Is It Time for a Requiem for Creatine Supplementation-Induced Kidney Failure? A Narrative Review.

Creatine has become one of the most popular dietary supplements among a wide range of healthy and clinical populations. However, its potential adverse effects on kidney health are still a matter of concern. This is a narrative review of the effects of creatine supplementation on kidney function. Despite a few case reports and animal studies suggesting that creatine may impair kidney function, clinical trials with controlled designs do not support this claim. Creatine supplementation may increase serum creatinine (Crn) concentration for some individuals, but it does not necessarily indicate kidney dysfunction, as creatine is spontaneously converted into Crn. Based on studies assessing kidney function using reliable methods, creatine supplements have been shown to be safe for human consumption. Further studies with people who have pre-existing kidney disease remain necessary.

Influence of CReatine supplementation on mUScle mass and strength after stroke (ICaRUS Stroke Trial): study protocol for a randomized controlled trial.

BACKGROUND: Stroke is a leading cause of mortality and disability, and its sequelae are associated with inadequate food intake which can lead to sarcopenia. The aim of this study is to verify the effectiveness of creatine supplementation on functional capacity, strength, and changes in muscle mass during hospitalization for stroke compared to usual care. An exploratory subanalysis will be performed to assess the inflammatory profiles of all participants, in addition to a follow-up 90 days after stroke, to verify functional capacity, muscle strength, mortality, and quality of life. METHODS: Randomized, double-blind, unicenter, parallel-group trial including individuals with ischemic stroke in the acute phase. The duration of the trial for the individual subject will be approximately 90 days, and each subject will attend a maximum of three visits. Clinical, biochemical, anthropometric, body composition, muscle strength, functional capacity, degree of dependence, and quality of life assessments will be performed. Thirty participants will be divided into two groups: intervention (patients will intake one sachet containing 10g of creatine twice a day) and control (patients will intake one sachet containing 10g of placebo [maltodextrin] twice a day). Both groups will receive supplementation with powdered milk protein serum isolate to achieve the goal of 1.5g of protein/kg of body weight/day and daily physiotherapy according to the current rehabilitation guidelines for patients with stroke. Supplementation will be offered during the 7-day hospitalization. The primary outcomes will be functional capacity, strength, and changes in muscle mass after the intervention as assessed by the Modified Rankin Scale, Timed Up and Go test, handgrip strength, 30-s chair stand test, muscle ultrasonography, electrical bioimpedance, and identification of muscle degradation markers by D3-methylhistidine. Follow-up will be performed 90 days after stroke to verify functional capacity, muscle strength, mortality, and quality of life. DISCUSSION: The older population has specific nutrient needs, especially for muscle mass and function maintenance. Considering that stroke is a potentially disabling event that can lead the affected individual to present with numerous sequelae, it is crucial to study the mechanisms of muscle mass loss and understand how adequate supplementation can help these patients to better recover. TRIAL REGISTRATION: The Brazilian Clinical Trials Registry (ReBEC) RBR-9q7gg4 . Registered on 21 January 2019.

Timing of Creatine Supplementation around Exercise: A Real Concern?

Creatine has been considered an effective ergogenic aid for several decades; it can help athletes engaged in a variety of sports and obtain performance gains. Creatine supplementation increases muscle creatine stores; several factors have been identified that may modify the intramuscular increase and subsequent performance benefits, including baseline muscle Cr content, type II muscle fibre content and size, habitual dietary intake of Cr, aging, and exercise. Timing of creatine supplementation in relation to exercise has recently been proposed as an important consideration to optimise muscle loading and performance gains, although current consensus is lacking regarding the ideal ingestion time. Research has shifted towards comparing creatine supplementation strategies pre-, during-, or post-exercise. Emerging evidence suggests greater benefits when creatine is consumed after exercise compared to pre-exercise, although methodological limitations currently preclude solid conclusions. Furthermore, physiological and mechanistic data are lacking, in regard to claims that the timing of creatine supplementation around exercise moderates gains in muscle creatine and exercise performance. This review discusses novel scientific evidence on the timing of creatine intake, the possible mechanisms that may be involved, and whether the timing of creatine supplementation around exercise is truly a real concern.

