Jacques Poortmans

Long-term oral creatine supplementation does not impair renal function in healthy athletes

PURPOSE Oral creatine supplementation is widely used in sportsmen and women. Side effects have been postulated, but no thorough investigations have been conducted to support these assertions. It is important to know whether long-term oral creatine supplementation has any detrimental effects on kidney function in healthy population. METHODS Creatinine, urea, and plasma albumin clearances have been determined in oral creatine consumers (10 months to 5 yr) and in a control group. RESULTS There were no statistical differences between the control group and the creatine consumer group for plasma contents and urine excretion rates for creatinine, urea, and albumin. Clearance of these compounds did not differ between the two groups. Thus, glomerular filtration rate, tubular reabsorption, and glomerular membrane permeability were normal in both groups. CONCLUSIONS Neither short-term, medium-term, nor long-term oral creatine supplements induce detrimental effects on the kidney of healthy individuals.

Exercise and Renal Function

SummaryExercise induces profound changes in the renal haemodynamics and in electrolyte and protein excretion. Effective renal plasma flow is reduced during exercise. The reduction is related to the intensity of exercise and renal blood flow may fall to 25% of the resting value when strenuous work is performed. The combination of sympathetic nervous activity and the release of catecholamine substances is involved in this process. The reduction of renal blood flow during exercise produces a concomitant effect on the glomerular filtration rate, though the latter decreases relatively less than the former during exertion. However, the degree of hydration has an important influence on the glomerular filtration rate. An antidiuretic effect is observed during intense exercise. Changes in urine flow are dependent on the plasma antidiuretic hormone levels which are increased by intense exercise.Heavy exercise has an inhibitory effect on most electrolytes (Na, CI, Ca, P). With potassium, however, most studies report that potassium excretion is not consistently affected by moderate to heavy exercise. Increased aldosterone production helps the body to maintain sodium by increasing its reabsorption from the filtered tubular fluid. Recent studies suggest that sympathetic stimulation may be involved during exercise. Strenuous work leads to an increased excretion of erythrocytes and leucocyctes in urine. Cylindruria has been regularly found in postexercise urine in different sports.Postexercise proteinuria is a common phenomenon in humans. It seems to be directly related to the intensity of exercise, rather than to its duration. This excretion of proteins in urine is a transient state with a half-time of approximately I hour. Postexercise proteinuria has a pattern different from normal physiological proteinuria. Immunochemical techniques demonstrate that postexercise proteinuria is of the mixed glomerular-tubular type, the former being predominant. The increased clearance of plasma proteins suggests an increased glomerular permeability and a partial inhibition of tubular reabsorption of macromolecules.Haemoglobinuria and myoglobinuria may be observed under special exercise conditions. The degree of hydration appears to be important to reduce these abnormalities.

Effect of short-term creatine supplementation on renal responses in men.

Abstract There is an increasing utilisation of oral creatine (Cr) supplementation among athletes who hope to enhance their performance but it is not known if this ingestion has any detrimental effect on the kidney. Five healthy men ingested either a placebo or 20 g of creatine monohydrate per day for 5 consecutive days. Blood samples and urine collections were analysed for Cr and creatinine (Crn) determination after each experimental session. Total protein and albumin urine excretion rates were also determined. Oral Cr supplementation had a significant incremental impact on arterial content (3.7 fold) and urine excretion rate (90 fold) of this compound. In contrast, arterial and urine Crn values were not affected by the Cr ingestion. The glomerular filtration rate (Crn clearance) and the total protein and albumin excretion rates remained within the normal range. In conclusion, this investigation showed that short-term oral Cr supplementation does not appear to have any detrimental effect on the renal responses of healthy men.

Adverse effects of creatine supplementation: Fact or fiction?

