Boron Intake and decreased risk of mortality in kidney transplant recipients

Abstract

Purpose: In a search for potentially modifiable factors to improve long-term outcome among kidney transplant recipients (KTR), we hypothesized that boron exposure is associated with improved long-term outcome in KTR.

Methods: We determined 24 h urinary boron excretion using inductively coupled plasma mass spectrometry as a measure of boron exposure in 693 stable KTR (57% male, mean age 53y), enrolled in the TransplantLines Food and Nutrition Biobank and Cohort Study. Dietary intake was assessed using validated food-frequency questionnaires.

Results: Linear regression analyses showed that dietary intake of fruit, wine and nuts were key determinants of boron excretion. In addition, boron excretion was negatively correlated with homocysteine and inflammatory parameters. In total, 73 (32%), 47 (20%) and 30 (13%) KTR died among the lowest, middle and highest tertiles of 24 h urinary boron excretion, respectively (P_log-rank < 0.001). Cox regression analyses showed that high boron excretion was strongly associated with lower risk of mortality, independent of age, sex, estimated glomerular filtration rate and history of cardiovascular disease (HR per doubling: 0.51, 95% CI: 0.40 to 0.66, P < 0.001).

Conclusion: Boron may be an overlooked target to improve long-term survival among KTR and potentially other patients, likely through pathways other than inflammation or the methionine-homocysteine cycle that were previously suggested. Interventional trials are warranted to confirm the potential of dietary boron supplementation in KTR and other patient populations.

Keywords: Blue Zones; Inflammation; Mediterranean diet; Trace elements; Transplantation; Wine intake.

Fig. 1

Kaplan–Meier plot for all-cause mortality per tertile of 24 h urinary boron excretion. Tertile 1: < 1040 µg/24 h. Tertile 2: 1040–1540 µg/24 h. Tertile 3: > 1540 µg/24 h. P value represents the evidence against the null hypothesis of no difference in survival across tertiles, as calculated using log-rank test.

Fig. 2

Graphical representation of the association between 24 h urinary boron excretion and risk of all-cause mortality, based on a Cox proportional hazards regression analyses with median boron excretion (1275 µg/24 h) as reference. The model was adjusted for age, sex, eGFR, and history of cardiovascular disease, and presented in relation to the histogram of urinary boron excretion. The black line represents the hazard ratio, the grey area represents the 95% confidence interval. HR hazard ratio