Posted by Creatine monhydrate on June 22, 1999 at 11:42:45:
Journal of the American Dietetic Association, May 1999 v99 i5 p593(3)
Oral creatine supplementation in male collegiate athletes: a survey of dosing
habits and
side effects. Mark S. Juhn; John W. O'Kane; Debra M. Vinci.
Abstract: The occurrence of adverse side effects, such as muscle cramping,
weight gain and diarrhea, was
reported on athletes taking
greater-than-recommended doses of creatine supplementation. Muscle
cramping
occurs as creatine supplementation promotes water retention in the
skeletal muscle. Such property can also be
attributed to the occurrence of
weight gain among people taking larger doses of creatine. Diarrhea occurs
as
creatine supplementation places an unusually high osmotic load on the
digestive system.
Full Text: COPYRIGHT 1999 American Dietetic Association
Although its efficacy in running, swimming, and nonlaboratory settings is
inconclusive (1), creatine has become
very popular among athletes. Some
laboratory studies have shown oral creatine supplementation to be
ergogenic
in repeated stationary cycling sprints (2-5) and weight lifting
(47), but not in single-cycle sprints (3,810). There is
concern, however,
that some athletes exceed recommended doses, which may unnecessarily increase
the risk of
adverse side effects.
The purpose of this study was to determine if athletes exceed recommended
doses and to report on commonly
perceived side effects. Athletes were also
asked to cite their primary source of information regarding
creatine
supplementation. We hope this study can provide [TABULAR DATA
OMITTED] dietitians with the data to
make a greater impact on athletes and
their nutritional practices.
Creatine is a nitrogenous amino acid derivative found naturally in skeletal
muscle, heart muscle, the brain, testes,
and other organs (11). Human beings
endogenously synthesize 1 g creatine per day, primarily via the liver
and
pancreas, and consume 1 to 2 g creatine per day in a normal
meat-and-fish-eating diet (12). The highest
concentrations of creatine are
found in herring, salmon, tuna, pork, and beef, although degradation of
creatine
occurs with cooking (1,12). Creatine used for supplementation is
made synthetically, and the usual recommended
regimen is a loading phase of
20 g/day for 5 days, followed by a maintenance dose of 2 to 5 g/day
(1,12,13).
However, 2 g/day has been shown to be sufficient for maintenance
(13).
MATERIALS AND METHODS
Twenty-eight male baseball players and 24 male football players from a
National Collegiate Athletic Association
(NCAA) Division I school were
surveyed. All voluntarily took creatine supplements. They ranged in age from
18
to 23 years, and in weight from 165 to 335 lb (75 to 152 kg). Players who
took other forms of supplementation
were excluded. All players consumed the
same powder form of creatine supplied by staff of the school's training
room.
The powder was dissolved in water or a glucose solution and consumed in divided
doses throughout the
day. The baseball players took creatine supplements for
5 months of the year and football players for 3 months,
primarily during
off-season training periods.
Survey questions covered duration and dosage of creatine consumption,
participants' primary source of
information regarding creatine
supplementation, and perceived side effects. The question on side effects
was
open-ended; possible side effects were not listed. Also, because weight
gain is an established side effect (12-14),
players were asked to cite weight
gain only if they thought it impaired their performance. Finally, athletes
were
asked if they would take creatine again.
RESULTS
Side Effects
The Table lists the side effects experienced by the subjects. Diarrhea was
the most frequently reported adverse
effect, followed by muscle cramping,
although only 2 athletes reported a sprain or tear. Seven athletes
considered
the weight gain to be a "negative" side effect, and 7 athletes
complained of dehydration. Fourteen subjects
reported no perceived side
effects.
Dosage
All players initiated creatine usage with a loading dose of 20 to 30 g/day
for 5 to 7 days. Of the 52 athletes, 39
exceeded the recommended maintenance
dose of 2 to 5 g/day, the most common dosage being 6 to 8 g/day
(Table).
