Green tea and red wine are powerhouses of flavonoid content, the plant-sourced family of compounds that are believed to be the source of health benefits of vegetables and fruits.
What has more flavonoids than both green tea (brewed) and red wine?
Cocoa. Cocoa has more flavonoids, gram for gram. This means that flavonoids, such as catechin and epicatechin, as well as their polymers, the anthocyanidins, are present in larger quantities in cocoa than in most other flavonoid-rich foods. In one recent analysis, the quantity of flavonoids and polyphenols provided by 2 tbsp of cocoa powder (undutched, i.e., not treated with alkali) exceeded the flavonoids and polyphenols in brewed green and black tea by 3 to 15-fold. Only red wine provided something close to cocoa, and even then cocoa exceeded the red wine flavonoid and polyphenol content by nearly two-fold.
Cocoa is the most concentrated means to obtain cocoa flavonoids. However, widely available dark chocolates are making it increasingly easy and convenient. A 40-gram (approximately 2 inches square) serving of 70% cocoa chocolate provides approximately the same quantity of flavonoids and polyphenols as a 4-oz glass of red wine. (A much larger serving of milk chocolate would be required to yield the same quantity of flavonoids.)
Cocoa flavonoids are the components responsible for cocoa's blood pressure-reducing and HDL-increasing effects. Relatively flavonoid-poor milk chocolate, for instance, does not increase HDL, while flavonoid-rich dark chocolates increase HDL. HDL can be increased by as much as 24% by daily cocoa consumption, increasing, say, HDL from 40 mg/dl to around 50 mg/dl. Cocoa flavonoids exert anti-inflammatory effects, including reduced levels of inflammation-provoking leukotrienes and decreasing anti-inflammatory prostacyclin. Other anti-inflammatory effects have been documented, including reduced activation of the lipoxygenase pathways. Platelet-inhibiting effects have also been identified, similar to the effect of aspirin. Consumption of 259 mg catechins and anthocyanidins from dark chocolate per day has been shown to improve endothelial function, i.e., cause a relaxation effect in arteries, after 2 weeks.
Cocoa adds to daily intake of flavonoids that reduce cardiovascular risk. Of the 11 prospective studies examining flavonoid/catechin intake and cardiovascular risk, 9 studies have demonstrated reduced heart attack and cardiac mortality with higher intakes.
The difficulty with cocoa is its bitterness and, for this reason, sweeteners are necessary to make the bitter cocoa palatable. (Unsweetened cocoa is enjoyed by a few, but most find it intolerably bitter.) The need for sweeteners introduces the one potentially unhealthy aspect of cocoa, since the vast majority of cocoa products are wildly oversweetened to suit the excessively sweet-desiring American public. However, for heart health, we want all the benefits of cocoa with as little sweetener as possible. Thus, cocoa powder used in hot chocolate using as little sweetener as possible, or dark chocolates with at least 70%, if not 85-90%, cocoa, are the best ways to get cocoa flavonoids with as little sugar as possible.
Dark chocolate is also rich in cocoa butter. Cocoa butter adds to texture, taste, and "mouthfeel," an important aspect of enjoying cocoa as chocolate. The smoothest, richest dark chocolates tend to be around 50% (by weight) cocoa butter. Although cocoa butter is rich in saturated fat, much of it is stearic acid, a saturated fatty acid that is relatively neutral and exerts little to no LDL cholesterol-increasing effect.
So, from a heart health standpoint, we want as much cocoa and cocoa butter as possible, as little sweetener as possible.