The Associations of Plant Protein Intake With All-Cause Mortality in CKD

Abstract

Background: Plant protein intake is associated with lower production of uremic toxins and lower serum phosphorus levels. Therefore, at a given total protein intake, a higher proportion of dietary protein from plant sources might be associated with lower mortality in chronic kidney disease.

Study design: Observational study.

Settings & participants: 14,866 NHANES III participants 20 years or older without missing data for plant and animal protein intake and mortality.

Predictors: Plant protein to total protein ratio and total plant protein intake. Patients were stratified by estimated glomerular filtration rate (eGFR)<60 or ≥60mL/min/1.73m(2).

Outcomes: All-cause mortality.

Measurements: Plant and total protein intakes were estimated from 24-hour dietary recalls. Mortality was ascertained by probabilistic linkage with National Death Index records through December 31, 2000.

Results: Mean values for plant protein intake and plant protein to total protein ratio were 24.6±13.2 (SD) g/d and 33.0% ± 14.0%, respectively. The prevalence of eGFRs<60mL/min/1.73m(2) was 4.9%. There were 2,163 deaths over an average follow-up of 8.4 years. Adjusted for demographics, smoking, alcohol use, comorbid conditions, body mass index, calorie and total protein intake, and physical inactivity, each 33% increase in plant protein to total protein ratio was not associated with mortality (HR, 0.88; 95% CI, 0.74-1.04) in the eGFR≥60mL/min/1.73m(2) subpopulation, but was associated with lower mortality risk (HR, 0.77; 95% CI, 0.61-0.96) in the eGFR<60mL/min/1.73m(2) subpopulation. In sensitivity analyses, results were similar in those with eGFR<60mL/min/1.73m(2) defined by serum cystatin C level.

Limitations: Whether results are related to plant protein itself or to other factors associated with more plant-based diets is difficult to establish.

Conclusions: A diet with a higher proportion of protein from plant sources is associated with lower mortality in those with eGFR<60mL/min/1.73m(2). Future studies are warranted to determine the causal role of plant protein intake in reducing mortality in those with eGFR<60mL/min/1.73m(2).

Keywords: NHANES (National Health and Nutrition Examination Survey); Plant protein; animal protein; chronic kidney disease (CKD); decreased renal function; diet; dietary recall; disease progression; estimated glomerular filtration rate (eGFR); mortality; nutrition; protein intake.

Figure 1

Participant flow chart

Figure 2

Restricted cubic spline of mortality association of plant protein ratio in eGFR ≥ 60 mL/min/1.73 m2 subpopulation

Figure 3

Restricted cubic spline of mortality association of plant protein ratio in eGFR < 60 mL/min/1.73 m2 subpopulation