CYCLING PERFORMANCE TIPS - creatine toxicity


Creatine Toxicity

The following was excerpted from the Sportscience web site


Will G Hopkins PhD, Physiology and Physical Education, University of Otago, Dunedin 9001, New Zealand. Email: Sportscience 4(1),, 2000 (476 words)

Creatine supplementation for a week or so probably enhances performance of repeated sprints by a few percent in some sports, and continued supplementation combined with training appears to have a more substantial anabolic effect on strength. Creatine supplements work by increasing the amount of creatine in muscle, where it helps you perform short, high-intensity activities. You have to take a lot of creatine to get any extra into muscle, and most of what you take ends up in your urine. That's why there's some concern that creatine supplementation could damage kidneys. To get rid of the extra creatine, you have to make more urine--about 25% more each day, according to a recent study of long-term users by Poortmans and Francaux (1999). Does that produce some sort of strain on the kidneys that might eventually lead to kidney disease?

Poortmans and Francaux couldn't find any indication of failing kidneys in nine athletes who had been taking creatine for up to five years, but is nine subjects enough to declare creatine kidney-friendly? Kuehl and coworkers didn't think so, in a letter to the editor in the January issue of Medicine and Science in Sports and Exercise. They had other criticisms that didn't stand up to close scrutiny, but in his reply Jacque Poortmans acknowledged that "larger studies should be implemented". Richard Kreider and his coworkers are doing their best to remedy that problem: there is no evidence of serious side effects in their many recent studies, or in the abstracts of several studies to be presented at this year's annual meeting of the American College of Sports Medicine.

But... the letters to the editor of Med Sci Sports referred to two case studies of inflamed kidneys apparently resulting from creatine supplementation. In one case an existing kidney condition flared up when the athlete started taking creatine; in the other case the athlete developed serious inflammation of the kidneys. Are these cases the tip of an iceberg? Probably not: it's likely that only one athlete in many thousand will suffer from kidney problems when taking creatine supplements. The risk is very low, but it is certainly not zero. And the risk is almost certainly much higher for someone who already has a kidney condition.

Poortmans JR, Francaux M (1999). Long-term oral creatine supplementation does not impair renal function in healthy athletes. Medicine and Science in Sports and Exercise 31, 1108-1110

Kuehl K, Goldberg L, Elliot D. (2000). Re: long-term oral creatine supplementation does not impair renal function in healthy athletes. Medicine and Science in Sports and Exercise 32, 248

Poortmans JR (2000). Response. Medicine and Science in Sports and Exercise 32, 248-249

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