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Beth Lulinski, M.S., R.D.
Creatine is marketed as "nature's muscle builder"
and "the most legitimate sports supplement around."
Professional and amateur athletes alike are gobbling up this alleged
ergogenic aid, hoping to increase their strength and performance.
Creatine supplementation is claimed to increase muscle power by
playing a role in the transfer of energy to help the muscle contract.
Supplement labels state that "creatine is converted to phosphocreatine,
which is important for short energy bursts such as sprinting and
weight lifting" and that "depletion of phosphocreatine
can result in muscle fatigue and fading muscle power." Claims
are also made that supplementation increases muscle body mass.
Health-food stores sell creatine supplements in capsule, chewable,
and powdered form, the most popular being the powder. One teaspoon
of powder contains 5 grams (g) of creatine monohydrate. The recommended
daily dose is 1-2 teaspoons dissolved in 8 ounces of water or
sweetened beverage. Manufacturers and distributors suggest a five-
to seven-day loading phase with intake of 10-20 g (2-4 scoops)
daily to fill up the muscle. The maintenance phase of 5-10 g/day
is recommended before and/or immediately following a workout.
This protocol is claimed to increase creatine muscle stores by
Role In Muscle Contraction
To meet the demands of a high-intensity exercise, such as a
sprint, muscles derive their energy from a series of reactions
involving adenosine triphosphate (ATP), phosphocreatine (PCr),
adenosine diphosphate (ADP), and creatine. ATP, the amount of
which is relatively constant, provides energy when it releases
a phosphate molecule and becomes ADP. ATP is regenerated when
PCr donates a phosphate molecule that combines with ADP. Stored
PCr can fuel the first 4-5 seconds of a sprint, but another fuel
source must provide the energy to sustain the activity. Creatine
supplements increase the storage of PCr, thus making more ATP
available to fuel the working muscles and enable them to work
harder before becoming fatigued .
The body's pool of creatine can be replenished either from
food (or supplements) or through synthesis from precursor amino
acids. Dietary sources include beef, tuna, cod, salmon, herring,
and pork . The normal dietary intake of creatine is 1-2 g/day,
although vegetarians may consume less [3,4]. Dietary creatine
is absorbed from the intestines into the bloodstream. If the dietary
supply is limited, creatine can be synthesized from the body stores
of the amino acids glycine, arginine, and methionine. The kidneys
use glycine and arginine to make guanidinoacetate, which the liver
methylates to form creatine , which is transported to the muscle
cells for storage. It is also stored in the kidneys, sperm cells,
and brain tissue .
The maximum amount of creatine the body can store is about
0.3 gram per kilogram of body weight . The creatine content
of skeletal (voluntary) muscles averages 125 millimoles per kilogram
of dry matter (mmol/kg/dm) and ranges from about 60 to 160 mmol/kg/dm.
Approximately 60% of muscle creatine is in the form of PCr. Human
muscle seems to have an upper limit of creatine storage of 150
to 160 mmol/kg/dm. Athletes with high creatine stores don't appear
to benefit from supplementation, whereas individuals with the
lowest levels, such as vegetarians, have the most pronounced increases
following supplementation. Without supplementation, the body can
replenish muscle creatine at the rate of about 2 g/day .
Although creatine is a natural component of food, the amount
of food required to supersaturate the muscle with PCr may not
be feasible. For example, it could require 22 pounds of meat daily
. If creatine monohydrate is proven to be a safe and effective
ergogenic aid, creatine supplementation may be the simplest way
to increasing muscle stores. It may be beneficial to avoid caffeine
if taking creatine supplements. One study showed that caffeine
diminished strength gains seen with creatine use .
Evidence Supporting Use
Several studies support the use of creatine supplementation
for enhancing activities that require short periods of high-intensity
power and strength. These include weightlifting, sprinting, and
- One study demonstrated that daily supplementation with 5
g of creatine monohydrate increased the intracellular creatine
and PCr content of quadriceps muscle in 17 human subjects. Those
with the lowest initial total creatine content had the greatest
increase. In addition, exercise enhanced creatine uptake in muscle.
No adverse effects were reported .
