Low selenium intake is associated with risk of all-cause mortality in kidney transplant recipients.

BACKGROUND: Deficiency of the essential trace element selenium is common in kidney transplant recipients (KTR), potentially hampering antioxidant and anti-inflammatory defense. Whether this impacts the long-term outcomes of KTR remains unknown. We investigated the association of urinary selenium excretion, a biomarker of selenium intake, with all-cause mortality; and its dietary determinants.

METHODS: In this cohort study, outpatient KTR with a functioning graft for longer than one year were recruited (2008-2011). Baseline 24-hours urinary selenium excretion was measured by mass spectrometry. Diet was assessed by a 177-items food frequency questionnaire, and protein intake was calculated by the Maroni equation. Multivariable linear and Cox regression analyses were performed.

RESULTS: In 693 KTR (43% men, 52 ± 12 years), baseline urinary selenium excretion was 18.8 (Interquartile range 15.1-23.4) µg/24-hours. During a median follow-up of eight years, 229 (33%) KTR died. KTR in the first tertile of urinary selenium excretion, compared to those in the third, had over a two-fold risk of all-cause mortality (Hazard ratio 2.36 [95% confidence interval 1.70-3.28], P<0.001), independent of multiple potential confounders including time since transplantation and plasma albumin concentration. The most important dietary determinant of urinary selenium excretion was protein intake (Standardized.β = 0.49, P<0.001).

CONCLUSIONS: Relatively low selenium intake is associated with a higher risk of all-cause mortality in KTR. Dietary protein intake is its most important determinant. Further research is required to evaluate the potential benefit of accounting for selenium intake in the care of KTR, particularly among those with low protein intake.