Background: Since more than fifty years, low protein diets are proposed to patients with kidney failure. However, the effects of these diets in preventing severe renal failure and the need for maintenance dialysis is still controversial.
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 June 1999. Congress abstracts (American Society of Nephrology since 1990, European Dialysis Transplant Association since1985, 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. Exclusion of patients with diabetic nephropathy.
Data collection and analysis: Seven trials selected over 40 studies since 1975. A total of 1494 patients analysed, 753 receiving a reduced protein intake and 741 a larger protein intake. Collection of the number of "renal death" being the need for starting dialysis, the death of a patient or the transplantation of a kidney during the trials.
Main results: 242 renal deaths were recorded, 101 in the low protein diet and 141 in the larger protein diet group, giving an odds ratio of low protein to control of 0.62 with a 95% confidence interval of 0.46 to 0.83 (p<0.001, Peto odds ratio). To spare one extra renal death, 17 patients need to be treated (NNT) with a low protein diet for approximately two years.
Reviewer's conclusions: Reducing protein intake in patients with chronic renal failure do reduce the occurence of renal death by about 40% as compared with larger or unrestricted protein intake and therefore should be warmly recommended to patients. The optimal level of protein intake cannot be deduced from the present work. However, based on other nutritional studies perfomed in patients having chronic renal failure, we recommend a protein intake of 0.6 g/kg/day and an energy intake no less than 35 kcal/kg/day. Skilled dietitian survey should be offered to closely monitor these values and the patient's nutritional status.