Phosphocreatine is a compound stored in muscle; it donates phosphate to ADP and thereby rapidly replenishes ATP during anaerobic muscle contraction. It is synthesized endogenously in the liver from arginine, glycine, and methionine. Dietary sources are milk, steak, and some fish.
Creatine is said to improve physical and athletic performance and to reduce muscle fatigue. Some evidence suggests creatine is effective at increasing work done in a short maximal effort (eg, sprinting, weightlifting). It has proven therapeutic use in muscle phosphorylase deficiency (glycogen storage disease type V [McArdle disease]) and gyrate atrophy of the choroid and retina; early data also suggest possible effects in Parkinson's disease and amyotrophic lateral sclerosis.
Creatine may cause weight gain (possibly because of an increase in muscle mass) and spurious increases in serum creatinine levels. Minor GI symptoms, dehydration, electrolyte imbalance, and muscle cramps have been reported anecdotally.
Last full review/revision May 2009 by Ara DerMarderosian, PhD
Content last modified August 2013