Diabetic nephropathy: is dietary protein harmful?

The suggested harmful effect of dietary protein on renal function in diabetic nephropathy was tested in three groups of insulin-dependent diabetic patients: 1) 10 patients without signs of nephropathy in spite of at least 30 years of diabetes; 2) 11 patients with nephropathy and reduced but stable glomerular filtration rate (GFR) (decline less than 4 ml/min per year [mean 1.8] during the last 2 years); 3) 10 patients with progressive nephropathy with GFR declining by an average of 11 ml/min per year. Dietary protein intake was estimated from a dietary history interview, as well as from urinary excretion of nitrogen (mean = 4.7 samples). Both methods showed a wide range of protein intake in all three groups of patients (0.6-2.3 g/kg body weight [BW]). The mean values did not differ between the groups, 1.30, 1.34, and 1.24 g/kg BW by interview, and 1.20, 1.10, and 1.13 g based on urinary nitrogen levels. There was no correlation between rate of decline of GFR and protein intake, even in those patients with no or minimal decline. These results do not support the hypothesis that dietary protein is a factor of importance in the development or progression of human diabetic nephropathy.

Nitrogen balance studies in patients with uremia during treatment with protein-reduced diet and supplementation with essential amino acids or keto acids.

Nitrogen balance was studied in 4 patients with uremia during treatment with a protein-reduced diet (20 g) supplemented with either essential amino acids and histidine or a mixture of keto analogues of five of the essential amino acids and essential amino acids. 3 patients completed the study. Nitrogen balance was negative on the diet only and was improved with both forms of supplementation. However, supplementation with the keto acids did not offer any advantage over the conventional essential amino acid supplementation. 1 patient developed serious hypercalcemia during treatment with the keto acid supplementation.

Protein-reduced diet in diabetic renal failure.

The effect of treatment with a protein-reduced diet (20-30 g/day) and essential amino acids was studied in 21 patients with diabetes mellitus and renal failure. The mean treatment time was 5.0 (0.5-14) months. Most patients experienced considerable amelioration of their uremic symptoms and the mean serum value was reduced by 50% of the initial value during treatment. Residual renal function continued to decrease during treatment. Vigorous treatment of fluid retention and hypertension was a prerequisite for a successful course and may also have decreased the rate of progression towards dialysis. Compliance with the diet was not different from that found in non-diabetic uremic patients. Satisfactory control of blood glucose levels was obtained with no or only minor adjustments of the insulin dosage. It is concluded that dietary therapy should be considered in diabetic patients with renal failure for treatment of uremic symptoms.