Eighteen players took 9 g or more per day for maintenance, and 3 players took 17
to 20 g/day for
maintenance.
Primary Source of Information
Forty-five respondents cited their strength and conditioning coach as their
primary source of information regarding
creatine (Table). Four athletes named
themselves, and 1 cited a dietitian.
Satisfaction
Forty athletes stated that they plan to continue using creatine or would use
creatine again (Table). This included
22 of the 28 baseball players and 18 of
the 24 football players.
DISCUSSION
Our survey supports anecdotal reports that some athletes take
greater-than-recommended doses of creatine.
Hultman et al (13) demonstrated
that a maintenance dose of 2 g/day, or more specifically 0.03 g/kg per day,
is
sufficient to maintain the maximum muscle concentration of creatine
(150-160 mmol/kg) achieved by the loading
phase. Larger doses are therefore
unnecessary and may increase the risk of adverse side effects. A case report
of
interstitial nephritis in a previously healthy 20-year-old man revealed
that he had been taking 20 g creatine daily
for 4 weeks (14).
The strength and conditioning coach acknowledged that some athletes
self-prescribe supplements and take
higher-than-recommended doses. Dosage is
one area in which a dietitian's input would have been helpful. In
addition,
the fact that 45 of 52 respondents cited the strength coach as their primary
source of information
underscores the importance of the dietitian's
communication with coaches and players.
Muscle cramping has been anecdotally reported and may be related to the water
retention in skeletal muscle that
occurs with creatine supplementation
(6,13,15). Theoretically, staying well-hydrated may reduce this
risk,
although to our knowledge no studies have been done to substantiate or
refute this. The weight gain from this
water retention may be the reason why
several studies of runners (16-18) and swimmers (19-21) have not
demonstrated
an ergogenic effect. The diarrhea observed in our study may be the result of the
unusually high
osmotic load placed on the digestive system of some subjects.
A review of potential side effects of creatine supplementation (15) found no
causal relationship with
gastrointestinal symptoms or muscle dysfunction,
although none of the studies reviewed involved sample sizes
greater than 12
for the creatine group. The larger concern lies in the unknown risks of
long-term use. Still, the
adverse effects reported in our study may be due to
placebo effect, product impurities, or excessive dosing.
Double-blind
randomized studies with large sample sizes would help clarify this.
Despite the fact that 38 of the respondents experienced at least I
undesirable side effect, only 12 stated they
would not take creatine again,
suggesting that the perceived benefit outweighed the adverse effects.
However,
expectation can influence perception, and had the strength coach not
encouraged creatine use, the favorable
reaction may have been lower.
APPLICATIONS
Dietetics professionals can play an important role in the nutritional
practices of athletes. Dietitians should
communicate with coaches and
players, as many players use their strength coach for nutrition advice.
Strength
and conditioning coaches are often in a position to receive
supplements and endorse products, so having a
dietitian's input in purchasing
and distributing supplements would help ensure proper handling of such
procedures.
Unfortunately, dietitians who work in athletics are often hired
part-time or as consultants, which provides an
additional challenge to their
ability to influence athletes effectively. Our study demonstrates the need for
dietetics
professionals to become more involved in the decision-making
processes of athletic nutrition.
The authors thank Rick Huegli for his assistance.
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M.S. Juhn is a clinical instructor in the Department of Family Medicine at
the University of Washington School of
Medicine and a staff physician for the
Hall Health Primary Care Center Sports Medicine Clinic, University
of
Washington, Seattle. J. W. O'Kane is an assistant professor in the
Department of Orthopedics, an adjunct
assistant professor in the Department
of Family Medicine, and a team physician for intercollegiate athletics at
the
University of Washington. D.M. Vinci is director of health education and
nutrition services at Hall Health Primary
Care Center and a former sports
nutritionist for University of Washington intercollegiate athletics.
Article A54772587