Creatine supplementation improves performance, but is it safe? Double-blind placebo-controlled study.

BACKGROUND: Creatine represents a natural supplement and ergogenic aid for sport performance, but there are several concerns regarding its safety for health. The present double-blind placebo-controlled study evaluated the effect of creatine monohydrate supplementation on a panel of blood and urine health indicators in resistance training practitioners. METHODS: Eighteen males performing resistance training three times per week were supplemented with 0.3 g/kg per day creatine monohydrate for 7 days and compared with matched controls supplemented with dextrosol. Blood and urine samples were collected pre- and 30 days post-supplementation to evaluate 41 biochemical parameters and renal function. RESULTS: Creatine monohydrate supplementation did not cause adverse events and, as expected, promoted an increase of the performance and body weight. No modification of red blood cells parameters, white blood cells profile, blood lipid profile, metabolic and urine markers, hepatic and renal function were observed in the supplemented group. CONCLUSIONS: Despite the expected weight increase, the creatine monohydrate supplementation is safe for health and no detrimental effects on different organs and physiological systems were observed in our cohort of volunteers.

Does Creatine Supplementation Affect Renal Function in Patients with Peripheral Artery Disease? A Randomized, Double Blind, Placebo-controlled, Clinical Trial.

BACKGROUND: Case studies and reviews have shown that creatine supplementation can affect kidney function. The objective of this study is to verify the effects of 8 weeks of creatine supplementation on renal function (creatinine clearance: primary outcome) in patients with symptomatic peripheral arterial disease. METHODS: Twenty-nine patients, of both genders, were randomized (1:1) in a double-blind manner for administration of Placebo (PLA; n = 15) or creatine monohydrate (Cr; n = 14). The supplementation protocol consisted of 20 g/day for 1 week divided into 4 equal doses (loading phase), followed by single daily doses of 5 g in the subsequent 7 weeks (maintenance phase). Before and after the supplementation period, markers of renal function, serum creatinine, creatinine excretion rate, and creatinine clearance were evaluated. The Generalized Estimation Equation Model was used for comparison between groups. The level of significance was P < 0.05. RESULTS: No significant differences were found between groups before and after the intervention for serum creatinine (Cr: pre 1.00 ± 0.15 mL/dL vs. post 1.07 ± 0.16 mL/dL; PLA: pre 1.30 ± 0.53 mL/dL vs. post 1.36 ± 0.47 mL/dL, P = 0.590), creatinine excretion rate (Cr: pre 81.73 ± 43.80 mg/dL vs. post 102.92 ± 59.57 mg/dL; PLA: pre 74.37 ± 38.90 mg/dL vs. post 86.22 ± 39.94 mg/dL, P = 0.560), or creatinine clearance (Cr; pre 108 ± 59 mL/min/1.73 m2 vs. post 117 ± 52 mL/min/1.73 m2; PLA: pre 88 ± 49 mL/min/1.73 m2 vs. post 82 ± 47 mL/min/1.73 m2, P = 0.366). CONCLUSIONS: Eight weeks of creatine supplementation is safe and does not compromise the renal function of patients with peripheral arterial disease.

[Effects of creatine supplementation on renal function]. / Efectos en la función renal de la suplementación de creatina con fines deportivos.

Creatine supplements may transitorily rise serum creatinine levels and mimic a kidney disease. If its use is associated with a high protein diet, the resulting increase in blood urea nitrogen will increase the confusion. Since clinical laboratories usually inform the estimated glomerular filtration rate based on serum creatinine, its elevation may lead to over diagnose a chronic renal failure, with the inherent personal and public health consequences. Creatine supplements are safe and do not cause renal disease. Reports of kidney damage associated with its use are scanty. However, creatine supplements should not be used in people with chronic renal disease or using potentially nephrotoxic medications.

