Not all performance-enhancing drugs are banned. When I get to the gym, especially if it’s early in the morning, a quick shot of caffeine, in the form of a cup of tea, is a vital part of my warm-up. If I were a bit more serious than I am, I might also make time to take a shot of creatine, too.

Unlike most supplements, whose main effect is to slim your wallet, there’s plenty of good evidence that creatine works. It won’t do much for your marathon time, but by boosting the energy system that muscles rely on for short bursts of power, it will help you sprint past a defender or squeeze out an extra rep or two in the gym. And there is some evidence—though not quite so robust—that it might have mental benefits too. Neurons are hungry for energy just like muscles are, and it seems creatine might help with depression, or defend against the effects of concussions.