EFFECTS OF DIETARY-PROTEIN RESTRICTION ON THE PROGRESSION OF ADVANCEDRENAL-DISEASE IN THE MODIFICATION OF DIET IN RENAL-DISEASE STUDY

Patients with advanced renal disease randomized to the very low-protei n diet group in the Modification of Diet in Renal Disease (MDRD) Study had a marginally (P = 0.066) slower mean glomerular filtration rate ( GFR) decline compared with patients randomized to the low-protein diet group, The objective of these secondary analyses was to determine the relationship between achieved, in addition to prescribed, dietary pro tein intake and the progression of advanced renal disease, A randomize d controlled trial was conducted in patients with chronic renal diseas es of diverse etiology, The average follow-up was 2.2 years, Fifteen u niversity hospital outpatient nephrology practices participated in the study, which comprised 255 patients aged 18 to 70 years with a baseli ne GFR 13 to 24 mL/min/1.73 m(2) who participated in MDRD Study B. Pat ients with diabetes requiring insulin were excluded, The patients were given a low-protein (0.58 g/kg/d) or very low-protein (0.28 g/kg/d) d iet supplemented with keto acids-amino acids (0.28 g/kg/d), Outcomes w ere measured by comparisons of protein intake from food or from food a nd supplement between randomized groups, and correlations of protein i ntake with rate of decline in GFR and time to renal failure or death, Comparison of the randomized groups showed that total protein intake f rom food and supplement was lower (P < 0.001) among patients randomize d to the very low-protein diet (0.66 g/kg/d) compared with protein int ake from food only in patients randomized to the low-protein diet (0.7 3 g/kg/d), In correlational analyses, we combined patients assigned to both diets and controlled for baseline factors associated with a fast er progression of renal disease, A 0.2 g/kg/d lower achieved total pro tein intake (including food and supplement) was associated with a 1.15 mL/min/yr slower mean decline in GFR (P = 0.011), equivalent to 29% o f the mean GFR decline, After adjusting for achieved total protein int ake, no independent effect of prescription of the keto acid-amino acid supplement to slow the GFR decline could be detected, If the GFR decl ine is extrapolated until renal failure, a patient with a 29% reductio n in the rate of GFR decline would experience a 41% prolongation in th e time to renal failure, Additional analyses confirmed a longer time t o renal failure in patients with lower total protein intake. In conclu sion, these secondary analyses of the MDRD Study suggest that a lower protein intake, but not the keto acid-amino acid supplement, retards t he progression of advanced renal disease, In patients with GFR less th an 25 mL/min/1.73 m(2), we suggest a prescribed dietary protein intake of 0.6 g/kg/d. (C) 1996 by the National Kidney Foundation, Inc.