The sleep issue suggests an answer to the conundrum of how caffeine could be a source of human energy. It only looks that way, because caffeine is simply hiding, or postponing, our exhaustion by blocking the action of adenosine. As the liver removes the caffeine from circulation, the dam holding back all that pent-up, still-mounting adenosine will break, and when the rebounding chemical floods the brain you will crash, feeling even more tired than you did before that first cup of coffee.
