ABSTRACT
Twenty-four patients with idiopathic membranous nephropathy, long-lasting nephrotic syndrome and serum creatinine less than 2 mg/dl ate sequentially, in a randomized cross-over design, a normal protein diet containing 1.1 +/- 0.3 g/kg/day of proteins and a low protein diet containing 0.7 +/- 0.1 g/kg/day of protein, each diet for a period of 3 months. Both diets were low in fat (less than 30% of total calories) and cholesterol (less than 200 mg/day) content and rich in polyunsaturated fatty acids and in linoleic acid (10% of energy). Random assignment to one of the two 3 month diet periods was done after a RUN-IN period of at least one month on the hypolipidic normal protein diet. Glomerular filtration rate (inulin clearance), 24 hour urinary protein loss and serum albumin concentration did not significantly differ at the end of the two diet periods, indicating that long-term restriction of protein intake does not modify GFR or urinary protein loss in nephrotic patients. Serum total and LDL-cholesterol and daily proteinuria were significantly lower at the end of both diet periods than at the beginning and at the end of the RUN-IN period. We suggest that these changes were a consequence of the manipulation of dietary fat intake.
Subject(s)
Dietary Fats/administration & dosage , Dietary Proteins/administration & dosage , Glomerulonephritis, Membranous/diet therapy , Nephrotic Syndrome/diet therapy , Adult , Aged , Cardiovascular Diseases/prevention & control , Female , Glomerulonephritis, Membranous/complications , Glomerulonephritis, Membranous/metabolism , Humans , Lipids/blood , Male , Middle Aged , Nephrotic Syndrome/complications , Nephrotic Syndrome/metabolism , Proteinuria/diet therapy , Proteinuria/etiology , Proteinuria/metabolism , Time FactorsABSTRACT
We studied the effect of dietary protein restriction on glomerular function and proteinuria in nine patients with membranous nephropathy. Patients were randomly assigned to a 3-month period of a normal protein diet (NPD, 1.3 mg/kg/d) or of a low-protein diet (LPD, 0.6 mg/kg/d), in a cross-over design. Dietary protein restriction did not affect glomerular filtration rate (47.8 +/- 10.7 and 49.0 +/- 13.5 mL/min/1.73 m2, LPD and NPD, respectively) and renal plasma flow (456 +/- 119 and 499 +/- 161 mL/min/1.73 m2, LPD and NPD, respectively), nor did it significantly improve glomerular permselective function, as shown by urinary protein excretion (3.1 +/- 2.2 and 3.5 +/- 2.8 g/d, LPD and NPD, respectively) and fractional clearance of albumin, IgG, and neutral dextran molecules of graded molecular size (radii ranging from 2.8 to 6.0 nm). These results indicate that reduction of protein intake to 0.6 g/kg/d does not improve glomerular size selectivity in membranous nephropathy. Thus, in current clinical practice, a protein-restricted diet does not appear to be effective in reducing proteinuria in this category of patients.
