BRUSSELS, BELGIUM. Oral supplementation with creatine monohydrate is widely used among athletes in order to improve their performance and maximize the effect of intense training sessions. Individual doses of 1 to 20 grams of creatine may be taken up to four times a day. Creatine contains 32 per cent nitrogen and some concern has been expressed that its excretion may put an added burden on the kidneys. Researchers at the University of Brussels have recently released the results of a study which concludes that long-term supplementation with creatine is quite safe, at least among healthy athletes. The study involved eight young men and one woman aged between 21 and 27 years. The participants had been taking creatine daily for periods ranging from 10 months to 5 years. Blood plasma levels and urine excretion rates for creatine, urea, and albumin were compared between the creatine users and a control group of 85 male students who did not use creatine. No differences were found. The researchers conclude that glomerular filtration rate, tubular reabsorption, and glomerular membrane permeability were normal in both groups and that daily creatine supplementation for up to five years is safe in healthy athletes. They caution though that people with suspected renal dysfunction should not take creatine.
Poortmans, Jacques R. and Francaux, Marc. Long-term oral creatine supplementation does not impair renal function in healthy athletes. Medicine and Science in Sports and Exercise, Vol. 31, August 1999, pp. 1108-10