- Another study found that one week of creatine supplementation
at 25 g/day enhanced muscular performance during repeated sets
of bench press and jump squat exercise. Creatine supplementation
appeared to allow the subjects to complete their workouts at
a higher intensity. The researchers concluded that, over time,
working at higher intensities may provide a more intense training
stimulus and improved muscular adaptations .
- Another study demonstrated that females receiving 4 days
of high-dose creatine intake (20 g/day) followed by low-dose
creatine intake (5 g/day) during 10 weeks of resistance training
(3hours/week) increased muscle PCr concentrations by 6%. Also,
maximal strength of the muscle groups trained increased by 20-25%,
maximal intermittent exercise capacity of the arm flexors increased
by 10-25% and fat-free mass increased by 60% .
- A double-blind study provided 20 g/day of creatine monohydrate
for 5 days to qualified sprinters and jumpers who performed 45
seconds of continuous jumping and 60 seconds of continuous treadmill
running. Supplementation enhanced performance in the jumping
test by 7% for the first 15 seconds and 12% for the next 15 seconds,
but there was no difference for the final 15 seconds. There was
a 13% improvement in the time of intensive running to exhaustion
- Another double-blind study supplemented with 18.75 g/day
of creatine monohydrate for 5 days prior to high-intensity intermittent
work to exhaustion, and then 2.25 g/day during testing. The workouts
consisted of cycling to exhaustion using several protocols: (a)
nonstop, (b) 60 seconds work/120 seconds rest, (c) 20 seconds
work/40 seconds rest, and (d) 10 seconds work/20 seconds rest.
Creatine supplementation significantly increased the total work
time for all four protocols .
- Another study tested male subjects performing two bouts of
30 second isokinetic cycling before and after ingesting 20 g
creatine monohydrate daily for 5 days. Work production improved
about 4%. Cumulative increases in both peak and total work production
over the two exercise bouts were positively correlated with the
increase in muscle creatine .
- A 12-week placebo-controlled study of 19 weightlifters in
their mid-twenties found that the creatine group could lift more
weight and had greater increases in fat-free mass and muscle-fiber
size than did the placebo group. The researchers thought that
the creatine let the athletes who used it train harder .
- Three additional studies suggest that creatine supplementation
may not be beneficial for running velocity, sprint swimming performance,
or a maximal cycling effort . Short bouts of repeated anaerobic
activity have shown some potential benefits with creatine supplementation
use in a laboratory setting. However, creatine supplementation
has not been shown to enhance single-event performance such as
stationary cycling [16-19]. Taken together, these studies do
not support creatine supplementation to enhance aerobic activities
such as distance running.
Other areas of research include therapeutic uses of creatine
to help patients with muscle wasting caused by disease states
such as muscular dystrophy and amyotrophic lateral sclerosis (ALS).
Small-scale preliminary studies show some gains in strength may
be possible for these patients, which could improve their quality
of life. One study of 81 patients with various neurologic diseases
found that giving 10 g/day of creatine for five days, followed
by 5 grams for another week, increases their muscle strength by
about 10% . Large-scale studies should be done before recommendations
are made to such patients.
Creatine supplementation often causes weight gain that can
be mistaken for increase in muscle mass. Increasing intracellular
creatine may cause an osmotic influx of water into the cell because
creatine is an osmotically active substance . It is possible
that the weight gained is water retention and not increased muscle.
The retention of water may be connected to reports of muscle cramps,
dehydration, and heat intolerance when taking creatine supplements.
It would be prudent to encourage proper hydration for creatine
users. Further research is needed to investigate these and other
possible side effects.
Creatine is classified as a "dietary supplement"
under the 1994 Dietary Supplement Health and Education Act and
is available without a prescription. Creatine is not subjected
to FDA testing, and the purity and hygienic condition of commercial
creatine products may be questionable . A 1998 FDA report
lists 32 adverse creatine-associated events that had been reported
to FDA. These include seizure, vomiting, diarrhea, anxiety, myopathy,
cardiac arrhythmia, deep vein thromboses and death. However, there
is no certainty that a reported adverse event can be attributed
to a particular product . A recent survey of 28 male baseball
players and 24 male football players, ages 18 to 23, found that
16 (31%) experienced diarrhea, 13 (25%) experienced muscle cramps,
7 (13%) reported unwanted weight gain, 7 (13%) reported dehydration,
and 12 reported various other adverse effects .
