Mediterranean Style Diet and Kidney Function Loss in Kidney Transplant Recipients

Abstract

Background and objectives: Despite improvement of short-term graft survival over recent years, long-term graft survival after kidney transplantation has not improved. Studies in the general population suggest the Mediterranean diet benefits kidney function preservation. We investigated whether adherence to the Mediterranean diet is associated with kidney outcomes in kidney transplant recipients.

Design, setting, participants, & measurements: We included 632 adult kidney transplant recipients with a functioning graft for ≥1 year. Dietary intake was inquired using a 177-item validated food frequency questionnaire. Adherence to the Mediterranean diet was assessed using a nine-point Mediterranean Diet Score. Primary end point of the study was graft failure and secondary end points included kidney function decline (doubling of serum creatinine or graft failure) and graft loss (graft failure or death with a functioning graft). Cox regression analyses were used to prospectively study the associations of the Mediterranean Diet Score with study end points.

Results: During median follow-up of 5.4 (interquartile range, 4.9-6.0) years, 76 participants developed graft failure, 119 developed kidney function decline, and 181 developed graft loss. The Mediterranean Diet Score was inversely associated with all study end points (graft failure: hazard ratio [HR], 0.68; 95% confidence interval [95% CI], 0.50 to 0.91; kidney function decline: HR, 0.68; 95% CI, 0.55 to 0.85; and graft loss: HR, 0.74; 95% CI, 0.63 to 0.88 per two-point increase in Mediterranean Diet Score) independent of potential confounders. We identified 24-hour urinary protein excretion and time since transplantation to be an effect modifier, with stronger inverse associations between the Mediterranean Diet Score and kidney outcomes observed in participants with higher urinary protein excretion and participants transplanted more recently.

Conclusions: Adherence to the Mediterranean diet is associated with better kidney function outcomes in kidney transplant recipients.

Trial registration: ClinicalTrials.gov NCT02811835.

Keywords: Mediterranean diet; adult; chronic graft deterioration; creatinine; death; follow-up studies; graft survival; humans; kidney; kidney transplantation; nutrition; proteinuria; regression analysis; renal insufficiency; renal transplantation; surveys and questionnaires; transplant; transplants.

Copyright © 2020 by the American Society of Nephrology.

Figures

Graphical abstract

Figure 1.

Associations of the Mediterranean Diet Score with graft failure, kidney function decline, and graft loss in stable kidney transplant recipients. Data were fitted by Cox proportional-hazards regression using a Mediterranean Diet Score of 5 as reference value. The black line represents the hazard ratio and the gray area represents the 95% confidence interval.

Figure 2.

Urinary protein excretion and time since transplantation significantly modify the associations between the Mediterranean Diet Score and kidney endpoints. The black line represents the hazard ratio and the gray area represents the 95% confidence interval estimated using Cox regression analyses. The dots refer to the hazard ratios at cut-off values of urinary protein excretion set at 0.5, 1.0, and 3.0 g/d, respectively, and cut-off values of time since transplantation set at 5, 10, and 15 years, respectively.