Background: For more than fifty years, low protein diets have been proposed to patients with kidney failure. However, the effects of these diets in preventing severe renal failure and the need for maintenance dialysis have not been resolved.
Objectives: To determine the efficacy of low protein diets in delaying the need to start maintenance dialysis.
Search strategy: Cochrane Renal Group trials register, the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE. Congress abstracts (American Society of Nephrology since 1990, European Dialysis Transplant Association since 1985, International Society of Nephrology since 1987). Direct contacts with investigators. Date of most recent search: December 2004.
Selection criteria: Randomised trials comparing two different levels of protein intake in adult patients suffering from moderate to severe renal failure, followed for at least one year.
Data collection and analysis: Two reviewers independently selected studies and extracted data. Statistical analyses were performed using the random effects model and the results expressed as relative risk (RR) for dichotomous outcomes with 95% confidence intervals (CI). Collection of the number of "renal deaths" defined as the need for starting dialysis, the death of a patient or a kidney transplant during the trial.
Main results: Eight trials were identified from over 40 studies. A total of 1524 patients were analysed, 763 had received reduced protein intake and 761 a higher protein intake. Two hundred and fifty one renal deaths were recorded, 103 in the low protein diet and 148 in the higher protein diet group (RR 0.69, 95% CI 0.56 to 0.86, P = 0.0007). To avoid one renal death, 2 to 56 patients need to be treated with a low protein diet during one year.
Authors' conclusions: Reducing protein intake in patients with chronic kidney disease reduces the occurrence of renal death by 31% as compared with higher or unrestricted protein intake. The optimal level of protein intake cannot be confirmed from these studies.