Creatina x problemas renais

A creatina importante suplemento ergogênico utilizado no esporte com finalidade de melhorar a performance esportiva dos atletas encontra-se atualmente proibida no Brasil, segundo a ANVISA (agência nacional de vigilância sanitária) a proibição é devida ao fato de não existirem estudos de médio e longo prazo mostrando a segurança da creatina. A creatina é uma substância liberada em praticamente todo mundo inclusive nos Estados Unidos onde o FDA imprimide forte controle sobre os suplementos alimentares lá produzidos, e seu uso não é caracterizado como doping nem pelo COI nem pela FIFA, principais orgãos do esporte mundial.

Mas será que não existem realmente estudos mostrando a segurança do consumo da creatina? Abaixo é possível visualizar alguns resumos de estudos realizados afim de chegar a uma conclusão sobre a segurança desse complemento alimentar.

O estudo abaixo analisou o efeito do uso prolongado de creatina em atletas universitários de futebol americano, nos dois grupos de controle não foram encontradas alteração renais nem de outros orgãos vitais:

Effects of long-term creatine supplementation on liver and kidney functions in American college football players.

Mayhew DL, Mayhew JL, Ware JS.

Exercise Science Program, Truman State University, Kirksville, MO 63501, USA.

The purpose of this study was to determine the effect of long-term Cr supplementation on blood parameters reflecting liver and kidney function. Twenty-three members of an NCAA Division II American football team (ages = 19-24 years) with at least 2 years of strength training experience were divided into a Cr monohydrate group (CrM, n = 10) in which they voluntarily and spontaneously ingested creatine, and a control group (n = 13) in which they took no supplements. Individuals in the CrM group averaged regular daily consumption of 5 to 20 g (mean SD = 13.9 5.8 g) for 0.25 to 5.6 years (2.9 1.8 years). Venous blood analysis for serum albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, urea, and creatinine produced no significant differences between groups. Creatinine clearance was estimated from serum creatinine and was not significantly different between groups. Within the CrM group, correlations between all blood parameters and either daily dosage or duration of supplementation were nonsignificant. Therefore, it appears that oral supplementation with CrM has no long-term detrimental effects on kidney or liver functions in highly trained college athletes in the absence of other nutritional supplements.

http://www.ncbi.nlm.nih.gov/pubmed/12500988?dopt=Abstract

Outro estudo analisou os impactos renais da creatina em animais com pré existência de problemas renais e a conclusão do estudo foi que o uso de 4 semanas na concentração de 0,2g por kg corporal não resultou em alterações renais:

Creatine supplementation does not affect kidney function in an animal model with pre-existing renal failure.

Taes YE, Delanghe JR, Wuyts B, van de Voorde J, Lameire NH.

Laboratory of Clinical Chemistry, Department of Internal Medicine, University Hospital Ghent, De Pintelaan 185, B-9000 Ghent, Belgium.

BACKGROUND: Creatine is widely used as an ergogenic substance among athletes. Safety of prolonged creatine intake has been questioned, based upon case reports and animal data. We investigated the effect of prolonged creatine ingestion on renal function in animals with normal kidney function or pre-existing kidney failure, respectively. METHODS: Male Wistar rats were randomly allocated to four experimental groups: (i) sham-operated, control diet; (ii) sham-operated, creatine-supplemented diet (2% w/w (0.9+/-0.2 g creatine/kg body weight/day)); (iii) two-thirds nephrectomized, control diet; and (iv) two-thirds nephrectomized, creatine supplemented diet. Glomerular filtration rate was determined using inulin and creatinine clearance, together with albumin excretion, urea clearance, muscle and serum creatine and serum cystatin C concentrations. RESULTS: In contrast to previous reports, no detrimental effects of creatine supplementation on the renal function indices were observed in two-thirds nephrectomized or sham-operated animals. No differences were observed in inulin (0.28+/-0.08 vs 0.25+/-0.08 ml/min/100 g; P=NS) or creatinine clearance rates. Serum cystatin C concentration, urinary protein excretion, and albumin and urea clearance were comparable between creatine-supplemented and control-diet fed animals in both sham-operated and two-thirds nephrectomized animals. Serum creatine and intramuscular total creatine concentrations were higher in creatine-supplemented groups (P<0.05). CONCLUSIONS:Creatine supplementation at a dosage of 2% w/w for 4 weeks does not impair kidney function in animals with pre-existing renal failure or in control animals.

http://www.ncbi.nlm.nih.gov/pubmed/12543878?dopt=Abstract


Mais estudos devem ser feitos a respeito da segurança da creatina a longo prazo, mas até agora poucos motivos temos para desconfiar da sua segurança, pois os relatos envolvendo "possíveis" danos aos rins causado pela creatina são raros e pouco conclusivos pois outras substâncias conhecidamente danosas como esteróides anabolizantes costumam ser utilizado em conjunto a suplementos alimentares.