Efectos en la función renal de la suplementación de creatina con fines deportivos / Effects of creatine supplementation on renal function

Creatine supplements may transitorily rise serum creatinine levels and mimic a kidney disease. If its use is associated with a high protein diet, the resulting increase in blood urea nitrogen will increase the confusion. Since clinical laboratories usually inform the estimated glomerular filtration rate based on serum creatinine, its elevation may lead to over diagnose a chronic renal failure, with the inherent personal and public health consequences. Creatine supplements are safe and do not cause renal disease. Reports of kidney damage associated with its use are scanty. However, creatine supplements should not be used in people with chronic renal disease or using potentially nephrotoxic medications.

Desempenho de frangos de corte alimentados com inclusão de creatina animal na ração / Performance of broilers fed with inclusion animal creatine in the feed

The objective of this study was to evaluate the productive performance and carcass characteristics of broilers fed with creatine inclusion in the diet. Were evaluated one hundred and sixteen Cobb 500-day-old chicks were divided into four phases: 1 to 7, 8 to 21, 9 to 35 and 22 to 49 days of age, and four experimental diets were formulated, pre-initial, initial, growth and termination, respectively. All diets were produced based on corn and soybean meal. The birds were distributed in a completely randomized design with 0,10% of creatine in substitution to soybean meal and seven replicates. The variables studied were: feed intake (g/bird/day), weight gain (g/bird/day), final weight (g/bird), feed conversion (g/g), viability (%), noble cuts (g), edible offal (g) and carcass yield (%). There was no influence of the inclusion of creatine on the performance parameters of 7 - 21 and 35 days of age. However, there was improvement (P<0,05) in the feed conversion of 7 – 42 days of age. Body weight, carcass weight, thighs, wings, heart, gizzard, liver and carcass yield were not influenced by the inclusion of creatine, except for weight and breast yield for slaughter at 42 days (P<0,05). The inclusion of 0,10% of creatine in diets for broilers provided higher breast weight of birds slaughtered at 42 days and better feed conversion from 7 to 42 days of age.

Objetivou-se avaliar o desempenho produtivo e as características de carcaça de frangos de corte alimentados com inclusão de creatina na ração. Foram avaliados 196 pintainhos de um dia de idade da linhagem Cobb 500, divididos em quatro fases: 1 a 7, de 8 a 21, 22 a 33 e 34 a 49 dias de idade, e formuladas quatro dietas experimentais, pré-inicial, inicial, crescimento e terminação, respectivamente. Todas as dietas foram produzidas a base de milho e farelo de soja. As aves foram distribuídas em delineamento inteiramente casualizado, com 0,10% de creatina em substituição ao farelo de soja e sete repetições. As variáveis estudas foram: consumo de ração (g/ave/dia), ganho de peso (g/ave/dia), peso final (g/ave), conversão alimentar (g/g), viabilidade (%), cortes nobres (g), vísceras comestíveis (g) e rendimento de carcaça (%). Não houve influência da inclusão de creatina sobre os parâmetros de desempenho de 7 – 21 e 35 dias de idade. No entanto, houve melhora (P<0,05) na conversão alimentar de 7 – 42 dias de idade. Peso vivo, peso da carcaça, coxas, asas, coração, moela, fígado e rendimento de carcaças não foram influenciados pela inclusão de creatina, com exceção do peso e rendimento de peito para abate aos 42 dias (P<0,05). A inclusão de 0,10% de creatina em dietas para frangos de corte proporciona maior peso de peito de aves abatidas aos 42 dias e melhor conversão alimentar de 7 a 42 dias de idade.

Desempenho de frangos de corte alimentados com inclusão de creatina animal na ração / Performance of broilers fed with inclusion animal creatine in the feed

