['To compare the effect of a normal protein diet (test diet) in which chicken and fish were substituted for red meat with a low-protein diet (LPD) on glomerular filtration rate (GFR) in normoalbuminuric insulin-dependent-diabetes mellitus (IDDM) patients.', 'A crossover randomized clinical trial was performed in 15 normoalbuminuric IDDM patients, 9 normofiltering, and 6 hyperfiltering patients. They followed three diets for a 3-week period each: a usual diet (UD), an LPD (0.5 g.kg-1.day-1 of proteins, 7% calories as protein, 33% as fat, and 60% as carbohydrates), and a normoproteic isocaloric test diet in which white meat (chicken and fish) was substituted for red meat of the UD. At the end of each diet, a clinical evaluation and measurements of GFR (51Cr-ethylenediaminetetraacetate (EDTA) single injection technique), urinary albumin excretion (UAE), and plasma amino acids were performed. Dietary compliance was assessed by a 24-h urinary urea and weekly interviews with the dietitian.', 'In all diabetic patients, GFR after the LPD (114.9 +/- 16.5 ml.min-1 x 1.73 m-2) and after the test diet (122.7 +/- 16.7 ml.min-1 x 1.73 m-2) was significantly lower than after the UD (132.0 +/- 27.7 ml.min-1 x 1.73 m-2) (P = 0.001). Similar results were found in the hyperfiltering group: after UD = 161.1 +/- 15.4 ml.min-1 x 1.73 m-2, after LPD = 129.8 +/- 9.0 ml.min-1 x 1.73 m-2, and after the test diet = 136.5 +/- 3.1 ml.min-1 x 1.73 m-2, (P < 0.001). In the normofiltering group, no significant changes in GFR were observed after the three diets. Metabolic control, nutritional indexes, blood pressure (BP), and UAE did not change after the three diets in all patients.'] Does chicken and fish diet reduce glomerular hyperfiltration in IDDM patients?