Creatine

Creatine increases your muscles' stored phosphocreatine, allowing you to regenerate ATP more efficiently during short intense efforts. That means better training performance and over time greater gains in strength and lean muscle. It's one of the most thoroughly researched sports supplements available with an excellent safety profile. Creatine isn't just for muscle, either -- the brain relies on the same phosphocreatine-to-ATP system for rapid energy, and supplementation has been linked to improved short-term memory, reasoning, and mental performance, particularly during sleep deprivation, high mental stress, older age, or in people with lower dietary creatine intake such as vegetarians. Evidence in healthy young adults is more mixed, but the overall cognitive picture is promising and comes with the same strong safety profile as creatine's muscle-building use at standard doses.