Protein Intake and Long-term Change in Glomerular Filtration Rate in the Jackson Heart Study

Objective: Dietary protein intake could have deleterious renal effects in populations at risk for chronic kidney disease. Here, we examined whether higher protein intake (≥80th percentile of energy from protein) is associated with decline in kidney function and whether this decline varies by diabetes status.

Design: Observational cohort study.

Subjects And Settings: Participants were African-Americans (n = 5,301), who enrolled in the Jackson Heart Study between 2000 and 2004.

Methods: Dietary intake was assessed using a validated food-frequency questionnaire at baseline, and serum creatinine was measured at baseline (visit 1) and 8 years later (visit 3). Estimated glomerular filtration rates (eGFRs) at baseline and follow-up were computed using the chronic kidney disease epidemiology collaboration equation.

Main Outcome Measure: The change in eGFR was computed by subtracting eGFR at visit 1 from that at visit 3.

Results: Of 3,165 participants with complete data, 64% were women, 57% had hypertension, and 19% had diabetes. The median (25th, 75th percentile) percent energy intake from protein was 14.3 (12.4, 16.4), comparable to that reported for the general US population (15% of energy). During a median (25th, 75th percentile) follow-up of 8.0 (7.4, 8.3) years, eGFR declined by 10.5% from a mean (SD) of 97.4 (17.5) to 86.9 (21.3) mL/min/1.73 m. In the fully adjusted model, consumption of protein as percent of energy intake in lowest and highest quintiles was associated with decline in eGFR among diabetic subjects. The analysis of variance with a robust variance estimator was used to determine whether long-term change in eGFR significantly varies by protein intake.

Conclusions: Our results show that, among African-Americans with diabetes, higher protein intake as a percent of total energy intake is positively associated with greater decline in eGFR in analyses that accounted for risk factors for kidney disease.