is nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to muscle and nerve cells.Controversy
Creatine use in sports as a purported performance enhancer (creatine supplement) is controversial. Even if creatine's effectiveness is proven, some people still believe it should be banned from use as a performance enhancer. In any case, creatine still remains a commonly-used substance.Side Effects
Continuous intake of excessively high dosages of creatine may lead to any of several possible side-effects. It has been hypothesized that consistently high doses could lead to hypertension due to reduced blood water content, and dehydration, for the same reason. There is some discussion of kidney problems resulting from supplementation, but as excess creatine is not broken down into nitrogenous wastes but instead released in a more benign form, this is unlikely.
Creatine supplementation utilizing proper cycling and dosages, however, has not been linked with any adverse side-effects beyond occasional dehydration due to increased muscular water uptake from the rest of the body.http://en.wikipedia.org/wiki/Creatine