Background: Some studies have suggested that a low-protein diet slows the deterioration of renal function in patients with chronic renal failure (CRF). The effects of a low-protein diet on renal function and growth, have not been assessed in a large, prospective randomised trial in children with CRF.
Methods: A 2-year prospective, stratified, and randomised multicentre study recruited 191 patients aged 2-18 years. After a run-in period of at least 6 months, patients were stratified into either a progressive or non-progressive category based on the change in creatinine clearance in this period. The patients were also stratified into three renal-disease categories and then randomly assigned to a control or diet group. In the diet group, the protein intake was the lowest, safe WHO recommendation--i.e., 0.8-1.1 g/kg daily adjusted for age. All patients were advised to have a calorie intake of at least 70% of the WHO recommendations. Glomerular filtration rate (GFR) was measured every 2 months by creatinine clearance; dietary compliance was checked by urinary urea-nitrogen excretion and dietary diaries (weighing method). 112 patients completed an optional third year of the study.
Findings: The low-protein diet did not affect growth. However, there was no effect of diet on the mean decline in creatinine clearance over 2 years (diet vs control: progressive group -9.7 [SD 8.0] vs -10.7 [11.8] mL/min per 1.73 m2; non-progressive group -2.5 [7.5] vs -4.3 [10.0] mL/min per 1.73 m2). Patients classified as having progressive disease were older and had a lower creatinine clearance and a higher blood pressure at randomisation, and had a greater decrease in creatinine clearance than non-progressive patients. On multivariate regression analysis proteinuria (partial R2 = 0.259) and systolic blood pressure (partial R2 = 0.087) were independent predictors of the change in GFR. Similar results were found after the study was extended for a third year.
Interpretation: A low-protein diet for 3 years did not affect the decrease in renal function in children with CRF. Proteinuria and blood pressure explain a large part of the variability of, and may be causally related to the decline in the GFR.