Dietary protein intake is not correlated with clinical proteinuria in NIDDM

Objective - To determine whether dietary protein intake is correlated with clinical proteinuria in subjects with non-insulin-dependent diabetes mellitus (NIDDM). Research design and methods - Cross-sectional analysis of data obtained from the San Antonio Heart Study, a population-based survey of diabetes and cardiovascular risk factors. Subjects were enrolled in two phases: phase 1 between 1979 and 1982 and phase 2 between 1984 and 1988. This study was based on 376 NIDDM subjects who had both urinalysis and complete dietary protein intake information available. Dietary protein intake was measured by 24-h dietary recall in phase 1 and by food-frequency questionnaire in phase 2. An early-morning spot urine was obtained from study subjects. Clinical proteinuria was defined as ≥ 1 on Ames Albustix test. Results - In phase 1, the subjects with negative or trace proteinuria had a mean protein intake of 79.9 g/day compared with 72.1 g/day for subjects with ≥ 1 proteinuria. In phase 2, the mean protein intake was 72.2 g/day in the negative/trace group and 65.3 g/day in the ≥ 1 proteinuria group. In multivariate analysis, adjusting for age, sex, ethnicity, systolic blood pressure, and 2-h blood glucose, we were again unable to detect a significant correlation between dietary protein intake and clinical proteinuria. Conclusions - These data do not support the hypothesis that high-protein intake is a risk factor for clinical proteinuria in NIDDM subjects. Therefore, any recommendation for protein restriction in the diets of NIDDM subjects, before the development of NIDDM-related nephropathy, must be made with caution.