The objective of this study was to evaluate the productive performance and carcass characteristics of broilers fed with creatine inclusion in the diet. Were evaluated one hundred and sixteen Cobb 500-day-old chicks were divided into four phases: 1 to 7, 8 to 21, 9 to 35 and 22 to 49 days of age, and four experimental diets were formulated, pre-initial, initial, growth and termination, respectively. All diets were produced based on corn and soybean meal. The birds were distributed in a completely randomized design with 0,10% of creatine in substitution to soybean meal and seven replicates. The variables studied were: feed intake (g/bird/day), weight gain (g/bird/day), final weight (g/bird), feed conversion (g/g), viability (%), noble cuts (g), edible offal (g) and carcass yield (%). There was no influence of the inclusion of creatine on the performance parameters of 7 - 21 and 35 days of age. However, there was improvement (P<0,05) in the feed conversion of 7 42 days of age. Body weight, carcass weight, thighs, wings, heart, gizzard, liver and carcass yield were not influenced by the inclusion of creatine, except for weight and breast yield for slaughter at 42 days (P<0,05). The inclusion of 0,10% of creatine in diets for broilers provided higher breast weight of birds slaughtered at 42 days and better feed conversion from 7 to 42 days of age.(AU)

Objetivou-se avaliar o desempenho produtivo e as características de carcaça de frangos de corte alimentados com inclusão de creatina na ração. Foram avaliados 196 pintainhos de um dia de idade da linhagem Cobb 500, divididos em quatro fases: 1 a 7, de 8 a 21, 22 a 33 e 34 a 49 dias de idade, e formuladas quatro dietas experimentais, pré-inicial, inicial, crescimento e terminação, respectivamente. Todas as dietas foram produzidas a base de milho e farelo de soja. As aves foram distribuídas em delineamento inteiramente casualizado, com 0,10% de creatina em substituição ao farelo de soja e sete repetições. As variáveis estudas foram: consumo de ração (g/ave/dia), ganho de peso (g/ave/dia), peso final (g/ave), conversão alimentar (g/g), viabilidade (%), cortes nobres (g), vísceras comestíveis (g) e rendimento de carcaça (%). Não houve influência da inclusão de creatina sobre os parâmetros de desempenho de 7 21 e 35 dias de idade. No entanto, houve melhora (P<0,05) na conversão alimentar de 7 42 dias de idade. Peso vivo, peso da carcaça, coxas, asas, coração, moela, fígado e rendimento de carcaças não foram influenciados pela inclusão de creatina, com exceção do peso e rendimento de peito para abate aos 42 dias (P<0,05). A inclusão de 0,10% de creatina em dietas para frangos de corte proporciona maior peso de peito de aves abatidas aos 42 dias e melhor conversão alimentar de 7 a 42 dias de idade.(AU)

Creatine supplementation elicits greater muscle hypertrophy in upper than lower limbs and trunk in resistance-trained men.

BACKGROUND: Creatine (Cr) supplementation associated with resistance training produces greater muscular strength improvements in the upper compared with the lower body; however, no study has investigated if such region-specific results are seen with gains in muscle mass. AIM: We aimed to evaluate the effect of Cr supplementation in combination with resistance training on lean soft tissue changes in the upper and lower limbs and trunk in resistance-trained young adult men. METHODS: In a randomized, double-blind and placebo-controlled design, 43 resistance-trained men (22.7 ± 3.0 years, 72.9 ± 8.7 kg, 177.9 ± 5.7 cm, 23.0 ± 2.5 kg/m2) received either creatine (Cr, n = 22) or placebo (PLA, n = 21) over an 8-week study period. The supplementation protocol included a loading phase (7 days, four doses of 0.3 g/kg per day) and a maintenance phase (7 weeks, single dose of 0.03 g/kg per day). During the same period, subjects performed resistance training four times per week using the following two-way split routine: Monday and Thursday = pectoral, shoulders, triceps, and abdomen, Tuesday and Friday = back, biceps, thighs, and calves. Lean soft tissue of the upper limbs (ULLST), lower limbs (LLLST), and trunk (TLST) was assessed by dual-energy X-ray absorptiometry before and after the intervention. RESULTS: Both groups showed significant ( p < 0.001) improvements in ULLST, LLLST, TLST, and the Cr group achieved greater ( p < 0.001) increases in these outcomes compared with PLA. For the Cr group, improvements in ULLST (7.1 ± 2.9%) were higher than those observed in LLLST (3.2 ± 2.1%) and TLST (2.1 ± 2.2%). Otherwise, for PLA group there was no significant difference in the magnitude of segmental muscle hypertrophy (ULLST = 1.6 ± 3.0%; LLLST = 0.7 ± 2.8%; TLST = 0.7 ± 2.8%). CONCLUSION: Our results suggest that Cr supplementation can positively augment muscle hypertrophy in resistance-trained young adult men, particularly in the upper limbs.

