More indepth view on Creatine

glock40_1979

Douglas Kalman MS, RD, CCRC

Creatine monohydrate has been used as
an ergogenic aid since the early 1970’s6.
In the United States, the use of creatine
monohydrate surged in the 1990’s. This also correlated with
scientific evidence demonstrating that supplemental creatine
monohydrate has ergogenic (performance enhancing) properties
in athletes2, 3. One recent survey indicated that 37.5% of male
college athletes use creatine monohydrate1. By virtue of its sales
and known efficacy, it is the most popular dietary supplement
among strength athletes today.

Creatine is found in the diet and can be synthesized by the liver,
pancreas, and kidneys. The daily turnover of creatine monohydrate
is about 2 g for a 70 kg person. The body will synthesize about
one-half of a person’s daily creatine needs from amino acids. The
remaining daily need of creatine is obtained from the diet. Meat
or fish are the best natural sources. For example, there is about 1
g of creatine in 250 g (half a pound) of raw meat. However the
primary way that athletes “load” the muscle with creatine is
through supplementation with synthetic creatine monohydrate.

Review of the Science

Creatine exists in the body in free and in phosphorylated forms
(phosphocreatine/creatine phosphate). Creatine is mostly stored
in muscles (95%) where it is used as a buffer. When we exercise
there is a concomitant increase in the need for energy. During
increased energy demands, phosphocreatine provides phosphate to
adenosine diphosphate (ADP) to produce adenosine triphosphate
(ATP), the body’s energy currency. Exercise that demands short
bursts of energy relies upon both ATP and phosphocreatine for
energy.

Figure one denotes when during exercise creatine is most needed5.
Supplementing with creatine monohydrate will increase creatine
phosphate stores (as well as circulating creatine levels). Thus the
person who uses creatine monohydrate and exercises at high
intensity will have the “extra” creatine readily available so that
the body can exercise harder and recover quicker.

Creatine monohydrate has typically been used by both athletes
and in research by including loading and maintenance doses.
Loading is the ingestion of a total of 20 grams per day for five to
seven days. This format will increase muscle creatine levels by
about 25%3, 4. Recent research has found that a daily creatine
monohydrate dose of 2 grams over a 30-day period will result in
the same amount of muscle creatine content increase as a five-day
loading period8. Thus there may not be a need to creatine
monohydrate load and to take maintenance doses (typically 5
grams daily) if a person does not have an immediate need to do so.

Muscle creatine monohydrate absorption and uptake is mainly
mediated by the initial creatine content of the muscle3, 4. Subjects
with the lowest muscle creatine levels absorb the greatest amount of
creatine monohydrate, and it appears that creatine monohydrate
absorption is enhanced when combined with ~50 grams of a
carbohydrate/protein combination.

Creatine monohydrate supplementation appears to be less effective
in the following situations:
• When less than 20 g per day is used for 5 days or less
(no loading).
• When low doses (2 – 3 g per day) are used without an
initial high-dose loading period.
• In crossover studies with insufficient time (less than
5 weeks) to allow washout of the creatine.
• And when repeated sprints were performed with very
short or very long recovery periods between sprints.

It is also possible that subject variability in response to creatine
monohydrate supplementation may account for the lack of
ergogenic benefit reported in these studies. Consequently, although
most studies indicate that creatine monohydrate supplementation
may improve performance, creatine monohydrate supplementation
may not provide ergogenic value for everyone.

In controlled laboratory studies, oral creatine monohydrate
supplementation has been shown to be ergogenic in repeated
stationary cycling sprints, weight training, repetitive muscle
contractions such as knee extensions, kayak ergometry, swimming,
and rugby. These positive studies may not have application to all
forms of sports, but one should realize the ergogenic effect of creatine
monohydrate might only be in those types of sports that last
between two seconds and 90 seconds, or involving repeated bouts.

Side Effects and Concerns

The only side effect reported from clinical studies in preoperative
and post-operative patients, untrained subjects, and elite athletes
has been weight gain. However, a number of concerns about possible
side effects of creatine monohydrate supplementation have
been mentioned in lay publications, supplement advertisements,
and on the Internet. It should be noted that these claims of
“unsafe” have not been substantiated in any prospective creatine
monohydrate study. Unfortunately, many of these concerns have
recently received significant media coverage thus they are worthy
of discussion.

Since creatine is an amino acid, it has been suggested that creatine
monohydrate supplementation may affect kidney and/or liver
function. However, no studies have reported clinically significant
elevations in kidney function markers or liver enzymes in response
to creatine monohydrate supplementation. No study has found
that creatine monohydrate supplementation has any negative
effects on athletes (medical markers of safety) who participate in
outdoor summer-type sports.

There have been some reports that creatine monohydrate
supplementation may promote a greater incidence of muscle
strains or pulls. No study however has found this to be true7.

Conclusion

To date, there are over 500 studies on this ergogenic aid. Current
thought includes using creatine monohydrate to augment gains
in muscle size and strength9. Short-term creatine monohydrate
supplementation (e.g. 20 g/day for 5 – 7 days) has typically been
reported to increase total creatine content by 10 – 30% and
phosphocreatine stores by 10 – 40%. In addition creatine monohydrate
supplementation has been reported to improve maximal
power/strength (5 – 15%), work performed during sets of
maximal effort muscle contractions (5 – 15%), single-effort
sprint performance (1 – 5%), and work performed during
repetitive sprint performance (5 – 15%).

Creatine monohydrate supplementation during training has been
reported to promote significantly greater gains in strength, fat
free mass, and performance primarily of high intensity exercise
tasks. Not all of the studies examining athletic uses demonstrate
an ergogenic effect; approximately 30% do not support the agent,
although some report non-significant positive effects or influence
of creatine monohydrate. Future research will determine what
dose may be best for athletic uses.
Nsca Stength and Conditioning Journal Article