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

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.