Do Health Food Store Staff Steer Teen Boys to Muscle-Enhancing Supplements?

No law prevents their sale to minors.

Effects of long-term low-dose dietary creatine supplementation in older women.

OBJECTIVE: We aimed to investigate the effects of a one-year low-dose creatine supplementation trial on bone health, lean mass, and muscle function in older postmenopausal women. METHODS: A double-blind, randomized, parallel-group, placebo controlled trial was conducted between November 2011 and November 2013 in Sao Paulo, Brazil. Postmenopausal osteopenic women were randomly allocated (1:1) into creatine (n=56; 1g/d) or placebo group (n=53; dextrose at same dose). At baseline and after one year of intervention, we assessed parameters of bone health, body composition, and muscle function. Blood parameters were also assessed before and after the intervention and adverse events were recorded throughout the trial. Possible differences in dietary intake were assessed by three 24-h dietary recalls. RESULTS: Bone mineral density at lumbar spine, femoral neck, total femur, and whole body did not differ within- or between-groups. No significant changes in body weight, BMI, absolute and relative body fat, and body lean mass were observed. Muscle function, as assessed by timed-up-and-go and timed-stands tests, were not significantly changed within- or between-groups. Safety laboratory parameters remained unaltered. CONCLUSION: A one-year low-dose creatine supplementation (1g/d) was free of adverse effects, but did not affect bone health parameters, lean mass, or muscle function in older women. Further studies with longer follow-up periods and higher doses of creatine supplementation are warranted. (Registered at clinicaltrials.gov as NCT01472393).

Creatine supplementation and resistance training in vulnerable older women: a randomized double-blind placebo-controlled clinical trial.

This study aimed to examine the efficacy of creatine supplementation, associated or not with resistance training, in vulnerable older women. A 24-week, double-blind, randomized, placebo-controlled trial was performed. Sixty subjects were assigned to compose the following groups: placebo (PL), creatine supplementation (CR), placebo with resistance training (PL+RT), and creatine supplementation with resistance training (CR+RT). The subjects were assessed at baseline and after 24weeks. The primary outcome was muscle strength, as assessed by one-repetition maximum (1-RM) tests. Secondary outcomes included appendicular lean mass, bone mass, biochemical bone markers, and physical function tests. The changes in 1-RM leg press were significantly greater in the CR+RT group (+19.9%) than in the PL (+2.4%) and the CR groups (+3.7%), but not than in the PL+RT group (+15%) (p=0.002, p=0.002, and p=0.357, respectively). The CR+RT group showed superior gains in 1-RM bench press (+10%) when compared with all the other groups (p≤0.05). The CR+RT group (+1.31%) showed greater appendicular lean mass accrual than the PL (-1.2%), the CR (+0.3%), and the PL+RT groups (-0.2%) (p≤0.05). The CR and the PL+RT groups experienced comparable gains in appendicular lean mass (p=0.62), but superior to those seen in the PL group. Changes in fat mass, bone mass and serum bone markers did not significantly differ between the groups (p>0.05). In conclusion, creatine supplementation combined with resistance training improved appendicular lean mass and muscle function, but not bone mass, in older vulnerable women. Clinicaltrials.gov: NCT01472393.

Creatine supplementation associated or not with strength training upon emotional and cognitive measures in older women: a randomized double-blind study.

