The purpose of the investigators study was to determine the effect of dietary protein restriction on survival and progression to end stage renal disease (ESRD) in diabetic nephropathy.

The study was a prospective, randomized, unmasked, controlled trial carried out at the Steno Diabetes Center. With concealed randomization the patients were (in blocks of two according to the level of GFR) assigned to receive either a usual-protein diet or a low-protein diet.

After randomization an iso-caloric low-protein diet of 0.6 g/kg/day was prescribed to patients in the low-protein diet group. The usual-pro tein diet consisted of the patients' pre-study diet.

The planned duration of follow-up was four years, scheduled visits every three-months. All patients gave complete history of medication, underwent examination of weight, urinary albumin-, sodium- and urea excretion, serum albumin, serum urea, hemoglobin, hemoglobin A1c, blood pressure, serum total-cholesterol, high-density lipoprotein (HDL) cholesterol.

GFR, serum triglycerides,calcium and phosphorous, anthropometric measurements, nutritional status and smoking habits were evaluated every six months.

Dietary protein intake was estimated on the basis of three consecutive 24-hour urine samples completed before each visit, using urinary excretion of urea nitrogen.

GFR was measured by plasma clearance of 51Cr-EDTA over a 4 hour period and standardized for 1.73m2 body surface area using the same surface for each patient during the study.

Inclusion Criteria:

• Diabetes mellitus type 1
• duration at least 10 years
• onset before age of 35,
• presence of diabetic retinopathy
• albuminuria>=300mg/24 h in at least 2/3 sterile urine samples
• no clinical or laboratory evidence of other kidney or urinary tract disease
• GFR above 20mL/min/1.73M2
• pre-study decline in GFR>= 2 mL/min/year

Exclusion Criteria:

• pregnancy
• history of congestive heart failure or myocardial infarction or coronary bypass surgery within the last three months