The consumption of oral creatine monohydrate has become increasingly common among professional and amateur athletes. Despite numerous publications on the ergogenic effects of this naturally occurring substance, there is little information on the possible adverse effects of this supplement. The objectives of this review are to identify the scientific facts and contrast them with reports in the news media, which have repeatedly emphasised the health risks of creatine supplementation and do not hesitate to draw broad conclusions from individual case reports.Exogenous creatine supplements are often consumed by athletes in amounts of up to 20 g/day for a few days, followed by 1 to 10 g/day for weeks, months and even years. Usually, consumers do not report any adverse effects, but body mass increases. There are few reports that creatine supplementation has protective effects in heart, muscle and neurological diseases. Gastrointestinal disturbances and muscle cramps have been reported occasionally in healthy individuals, but the effects are anecdotal. Liver and kidney dysfunction have also been suggested on the basis of small changes in markers of organ function and of occasional case reports, but well controlled studies on the adverse effects of exogenous creatine supplementation are almost nonexistent.We have investigated liver changes during medium term (4 weeks) creatine supplementation in young athletes. None showed any evidence of dysfunction on the basis of serum enzymes and urea production. Short term (5 days), medium term (9 weeks) and long term (up to 5 years) oral creatine supplementation has been studied in small cohorts of athletes whose kidney function was monitored by clearance methods and urine protein excretion rate. We did not find any adverse effects on renal function.The present review is not intended to reach conclusions on the effect of creatine supplementation on sport performance, but we believe that there is no evidence for deleterious effects in healthy individuals. Nevertheless, idiosyncratic effects may occur when large amounts of an exogenous substance containing an amino group are consumed, with the consequent increased load on the liver and kidneys. Regular monitoring is compulsory to avoid any abnormal reactions during oral creatine supplementation.

The Effect of Exercise on Visceral Adipose Tissue in Overweight Adults: A Systematic Review and Meta-Analysis

Excessive visceral adipose tissue appears to trigger a cascade of metabolic disturbances that seem to coexist with ectopic fat storage in muscle, liver, heart and the ß-cell. Therefore, the reduction of visceral adipose tissue potentially plays a pivotal role in the treatment of the metabolic syndrome. The purpose of this systematic review and meta-analysis is to describe the overall effect of exercise on visceral adipose tissue and to provide an overview of the effect of different exercise regimes, without caloric restriction, on visceral adipose tissue in obese persons. A systematic literature search was performed according to the PRISMA statement for reporting systematic reviews and meta-analyses. The initial search resulted in 87 articles after removing duplicates. After screening on title, abstract and full-text 15 articles (totalling 852 subjects) fulfilled the a priori inclusion criteria. The quality of each eligible study was assessed in duplicate with “The Critical Review Form for Quantitative Studies”. Using random-effects weights, the standardized mean difference (Hedges g) of the change in visceral adipose tissue was −0.497 with a 95% confidence interval of −0.655 to −0.340. The Z-value was −6.183 and the p-value (two tailed) was <0.001. A subgroup analysis was performed based on gender, type of training and intensity. Aerobic training of moderate or high intensity has the highest potential to reduce visceral adipose tissue in overweight males and females. These results suggest that an aerobic exercise program, without hypocaloric diet, can show beneficial effects to reduce visceral adipose tissue with more than 30 cm2 (on CT analysis) in women and more than 40 cm2 in men, even after 12 weeks.

Quantitative immunological determination of 12 plasma proteins excreted in human urine collected before and after exercise

Urine was collected from 6 healthy male adults at rest and from 20 male adults after a marathon race (25 miles). The concentrated urines were quantitatively analyzed, by single radial immunodiffusion, for their content in 12 different plasma proteins: tryptophan-rich prealbumin, albumin, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, ceruloplasmin, haptoglobin, Gc-globulin, transferrin, hemopexin, beta(2)-glycoprotein I, gammaA-globulin, and gammaG-globulin.Albumin, gammaA-globulin, and gammaG-globulin represent the major part of the plasma proteins detected in normal urine excreted by humans at rest (12, 0.5, and 2.5 mg respectively, out of a total excretion of 17.5 mg of plasma proteins per 24 hr). The other plasma proteins were excreted at a lower rate (< 0.4 mg/24 hr). The relative content of tryptophan-rich prealbumin, alpha(1)-antitrypsin, Gc-globulin, transferrin, and gammaG-globulin was lower in normal urine than in normal serum, whereas that of alpha(1)-acid glycoprotein, beta(2)-glycoprotein I, and gammaA-globulin was higher. The ratio of gammaG-globulin to gammaA-globulin was 4.9:1. When plotted on a logarithmic scale, no direct relationship between the molecular weight of a protein and the value of its renal clearance could be observed.Strenuous exercise increased (up to 50-fold) the excretion of plasma proteins which represent 82% of the total proteins found in urine, instead of 57% in urine collected from humans at rest. There was particularly a significant rise of tryptophan-rich albumin, albumin, alpha(1)-acid glycoprotein, transferrin, gammaA-globulin, and gammaG-globulin (0.26, 127, 11.8, 3.3, 1.2, and 2.0 mug respectively, out of a total excretion of 167 mug of plasma proteins per min). The ratio of gammaG-globulin to gammaA-globulin was 16:1. After exercise, the renal clearance of proteins increased from 2 to 40 times, but, as for the urine of normal subjects at rest, no direct relationship between molecular weight and renal clearance could be observed.

