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Abstract

Creatine has been reported to be an effective ergogenic aid for athletes. However, concerns have been raised regarding the long-term safety of creatine supplementation. This study examined the effects of long-term creatine supplementation on a 69-item panel of serum, whole blood, and urinary markers of clinical health status in athletes. Over a 21-month period, 98 Division IA college football players were administered in an open label manner creatine or non-creatine containing supplements following training sessions. Subjects who ingested creatine were administered 15.75 g/day of creatine monohydrate for 5 days and an average of 5 g/day thereafter in 5-10 g/day doses. Fasting blood and 24-h urine samples were collected at 0, 1, 1.5, 4, 6, 10, 12, 17, and 21 months of training. A comprehensive quantitative clinical chemistry panel was determined on serum and whole blood samples (metabolic markers, muscle and liver enzymes, electrolytes, lipid profiles, hematological markers, and lymphocytes). In addition, urine samples were quantitatively and qualitative analyzed to assess clinical status and renal function. At the end of the study, subjects were categorized into groups that did not take creatine (n = 44) and subjects who took creatine for 0-6 months (mean 4.4 +/- 1.8 months, n = 12), 7-12 months (mean 9.3 +/- 2.0 months, n = 25), and 12-21 months (mean 19.3 +/- 2.4 months, n = 17). Baseline and the subjects' final blood and urine samples were analyzed by MANOVA and 2 x 2 repeated measures ANOVA univariate tests. MANOVA revealed no significant differences (p = 0.51) among groups in the 54-item panel of quantitative blood and urine markers assessed. Univariate analysis revealed no clinically significant interactions among groups in markers of clinical status. In addition, no apparent differences were observed among groups in the 15-item panel of qualitative urine markers. Results indicate that long-term creatine supplementation (up to 21-months) does not appear to adversely effect markers of health status in athletes undergoing intense training in comparison to athletes who do not take creatine.

Effects of acute ingestion of a pre-workout dietary supplement with and without p-synephrine on resting energy expenditure, cognitive function and exercise performance

“…Significant interactions were observed among treatments in BUN, creatinine, and BUN to creatinine ratio. As expected, PWS and PWS + S supplementation (which contained about 1.3 g of creatine) resulted in a small increase in creatinine in which values were well-within normal limits for active individuals [53, 54]. BUN and the BUN to creatinine ratio decreased indicative of less whole body catabolism.…”

“…Significant treatments x time effects were observed in total cholesterol, the ratio of CHOL: HDL and blood glucose levels. However, given that participants ingested caffeine with a small amount of maltodextrin prior to exercise, these changes were expected and within normal expected values for trained individuals undergoing intense exercise [53–56] as well as within normal clinical ranges [57]. …”

ISSN exercise & sport nutrition review: research & recommendations

“…The gains in muscle mass appear to be a result of an improved ability to perform high intensity exercise enabling an athlete to train harder and thereby promote greater training adaptations and muscle hypertrophy [72-75]. The only clinically significant side effect occasionally reported from creatine monohydrate supplementation has been the potential for weight gain [71,76-78] Although concerns have been raised about the safety and possible side effects of creatine supplementation [79,80], recent long-term safety studies have reported no apparent side effects [78,81,82] and/or that creatine monohydrate may lessen the incidence of injury during training [83-85]. Additionally a recent review was published which addresses some of the concerns and myths surrounding creatine monohydrate supplementation [86].…”

Caffeine and Creatine Use in Sport

“…If there is an increase in creatine intake and creatine stores increase, there is a proportionate increase in plasma creatinine due to the increase in delivery to a pool with a normally functioning nephron. Prospective studies using creatine for up to 5 years in healthy people [47,48,49,50] and those with disease [51,52] have uniformly shown no adverse effects of creatine supplementation on renal function. …”

“…We have found that for some reason, creatine monohydrate caused liver inflammation in mice, but not rats [54]. We and others have used γ-glutamyltransferase and bilirubin as non-muscle markers to clearly show that acute and intermediate (6 months) creatine supplementation had no effect in younger and older humans [36,43,50], or those with neurological disorders [49,52]. …”