular health; R Corti et al.; March 17, 2009.
- "American Journal of Clinical Nutrition"; Acute Dark Chocolate and Cocoa Ingestion and Endothelial Function: a Randomized Controlled Crossover Trial; Z. Faridi et al.; 2008.
- "The Journal of Nutrition"; Total Antioxidant Capacity: Appraisal of a Concept; Helmut Sies; 2007.
- "Pflugers Archive"; Nutritional Improvement of the Endothelial Control of Vascular Tone by Polyphenols: Role of NO and EDHF; V.B. Schini-Kerth et al.; Mar. 12, 2010.
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