Prolonged dietary protein restriction in diabetic nephropathy.

Eleven patients with insulin-dependent diabetes, advancing renal insufficiency, and proteinuria were placed on a diet containing 0.6 g/kg per day of high-biologic-value protein. Selected clinical variables were observed over a 2-year interval. The rate of decline in renal function was significantly decreased during the intervals of protein restriction. The rate during the second 12 months of the study, however, was increased, when compared with the first 12-month interval. Urinary protein excretion decreased significantly, from 2.27 +/- 0.49 g/d to 0.57 +/- 0.40 g/d after the first 12 months of the study, but increased to 1.43 +/- 0.63 g/d after the second 12 months of the study. The dietary protein intake estimated from urea nitrogen excretion in urine samples correlated significantly with urinary protein excretion. These findings suggest that dietary protein restriction has a sustained beneficial effect on the course of diabetic nephropathy, if compliance to the diet can be maintained.