|Cocoa pods and seeds. Source: Lolay (CC: 2.0)|
Of course, it is the quality of the cocoa that makes all the difference. In a study of sixty older adults, with an average age of 73 and all with either hypertension or type II diabetes, volunteers had two cups every day of a cocoa beverage that was either rich or depleted in flavonols. Everyone had their cognitive function and neurovascular coupling measured before the study, on day 1 and on day 30, the last day. Neurovascular coupling is the ability of blood vessels to increase the delivery of oxygen and nutrients to areas of the brain that suddenly become more active while you're doing something. After 24 hours, volunteers with previously poor neurovascular coupling had this parameter improve by 10.6%, and at 30 days their scores on a test measuring attention significantly improved. Before the study, they took an average of 167 seconds (2 minutes and 47 seconds) to complete the test, but after 30 days this was shortened to 116 seconds (just under 2 minutes). Surprisingly, both flavonol-rich and poor drinks had the same effects. Another study on younger adults, with an average age of 33, found that it may be the small amount of caffeine in cocoa together with another phytochemical, theobromine, that is responsible for its cognition-boosting effects. It is most likely to be the result of all phytochemicals in cocoa working together.
As for spearmint, some of its phenolic compounds inhibit the acetylcholinesterase enzyme, thus increasing levels of the neurotransmitter acetylcholine. This is critical for cognitive function and memory. One phenolic, rosmarinic acid, has been shown to protect neurons in the brain's memory centres against oxidative stress, which can kill cells if severe enough. To make things even better, rosmarinic acid and some other phenols in spearmint can even increase the growth factors required to make new brain cells! The old paradigm of "no new neurons" is gone. Overall, perhaps hot chocolate isn't so bad after all, but watch for quality and sugar content.