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News & Comment / In Brief

Editorial
Vitamin C Warning
Creatine and Kidney Damage?
Liability for Side Effects

 

EDITORIAL
Will G Hopkins PhD, Physiology and Physical Education, University of Otago, Dunedin 9001, New Zealand. Email: will.hopkins=AT=otago.ac.nz. Sportscience 4(1), sportsci.org/jour/0001/inbrief.html#edit, 2000 (338 words)
     First, my usual appeal for copy! If you've read a paper lately that you think breaks new ground or that needs a plain-language spin, write an item about it for this In-brief page. More substantial articles are always welcome, too. Click here for more info.
     Here are some useful new links that you might otherwise miss on our Links and other pages:

     My main contribution to this issue is an extensive update of an article on quantitative research design. It includes a better account of why and how you should include subject characteristics in your design and analysis.
     Thanks to the other people who have contributed to this issue: Ken Daley for his regular compendium of links and info in Moving Together, Pete Pfitzinger for a first-hand account of the annual altitude symposium, Andy Doyle for dotting the V; thanks also to our reviewers (Ben Levine, Greg Atkinson, Matt Kerner) and co-webmaster (Matt Kerner).


VITAMIN C WARNING
Will G Hopkins PhD, Physiology and Physical Education, University of Otago, Dunedin 9001, New Zealand. Email: will.hopkins=AT=otago.ac.nz. Sportscience 4(1), sportsci.org/jour/0001/inbrief.html#vitC, 2000 (142 words)
     Many people take megadoses of vitamin C in the hope that its anti-oxidant properties will speed recovery from the muscle damage of hard training. Large doses of vitamin C are also known to reduce the severity of symptoms of colds and flu. But a recent issue of NewScientist (11 March, p.21) featured a short item on a potential danger of vitamin C supplementation. At a conference of the American Heart Association in San Diego in March, James Dwyer reported that healthy middle-aged men and women consuming a typical megadose of 500 mg of a vitamin C supplement every day had 2.5 times as much thickening of their arteries as people who took no supplement. We should wait until the paper is published before jumping to conclusions, but in the meantime get your vitamin C in smaller doses the natural way: in fresh fruit and vegetables.


CREATINE AND KIDNEY DAMAGE?
Will G Hopkins PhD, Physiology and Physical Education, University of Otago, Dunedin 9001, New Zealand. Email: will.hopkins=AT=otago.ac.nz. Sportscience 4(1), sportsci.org/jour/0001/inbrief.html#creatine, 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
For recent reviews of creatine on the Web,
 see Incledon (2000) and Kreider (1999).  For a large collection of recent abstracts of research by Kreider et al., all showing no harmful side effects from creatine supplementation, click here.


LIABILITY FOR SIDE EFFECTS
Will G Hopkins PhD, Physiology and Physical Education, University of Otago, Dunedin 9001, New Zealand. Email: will.hopkins=AT=otago.ac.nz. Sportscience 4(1), sportsci.org/jour/0001/inbrief.html#liability, 2000 (420 words)
    The possibility that vitamin C and creatine can be harmful raises the question of liability. It seems reasonable to me that the label on the supplements--or indeed on any product or service--should give a realistic warning of possible side effects. I also believe that such a warning should protect the manufacturer or supplier from litigation, unless it can be shown that there was deliberate or careless underestimation of the risk or failure to update the risk in the light of new data. I floated these ideas on the Sportscience list, using the risk of kidney damage with creatine as an example. I received many valuable replies, which the senders subsequently gave me permission to publish. Click here to view. Here is a summary of the opinions in the replies, not all of which I agree with:

  • Studies to date have not eliminated the possibility of a low but real risk of side effects with use of creatine.
  • An informative label would still not protect the manufacturer, and would even harm the manufacturer.
  • It is unrealistic to expect to see such labels on everyday items.
  • It is difficult to link rare side effects to the use of a supplement.
  • There are industry standards for safety warnings.
  • Researchers should be liable for promoting use of ergogenic aids that have harmful side effects.
  • Creatine could in principle promote growth of tumors.
  • Over-the-counter products should be used at your own risk.
  • You can't make sensible estimates of low risk.
  • There is no evidence of harmful side effects with creatine.

    After reading these replies, I am confident that the consumer and the manufacturer would be well served by a statutory warning of side effects. It should be possible to estimate the maximum odds of rare side effects to an accuracy of an order of magnitude, on the basis of clinical trials and case studies. Most estimates of the risk of long-term effects would be high, reflecting the lack of data from long-term studies.
     See below for the sort of warning I believe we need. I did not consult any industry standards for this example, so please regard it only as a concept. I have based the example on risks from use of an imaginary amino-acid supplement, glucamine dihydrate. I have included risk of injury or death from an everyday activity, to help consumers interpret the risks. I have also included the website of an imaginary government agency that would control risk assessment.

Statutory Warning of Side Effects for: Glucamine Dihydrate

  • Use this product at your own risk. This warning protects the manufacturer and any agent from litigation for any harmful side effects.
  • Serious inflammation of kidneys: known odds are 1:10,000 after one month of use; odds are 1:10 for anyone with an existing kidney problem.
  • All other harmful side effects: none confirmed by 04/31/00; odds are at most 1:1000 after one month of use, 1:100 after one year of use, and 1:10 after 10 years of use.
  • For comparison, odds are 1:1000 for serious injury or death from one year of average car use in the US.
  • Visit http://ConsumerRisk.org for updates of risk of side effects.

2000
Published April 2000