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: Medline and Embase search from January 1966 through to June 1999. Congress abstracts (American Society of Nephrology since 1990, European Dialysis Transplant Association since 1985, International Society of Nephrology since 1987). Direct contacts with investigators.
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. Diabetic nephropathy patients were excluded.
Data collection and analysis: Seven trials were selected from over 40 studies since 1975. A total of 1494 patients were analysed, 753 had received reduced protein intake and 741 a higher protein intake. 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: Two hundred and forty two renal deaths were recorded, 101 in the low protein diet and 141 in the higher protein diet group, giving an odds ratio of 0.62 with a 95% confidence interval of 0.46 to 0.83 (p=0.006). To avoid one renal death, four to 56 patients need to be treated with a low protein diet during one year.
Reviewer's conclusions: Reducing protein intake in patients with chronic renal failure reduces the occurrence of renal death by about 40% as compared with higher or unrestricted protein intake. The optimal level of protein intake cannot be confirmed from these studies.