Role of dietary protein and blood pressure in the progression of renal disease.

The Modification of Diet in Renal Disease (MDRD) Study examined the effect of two interventions, reduction of dietary protein and control of blood pressure below the usual recommended level, on the progression of chronic renal disease. Patients in Study A (N = 585), GFR of 25 to 55 ml/min, were randomized to a group following a usual or low protein diet (1.3 or 0.58 g/kg body wt/day) and maintained at a usual (107 mm Hg) or low (92 mm Hg) mean arterial pressure. Patients in Study B (N = 255), GFR 13 to 24 ml/min, were randomized to a group following a low protein diet or a very low protein diet (0.28 g/kg body wt/day supplemented with a mixture of keto acids and amino acids), and maintained at a usual or low blood pressure level. During the first four months of follow-up in Study A, GFR declined at a faster rate in patients assigned a low protein diet or low blood pressure goal. The "terminal" GFR slope (measured from the fourth month of follow-up and projected to 3 years of follow-up) was 28% less, as a mean, in patients in the low protein group versus those on the usual protein diet (P = 0.009). Also, the low blood pressure group showed a significantly (P = 0.006) slower progression of renal disease (29%) than the usual blood pressure group. The effects of low blood pressure on the GFR decline were significantly related to the level of proteinuria during the baseline period. The results of Study B strongly suggest beneficial effects of the very low protein diet on renal function in patients with a GFR less than 25 ml/min.