Foods that at one time were believed not to contribute to a healthy diet, such as garlic, onions and green tea, are currently gaining celebrity status as scientists discover these plant-based foods and many others are rich sources of phytochemicals. Take chocolate for example. Until recently, many people viewed chocolate as a sweet temptation that melted empty calories in your mouth. However, preliminary research indicates that cocoa and chocolate may have potential health benefits including maintaining cardiovascular health.
Flavonoids found within chocolate make it a potentially heart healthy food. It is estimated that there are over 4000 different flavonoids, many of which are found in a wide variety of plant-based foods and beverages such as fruits, vegetables, wine, tea, cocoa and chocolate. Through recent advances in analytical chemistry, researchers are able to identify and quantify oligomeric flavonoids in foods, including chocolate. It is rare for a food item to be abundant in oligomeric flavonoids and-interestingly enough-chocolate has been identified as having a large number of these compounds. To date, several epidemiological studies have shown flavonoids to be associated with a decreased risk of coronary heart disease and stroke1-3. These studies have laid the groundwork for further research to elucidate the potential mechanisms involved. Recent clinical studies show cocoa and chocolate may have beneficial effects on several cardiovascular health markers, including platelet activity, antioxidant capacity of the blood and vascular tone4-9.
The flavonoids, known as procyanidins, found in cocoa and chocolate are potent antioxidants10. This has been confirmed by Oxygen Radical Absorbance Capacity (ORAC) data, a test-tube analysis that measures total antioxidant power of common foods. The ORAC data identified chocolate and cocoa as having potent antioxidant potential (Figure 1) and Admanson et al. report the antioxidant capability of chocolate to have a linear relationship with the flavonoid content (R2 = 0.994) (Figure 2)11. Antioxidants are powerful compounds that can neutralize free radicals, which can cause damage to blood vessel walls. In vitro studies12,13 show that procyanidins in chocolate are found to curtail LDL oxidation. These are potentially important findings because oxidation can inflame vessels fostering a dangerous rupture of atherosclerotic plaque14.
Recently, a well-controlled pilot clinical study using a high flavonoid cocoa beverage suggested that the flavonoids in chocolate may modulate platelet activation and aggregation pathways15. Markers associated with platelet aggregation and activation were decreased and clotting of the blood was prolonged ex vivo after volunteers consumed the cocoa beverage. Using isolated cocoa flavonoids, Karim et al. observed endothelial-dependent relaxation of the vessels in vitro16. These results suggest that cocoa and chocolate flavonoids may have beneficial cardiovascular health effects that extend beyond their antioxidant capabilities.
How does this translate to our biology? In order to answer this question, we must first understand bioavailability, the degree and rate at which the flavonoids in chocolate are absorbed into the bloodstream and are made available for use. To date, studies show that two hours after the consumption of certain chocolates there is an increase in one-unit flavonoids in the blood17-19. At the same time, a downward trend has been observed in the blood's antioxidant capacity and lipid oxidative products as chocolate increases from a single serving of 27g to three servings of 80g19. Interestingly enough, the oxidative effects from the metabolism of the control (bread) were blunted by the consumption of chocolate19. These preliminary results lay the groundwork for further studies to elucidate the potential benefits of cocoa and chocolate.
References
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