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There have been numerous studies examining whether creatine
supplementation may carry adverse effects on users. Many published studies seem
questionable due to small sample sizes.
Effects on renal function: Poortmans and Francaux
compare 9 individuals taking 1 to 80 g/d from 10 months to 5 years with 85
control subjects who were not taking creatine. There were no differences between
the groups in plasma creatine, creatinine, urea, or albumin. The creatine-supplemented
group had an increase in urinary creatine excretion and urinary
creatine:creatinine ratio. The glomerular filtration rate (measured by
creatinine clearance), glomerular membrane permeability (measured by albumin
clearance), and tubular reabsorption (measured by urea clearance) were normal in
both groups.
In another study, Poortmans et al. studied 5 healthy
men who ingested 20 g creatine or placebo. They found that creatine-supplemented
individuals had an increased arterial content and urinary excretion rate of
creatine. However, arterial and urinary creatinine was unchanged. They concluded
that short-term creatine supplementation does not have any detrimental effects
on renal responses of healthy men.
Taes et al. used an animal model to examine
whether 0.9 g creatine per kg body weight would adversely affect rats that were
2/3 nephrectomized as opposed to rats with normal renal function. They concluded
that creatine supplementation for 4 weeks does not impair kidney function in
rats with preexisting renal failure.
Effects on hepatic function: In an animal study,
Duarte et al. demonstrated that mice that were fed creatine for 6 days
had a 23% increased hepatic protein content, and liver phosphocreatine was also
increased. They demonstrated decreased AST and increased ALT levels.
Waldron et al. studied 8 subjects who used creatine
supplements while participating in 5 weeks of high intensity exercise. They
reported no changes in ALT, AST, alkaline phophatase, BUN, albumin, creatinine,
or direct or total bilirubin.
Robinson et al. studied 48 individuals who used
creatine supplementation for 5 days to 9 weeks. They noted that serum creatinine
was slightly elevated the day after supplementation. They concluded that there
was no evidence of hematological, hepatic, or muscle damage using serum markers.
Effects on anterior compartment pressure: Potteiger et al. demonstrated that creatine supplementation was associated with
incresed anterior compartment pressure of the distal legs before, during, and
after exercise in 16 physically active college-aged males after 35 days of
creatine use. After 28 days without supplementation, anterior compartment
pressures began to trend downwards towards normal values. |