PURPOSE: To assess the effects of creatine supplementation, associated or not with strength training, upon emotional and cognitive measures in older woman. METHODS: This is a 24-week, parallel-group, double-blind, randomized, placebo-controlled trial. The individuals were randomly allocated into one of the following groups (n=14 each): 1) placebo, 2) creatine supplementation, 3) placebo associated with strength training or 4) creatine supplementation associated with strength training. According to their allocation, the participants were given creatine (4 x 5 g/d for 5 days followed by 5 g/d) or placebo (dextrose at the same dosage) and were strength trained or not. Cognitive function, assessed by a comprehensive battery of tests involving memory, selective attention, and inhibitory control, and emotional measures, assessed by the Geriatric Depression Scale, were evaluated at baseline, after 12 and 24 weeks of the intervention. Muscle strength and food intake were evaluated at baseline and after 24 weeks. RESULTS: After the 24-week intervention, both training groups (ingesting creatine supplementation and placebo) had significant reductions on the Geriatric Depression Scale scores when compared with the non-trained placebo group (p = 0.001 and p = 0.01, respectively) and the non-trained creatine group (p < 0.001 for both comparison). However, no significant differences were observed between the non-trained placebo and creatine (p = 0.60) groups, or between the trained placebo and creatine groups (p = 0.83). Both trained groups, irrespective of creatine supplementation, had better muscle strength performance than the non-trained groups. Neither strength training nor creatine supplementation altered any parameter of cognitive performance. Food intake remained unchanged. CONCLUSION: Creatine supplementation did not promote any significant change in cognitive function and emotional parameters in apparently healthy older individuals. In addition, strength training per se improved emotional state and muscle strength, but not cognition, with no additive effects of creatine supplementation. TRIAL REGISTRATION: Clinicaltrials.gov NCT01164020.

Effects of creatine supplementation on biomarkers of hepatic and renal function in young trained rats.

Creatine supplementation has been widely used by athletes and young physical exercise practioneers in order of increasing muscle mass and enhancing athletic performance, but their use/overuse may represent a health risk on hepatic and renal impaired function. In this study, we evaluated the effects of 40 days of oral creatine supplementation on hepatic and renal function biomarkers in a young animal model. Wistar rats (5 weeks old) were divided in five groups (n = 7): control (CONTR), oral creatine supplementation (CREAT), moderate exercise training (EXERC), moderate exercise training plus oral creatine supplementation (EXERC + CREAT) and pathological group (positive control for liver and kidney injury) by the administration of rifampicin (RIFAMPICIN). Exercise groups were submitted to 60 min/day of swimming exercise session with a 4% of body weight workload for six weeks. The EXERC + CREAT showed the higher body weight at the end of the training protocol. The CREAT and EXERC + CREAT group showed an increase in hepatic (Aspartate transaminase and gamma-glutamyl transpeptidase) and renal (urea and creatinine) biomarkers levels (p < 0.05). Our study showed that the oral creatine supplementation promoted hepatic and renal function challenge in young rats submitted to moderate exercise training.

Hepatotoxicity associated with dietary energy supplements: use and abuse by young athletes.

 In recent years there has been a significant increase in the consumption of dietary energy supplements (DES) associated with the parallel advertising against obesity and favoring high physical performance. We present the case and outcome of a young patient who developed acute mixed liver injury (hepatocellular and cholestatic) after ingestion of various "over the counter" products to increase muscle mass and physical performance (NO Xplode®, creatine, L-carnitine, and Growth Factor ATN®). The diagnosis was based on the exclusion of other diseases and liver biopsy findings. The dietary supplement and herbal multivitamins industry is one with the highest growth rates in the market, with annual revenues amounting to billions and constantly lacking scientific or reproducible evidence about the efficacy and/or safety of the offered products. Furthermore, and contrary to popular belief, different forms of injury associated with these natural substances have been documented particularly in the liver, supporting the need of a more strict regulation.

Histomorphometric analysis of the effects of creatine on rat myometrium.

OBJECTIVE: To analyze the myometrial thickness of rats subjected to creatine (Cr) ingestion. STUDY DESIGN: A total of 14 rats was equally divided into the control group (ConGr) receiving 1 ml potable water and the creatine group (CrGr) subjected to the ingestion of 1.6 g/kg Cr diluted in 1 ml potable water. At the end of 8 weeks, the animals were anesthetized (xylazine and ketamine) and sacrificed, the uteri and ovaries stained with hematoxylin and eosin, the thickness of both the myometrium and the epithelium measured and the follicles counted. RESULTS: Analysis revealed a significant increase in thickness of the myometrium in the CrGr (272.26 ± 66.71µm) contrasted with that from the ConGr (160.76 ± 35.65µm), CrGr > ConGr (p < 0001). CONCLUSION: Our data suggest that Cr changed myometrial morphology in rats by enhancing myometrial thickness, but its action mechanism in the smooth muscle is still unclear.

