Creatine is a legal performance-enhancing supplement and a staple of sports nutrition. It is one of the few supplements with a solid evidence base behind it. A review paper from 2017 concluded that it can give athletes a 10-20% performance boost in brief bouts of high-intensity exercise, such as sprinting or lifting heavy weights. It appears to be safe, with no worrying side-effects seen even in people who have been taking it for years. Because no test can distinguish supplementary creatine from the sort naturally produced by the body, or the kind found in meat and fish, most sports do not consider taking it to be doping.
Cells use adenosine triphosphate (ATP) as a carrier of chemical energy. Aerobic respiration, which uses oxygen to break down fats or sugar, is the most efficient way of making ATP but is relatively slow. When muscles need a lot of ATP in a hurry, most of it is supplied by the phosphocreatine system. When muscles contract, the ATP molecules used to power that contraction lose one of their three phosphate groups, turning into adenosine diphosphate (ADP). Phosphocreatine stored in the muscles donates a replacement phosphate group, turning ADP back into ATP. Reserves are sufficient for only a few seconds of maximal effort. Creatine supplements boost the amount of phosphocreatine that can be stored, allowing users to squeeze out extra repetitions or sprint at full power for a second longer.
A growing body of research suggests creatine may benefit brains as well as muscles. Neurons need ATP just as muscle cells do. Some studies, summarised in a review published in 2021 in Nutrients, have suggested that creatine might sharpen short-term memory or reaction times. Others have reported it may lessen the symptoms of depression, and tentative evidence suggests it improves cognition in those with Alzheimer's disease. Both conditions may be associated with a misallocation of energy within the brain. In animals, creatine appears to protect against the effects of concussions: in one study, rats given creatine supplements showed a 50% reduction in damage after being given an artificially induced brain injury.
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