Yes, yes I’m going with an unfounded and sensational headline. But its justified – there’s been a study that has shown some promising results that small amounts of dark chocolate is beneficial or specifically the flavional epicatechin (the principle component of cocoa). As reported in the New York Times
By and large, the animals that had been drinking water were the first to give out during the treadmill test. They became exhausted more quickly than the animals that had received epicatechin. Even the control mice that had lightly exercised grew tired more quickly than the nonexercising mice that had been given epicatechin. The fittest rodents, however, were those that had combined epicatechin and exercise. They covered about 50 percent more distance than the control animals.
The muscle biopsies offered some explanation for their dominance. The muscles of all of the animals that had been given epicatechin contained new capillaries, as well as biochemical markers indicating that their cells were making new mitochondria. Mitochondria are structures in cells that produce cellular energy. The more functioning mitochondria a muscle contains, the healthier and more fatigue-resistant it is.
The leg muscles of the mice that had been given epicatechin and exercised displayed far more mitochondrial activity than the leg muscles of the control mice. Even the mice that had drunk epicatechin and not exercised contained markers of increased mitochondrial health, suggesting that the flavonol prompts a physiological reaction even among the sedentary. But that response is greatly heightened by exercise, no matter how slight.
So eating small amounts of dark chocolate helps you if you don’t exercise, and even more if you do? I’m not sure I want to see any further studies that might negate this. However, epicatechin is closely related to the green tea extract (epigallocatechin-3-gallate; EGCG) which some studies have investigated for endurance enhancement and found lacking (here and here). What I’d like to take from that is that clearly its only chocolate, and not green tea that will help.