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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.
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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.
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Statutory Warning of
Side Effects for: Glucamine Dihydrate
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- 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.
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©2000
Published April 2000
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