Dietary protein and growth in infants with chronic renal insufficiency: a report from the Southwest Pediatric Nephrology Study Group and the University of California, San Francisco

This report describes growth and nutrition data from the feasibility phase of a clinical trial that was designed to evaluate the effect of diet protein modification in infants with chronic renal insufficiency (CRI). The purpose of the proposed trial was to compare the safety (effect on growth in length) and efficacy [effect on glomerular filtration rate (GFR)] of a diet with a low protein:energy (P:E) ratio versus a control diet in such patients. Twenty-four infants with GFRs less than 55 ml/min per 1.73 m² were randomly assigned at 8 months of age to receive either a low-protein (P:E ratio 5.6%) or control protein (P:E ratio 10.4%) formula, which resulted in average protein intakes of 1.4 and 2.4 g/kg per day in the low and control groups, respectively. Overall energy intakes over a 10-month period of study averaged 92%±12% recommended dietary allowance (RDA) for length in the low-protein group and 92±15% RDA in the control group. Weight for age standard deviation scores (SDS) were comparably low in both groups at the time of randomization (low-protein -2.0±1.3, control -1.9±1.1) and at the end of the study (low -1.9±1.2, control -1.7±0.9). Length for age SDS at entry tended to be lower in the low-protein group but were not significantly different in the two groups (low -2.2±1.4 vs. control -1.7±1.4). However, at 18 months the low-protein group had a significantly lower SDS for length (-2.6±1.2 vs. -1.7±1.4). The length velocity SDS from 12 to 18 months were also different, with the low-protein group remaining strongly negative (-1.0±0.9) while the control group improved (-0.1±1.1). We conclude from this feasibility study that there is a need for caution in advising the use of low-protein intake in infants with CRI. However, our findings should be regarded as preliminary because of the small number of patients and the observation that the weight gains were the same in the two groups.