Effect of a high-protein diet on kidney function in healthy adults: results from the OmniHeart trial

Abstract

Background: Consumption of a diet high in protein can cause glomerular hyperfiltration, a potentially maladaptive response, which may accelerate the progression of kidney disease.

Study design: An ancillary study of the OmniHeart trial, a randomized 3-period crossover feeding trial testing the effects of partial replacement of carbohydrate with protein on kidney function.

Setting & participants: Healthy adults (N=164) with prehypertension or stage 1 hypertension at a community-based research clinic with a metabolic kitchen.

Intervention: Participants were fed each of 3 diets for 6 weeks. Feeding periods were separated by a 2- to 4-week washout period. Weight was held constant on each diet. The 3 diets emphasized carbohydrate, protein, or unsaturated fat; dietary protein was either 15% (carbohydrate and unsaturated fat diets) or 25% (protein diet) of energy intake.

Outcomes: Fasting serum creatinine, cystatin C, and β2-microglobulin levels, estimated glomerular filtration rate (eGFR).

Measurements: Serum creatinine, cystatin C, and β2-microglobulin collected at the end of each feeding period.

Results: Baseline cystatin C-based eGFR was 92.0±16.3 (SD) mL/min/1.73 m(2). Compared with the carbohydrate and unsaturated fat diets, the protein diet increased cystatin C-based eGFR by ~4 mL/min/1.73 m(2) (P < 0.001). The effects of the protein diet on kidney function were independent of changes in blood pressure. There was no significant difference between the carbohydrate and unsaturated fat diets.

Limitations: Participants did not have kidney disease at baseline.

Conclusions: A healthy diet rich in protein increased eGFR. Whether long-term consumption of a high-protein diet leads to kidney disease is uncertain.

Trial registration: ClinicalTrials.gov NCT00051350.

Figure 1

Between-diet comparisons and 95% confidence intervals (CIs) of (A) estimated glomerular filtration rate (eGFR), (B) cystatin C level, (C) β₂-microglobulin level, and (D) serum creatinine level measured at the end of each feeding period. The 3 feeding periods were the unsaturated fat diet (UNSAT) versus the carbohydrate diet (CARB; triangle), protein diet (PROT) versus the CARB (square), and PROT versus the UNSAT (circle).

Figure 2

Linear fits of the diet-specific change in estimated glomerular filtration rate (eGFR) and change in (A) systolic (SBP) and (B) diastolic blood pressure (DBP). β coefficients resulting from linear regression between change in eGFR and change in SBP were –0.08 (P = 0.4), 0.04 (P = 0.6), and 0.09 (P = 0.2) for the carbohydrate (C), unsaturated fat (U), and protein diets (P), respectively. With regard to DBP, β coefficients were 0.02 (P = 0.9), 0.03 (P = 0.8), and 0.11 (P = 0.4), respectively. Linear fits were truncated at the 5th and 95th percentiles of change in blood pressure.