Biochemical changes in a 100 km run: free amino acids, urea, and creatinine.

SummaryFree amino acids, urea, and creatinine were analyzed in venous blood and urine of 11 trained (28–81 years old) male subjects before, immediately after, and 1 day after a 100 km running competition.The urinary excretion per minute of all amino acids was lowered after the contest. The renal clearance of creatinine was reduced from 116 to 60 ml/min and the clearance of most amino acids was reduced to a similar extent. However, for the amino acids with a resting clearance under 1 ml/min (x), a high relative clearance ratio (y in % of x) was seen post-exercise: y = -92.3 (log10x) +23.1, r= -0.83, showing that their high reabsorption capacity had been impaired.Serum concentrations of most free amino acids, including the branched-chain amino acids and alanine, were reduced to 35–85% of the pre-race values. The sulfur amino acids were elevated either at the end of (cystine, to 180%) or 24 h after (methionine, to 155%) the race. Urea production increased by 44% while creatinine production tended to decrease. The production of 3-methylhistidine remained unchanged. These findings are compatible with a stimulation of gluconeogenesis at the expense of the amino acid pool without induction of muscle protein catabolism.

Exploring the therapeutic role of creatine supplementation

Creatine (Cr) plays a central role in energy provision through a reaction catalyzed by phosphorylcreatine kinase. Furthermore, this amine enhances both gene expression and satellite cell activation involved in hypertrophic response. Recent findings have indicated that Cr supplementation has a therapeutic role in several diseases characterized by atrophic conditions, weakness, and metabolic disturbances (i.e., in the muscle, bone, lung, and brain). Accordingly, there has been an evidence indicating that Cr supplementation is capable of attenuating the degenerative state in some muscle disorders (i.e., Duchenne and inflammatory myopathies), central nervous diseases (i.e., Parkinson’s, Huntington’s, and Alzheimer’s), and bone and metabolic disturbances (i.e., osteoporosis and type II diabetes). In light of this, Cr supplementation could be used as a therapeutic tool for the elderly. The aim of this review is to summarize the main studies conducted in this field and to highlight the scientific and clinical perspectives of this promising therapeutic supplement.

Beneficial effects of creatine supplementation in dystrophic patients

The effect of creatine (Cr) supplementation on muscle function and body composition of 12 boys with Duchenne muscular dystrophy and three with Becker dystrophy was evaluated by a randomized double‐blind cross‐over study (3 g Cr or maltodextrin daily for 3 months, with wash‐out period of 2 months). After placebo, no change was observed in maximal voluntary contraction (MVC) and resistance to fatigue, whereas total joint stiffness (TJS) was increased by ∼25% (P < 0.05). The patients receiving Cr did not show any change in TJS, improved MVC by 15% (P = 0.02), and almost doubled their resistance to fatigue (P < 0.001). In patients still independent of a wheelchair (n = 5), bone mineral density increased by 3% (P < 0.05), and urinary excretion of collagen type I cross‐linking N‐telopeptide declined to about one third (P < 0.001) after Cr. No adverse effect was observed. Thus, Cr may provide some symptomatic benefit in these patients. Muscle Nerve 27: 604–610, 2003

Effects of training and creatine supplement on muscle strength and body mass.

Abstract The purpose of this study was to test the effect of creatine supplement on the size of the extra- and intra-cellular compartments and on the increase of isokinetic force during a strength training-program. Twenty-five healthy male subjects (age 22.0 ± 2.9 years) participated in this experiment. Seven subjects formed the control-group. They did not complete any training and did not have any dietary supplement. The eighteen other subjects were randomly divided into a creatine- (n = 8) and a placebo-group (n = 10). They were submitted to a controlled strength-training program for 42 days followed by a detraining period of 21 days. Creatine and placebo were given over a period of 9 weeks. The size of the body water compartments was assessed by bio- impedance spectroscopy and the isokinetic force was determined during a single squat by means of an isokinetic dynamometer. These measurements were completed beforehand, at the end of the training period, and after the determining period. Both placebo- and creatine-group increased the isokinetic force by about 6% after the training period, showing that creatine ingestion does not induce a higher increase of the force measured during a single movement. No change in body mass was observed in the control- and placebo-groups during the entire experiment period while the body mass of the creatine-group was increased by 2 kg (P < 0.001). This change can be attributed partially to an increase (P = 0.039) in the body water content (+1.11), and more specifically, to an increase (P < 0.001) in the volume of the inter-cellular compartment (+0.61). Nevertheless, the relative volumes of the body water compartments remained constant and therefore the gain in body mass cannot be attributed to water retention, but probably to dry matter growth accompanied with a normal water volume.