Although I would not advise trading in your gym membership for a lifetime supply of chocolate, it is still amazing how study after study confirms the health benefits of consuming healthy dark chocolate.
In this study, scientists from Columbia University and NYU gave a daily dose of flavanols extracted from cocoa powder to a small number of healthy 50 - 69 year old subjects. Over the course of three months, half the participants were given a small dose of flavanols, and the other a large dose. To no surprise, those who received a high dose of flavanols had much higher memory scores than those who got a low dose. These findings were even more dramatic than the increases in cognitive function obtained from an exercise program with the same group.
When looking for dark chocolate with the most health benefits, look for products that have at least 70% cacao content, no refined sugars , and are made with minimally processed raw (unroasted) cacao beans.