"Nutritional Supplements: Creatine Monohydrate"

Creatine monohydrate has been used as an ergogenic aid since the early 1970's. In the United States, it's use surged in the 1990's. This also correlated with scientific evidence demonstrating that supplemental creatine monohydrate has ergogenic (performance enhancing) properties in athletes. By virtue of its sales and known efficacy, it is the most popular dietary supplement among strength athletes today.

What is Creatine and how does it work?
Creatine is found in the diet. The body will synthesize about one-half of a person's daily creatine needs from amino acids. Meat or fish are the best natural sources. For example, there is about 1 g of creatine in 250 g (half a pound) of raw meat. However, the primary way that athletes "load" the muscle with creatine is through supplementation with synthetic creatine monohydrate.
Creatine is mostly stored in muscles where it is used as a buffer. When we exercise there is an associated increase in the need for energy. During increased energy demands, phosphocreatine provides phosphate to adenosine diphosphate (ADP) to produce adenosine triphosphate (ATP), the body's energy currency. Exercise that demands short bursts of energy relies upon both ATP and phosphocreatine for energy. Supplementing with creatine will increase creatine phosphate stores (as well as circulating creatine levels). Thus the person who uses creatine monohydrate and exercises at a high intensity will have the "extra" creatine readily available so that the body can exercise harder and recover quicker.
Although most studies indicate that creatine monohydrate supplementation may improve performance, it may not provide ergogenic value for everyone. It is possible that subject variability in response to the supplementation may account for the lack of ergogenic benefit reported in some studies.

Side Effects
The only side effect from clinical studies in preoperative and post-operative patients, untrained subjects, and elite athletes has been weight gain. Any claims in lay publications or on the internet, that creatine is "unsafe" have not been substantiated in any prospective creatine monohydrate study.
Since creatine is an amino acid, it has been suggested that creatine monohydrate supplementation may affect kidney and/or liver function. However, no studies have reported clinically significant elevations in kidney function markers or liver enzymes in response to creatine monohydrate supplementation. There has also has been recent concern on the potential harmful effect of nutritional supplementation on athletes who participate in summer sports, but no study has also found that creatine supplementation has any negative effects on athletes (medical markers of safety) who participate in outdoor summer-type sports.

Conclusion
To date, there are over 500 studies on this ergogenic aid. Creatine monohydrate supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Not all of the studies examining athletic uses demonstrate an ergogenic effect; approximately 30% do not support the effect, although some report non-significant positive effects or influence of creatine monohydrate. Future research will determine what dose may be best for athletic uses.