Creatine supplementation does not affect clinical health markers in football players.

PURPOSE: To study the effects of 8-week creatine monohydrate (CrM) supplementation on blood and urinary clinical health markers in football players. METHODS: 14 football players were randomly assigned in a double-blinded fashion to Cre (n = 7) or Pla (n = 7) group. The Cre group ingested 15 g/day of CrM for 7 days and 3 g/day for the remaining 49 days, whereas the Pla group ingested maltodextrin following the same protocol. Football-specific training was performed during the study. Total body mass was determined and blood and urine samples were analysed for metabolic, hepatic, renal and muscular function markers, before and after supplementation. RESULTS: A gain of total body mass was observed after CrM intake, but not with placebo. Blood and urinary markers remained within normal reference values. There were no significant changes in renal and hepatic markers after CrM intake. However, total creatine kinase (CK) activity significantly increased, and uric acid level tended to decrease after CrM use. Likewise, serum glucose decreased in the Cre group following supplementation. No significant differences in urine parameters were found in either group after supplementation. CONCLUSIONS: 8 weeks of CrM supplementation had no negative effects on blood and urinary clinical health markers in football players. Properties of CrM may, however, be associated with an increase in CK activity, improving the efficiency for ATP resynthesis, a phenomenon indirectly confirmed by the decreasing tendency in uric acid concentration. Furthermore, CrM seems to slightly influence glucoregulation in trained subjects.

Creatina: auxílio ergogênico com potencial antioxidante? / Creatine: ergogenic aid with antioxidant potential?

A creatina é largamente utilizada como auxilio ergogênico, com algumas evidências quanto ao seu efeito positivo na massa magra, força/potência e resistência muscular. Entretanto, esses estudos não conseguiram identificar potenciais mecanismos bioquímicos que pudessem explicar seu efeito na fadiga ou turnover de proteína muscular, existindo a possibilidade de que alguns indivíduos não sejam responsivos a esse suplemento. Outro possível efeito da creatina, que vem sendo recentemente investigado, é a sua ação antioxidante. Mesmo com poucos trabalhos disponíveis, duas possibilidades existem para explicar esse efeito: 1) Ação indireta como tampão energético, devido ao aumento na concentração tecidual de fosfocreatina, que favoreceria a menor produção de metabólitos do ciclo de degradação de purinas (ciclo de Lowenstein), resultando em queda na formação de hipoxantina, xantina e ácido úrico, assim como em espécies reativas de oxigênio (superóxido, peróxido de hidrogênio e radical hidroxil); 2) Por ação direta, apesar de essa propriedade ser inferior à dos antioxidantes já bem conhecidos, como a glutationa reduzida. Mesmo assim, poderia atuar conjuntamente com estes. O objetivo desta comunicação é relatar dados disponíveis sobre esses dois itens.

Creatine is largely used as an ergogenic aid with some evidence regarding its positive effect on lean body mass, strength/power and muscle endurance. However, most studies were not capable of identifying biochemical mechanisms that could explain its effect on fatigue or muscle protein turnover. There is also the possibility that some individuals are non-responsive to this supplement. Another possible effect of creatine that has been recently investigated is its antioxidant action, but few studies explored this subject. Nonetheless, it can be emphasized that the antioxidant effect of creatine works in the organism in the following way: 1) Indirect action as an energy buffer, due to the increase in muscle phosphocreatine concentrations which would favor a reduced production of metabolites of the purine nucleotide cycle (cycle of Lowenstein) and, as a consequence, a drop in the production of hypoxanthine, xanthine, uric acid, and reactive oxygen species; 2) Direct action (a less powerful action when compared with known antioxidants, such as reduced glutathione). Yet, it could still work in association with them. The objective of this work is to review the available data on the two abovementioned mechanisms.