In muscles, creatine is used to form phosphocreatine, which can be used to supply energy needed for muscle contractions. It has been suggested that by increasing creatine in the diet, one may increase the amount of phosphocreatine in the muscle, which would then provide a greater availability of high energy phosphate for energy production during muscle contraction. Over the past few years, studies have examined these questions, with differing results. One study by Greenhaff, et. So, as you can see, there are no definitive answers to these questions.
Creatine is available through the diet in meats.
The amount taken in through commercially marketed supplements is far greater than one would be able to ingest via food. No one really knows how much is too much. A short term side effect of creatine supplementation, that has been duplicated, is weight gain. It is believed that this gain is due to an increase in total body water. The effect on long term lean body mass increases has not been established, because none of the completed studies have looked at creatine use during a period of more than one month.