THE EFFECT OF DIETARY-PROTEIN RESTRICTION ON THE PROGRESSION OF DIABETIC AND NONDIABETIC RENAL DISEASES - A METAANALYSIS

Background: Dietary protein has long been thought to play a role in th e progression of chronic renal disease, but clinical trials to date ha ve not consistently shown that dietary protein restriction is benefici al. Purpose: To use meta-analysis to assess the efficacy of dietary pr otein restriction in previously published studies of diabetic and nond iabetic renal diseases, including the recently completed Modification of Diet in Renal Disease Study. Data Sources: The English-language med ical literature published from January 1966 through December 1994 was searched for studies examining the effect of low-protein diets in huma ns with chronic renal disease. A total of 1413 patients in five studie s of nondiabetic renal disease (mean length of follow-up, 18 to 36 mon ths) and 108 patients in five studies of type I diabetes mellitus (mea n length of follow-up, 9 to 35 months) were included. Study Selection: Randomized, controlled studies were selected for nondiabetic renal di sease; randomized, controlled studies or time-controlled stud ies with non randomized crossover design were selected for diabetic nephropath y. Data Extraction: Data in tables, figures, or text were independentl y extracted by two of the authors. Data Synthesis: The relative risk f or progression of renal disease in patients receiving a low-protein di et compared with patients receiving a usual-protein diet was calculate d by using a random-effects model. In five studies of nondiabetic rena l disease, a low-protein diet significantly reduced the risk for renal failure or death (relative risk, 0.67 [95% CI, 0.50 to 0.89]). In fiv e studies of insulin-dependent diabetes mellitus, a low-protein diet s ignificantly slowed the increase in urinary albumin level or the decli ne in glomerular filtration rate or creatinine clearance (relative ris k, 0.56 [CI, 0.40 to 0.77]). Tests for heterogeneity showed no signifi cant differences in relative risk among studies of either diabetic or nondiabetic renal disease. No significant differences were seen betwee n diet groups in pooled mean arterial blood pressure (diabetic and non diabetic patients) or glycosylated hemoglobin level (diabetic patients only). Conclusion: Dietary protein restriction effectively slows the progression of both diabetic and nondiabetic renal diseases.