There appears to be some potential for creatine supplementation.
However, many questions remain. Are there any long-term harmful
effects from supplementation? Is there a point where enhanced
performance levels off from long-term supplement usage? What effect
does "stacking" or taking two ergogenic aids simultaneously
have on the body? What happens if you immediately stop taking
the creatine supplement? Is the enhanced performance great enough
to warrant the expense of the supplement? Until further research
answers these questions, creatine is not recommended for the average
For Additional Information
- Jenkins, MA. Creatine
supplementation in athletes: Review
- Creatine is the object of intensive research. To keep current,
use the links below to visit the abstracts on PubMed and click
on "Related Articles" when you arrive.
- Murray RK and others. Harper's Biochemistry, 24th Edition.
Stamford, CT: Appleton & Lange, 1996.
- Sahelian R, Tutle D. Creatine: Nature's Muscle Builder. Garden
City, NY: Avery Publishing Group, 1997.
- Toler S. Creatine
is an ergogen for anaerobic exercise. Nutrition Reviews 55:21-25,
- Maughan R. Creatine
supplementation and exercise performance. International Journal
of Sport Nutrition 5:94-101, 1995.
- Harris RC, Soderlund K, Hultman E. Elevation
of creatine in resting and exercised muscle of normal subjects
by creatine supplementation. Clinical Science 83:367-374,
- Haff GG, Potteiger JA. Creatine supplementation for the strength/power
athlete. Strength and Conditioning 19(6):72-74, 1997.
- Coleman E. Creatine
monohydrate: a sprint performance enhancer?
HCRC Web site.
- Modica P. Creatine supplements show some sports benefit.
Medical Tribune News Service. July 10, 1997.
- Vandenberghe K and others. Caffeine
counteracts the ergogenic action of muscle creatine loading.
Journal of Applied Physiology 80:452-457, 1996.
- Volek JS and others. Creatine
supplementation enhances muscular performance during high-intensity
resistance exercise. Journal of American Dietetic Association
- Vandenberghe K and others. Long-term
creatine intake is beneficial to muscle performance during resistance
training. Journal of Applied Physiology 83:2055-2063, 1997.
- Bosco C and others. Effect
of oral creatine supplementation on jumping and running performance.
International Journal of Sports Medicine 18:369-372, 1997.
- Prevost MC, Nelson AG, Morris GS. Creatine
supplementation enhances intermittent work performance. Research
Quarterly for Exercise and Sport 68:233-240, 1997.
- Casey A and others. Creatine
ingestion favorably affects performance and muscle metabolism
during maximal exercise in humans. American Journal of Physiology
- Volek JS and others. Performance
and muscle fiber adaptations to creatine supplementation and
heavy resistance training. Medicine and Science in Sports
and Exercise 31:1147-1156, 1999.
- Dawson B and others. Effects
of oral creatine loading on single and repeated maximal short
sprints. Australian Journal of Science and Medicine in Sport
- Cooke WH, Grandjean PW, Barnes WS. Effect
of oral creatine supplementation on power output and fatigue
during bicycle ergometry. Journal of Applied Physiology 78:670-673,
- Odland LM and others. Effect
of oral creatine supplementation on muscle [Pcr] and short-term
maximum power output. Medicine and Science in Sports and
Exercise 29:216-219, 1997.
- Snow RJ and others. Effect
of creatine supplementation on sprint exercise performance and
muscle metabolism Journal of Applied Physiology 84:1667-1673,
- Tarnopolsky M. Creatine
monohydrate increases strength in patients with neuromuscular
diseases. Neurology 52:854-857, 1999.
- Sorgen C. Creatine supplementation: The quest for power performance.
Today's Dietitian (1)3:26-29, 1999.
Special Nutritionals Adverse Event Monitoring System. Accessed
June 7, 1999.
- Juhn MS and others. Oral
creatine supplementation in male collegiate athletes: A survey
of dosing habits and side effects. Journal of the American
Dietetic Association 99:593-594, 1999.
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This article was posted on 9/17/99.
- Ms. Lulinski is a medical nutritionist. Susan Moore, MS,
RD, Susan Parry Mandell, MS, RD, Thomas J. Wheeler, PhD, and
Manfred Kroger, PhD, also helped produce this article.