Modification of Diet in Renal Disease

The Modification of Diet in Renal Disease (MDRD) study consisted of two randomized clinical trials that investigated whether protein restriction and control of blood pressure had an effect on the progression of chronic kidney disease (CKD). The study tested two hypotheses—that (1) a reduction in dietary protein and phosphorous intake and (2) the maintenance of blood pressure at a level below that usually recommended safely and effectively delays the progression of CKD.

In study 1, 585 patients with glomerular filtration rates (GFR) of 25-55 ml/min/1.73 m² of body-surface area were randomly assigned to a usual-protein diet or a low-protein diet (1.3 or 0.58 g of protein per kilogram of body weight per day) and to a usual- or a low-blood-pressure group (mean arterial pressure, 107 or 92 mm Hg). In study 2, 255 patients with GFR of 13 to 24 ml/min/1.73 m² were randomly assigned to the low-protein diet (0.58 g per kilogram per day) or a very-low-protein diet (0.28 g per kilogram per day) with a keto acid-amino acid supplement, and a usual- or a low-blood-pressure group (same values as those in study 1). The length of follow-up varied from 18-to-45-months, with monthly evaluations of the patients. The primary outcome was the change in GFR rate over time. The study found that among patients with moderate renal insufficiency, the slower decline in renal function that started four months after the introduction of a low-protein diet suggests a small benefit of this dietary intervention. Among patients with more severe renal insufficiency, a very-low-protein diet, as compared with a low-protein diet, did not significantly slow the progression of renal disease.