Elite Athletes Have Mildly Elevated Serum Bilirubin Concentrations

Abstract

Bilirubin is a potent endogenous antioxidant and immune system-modulating substance, which is implicated also in the cell signalization and in various metabolic pathways. Mild elevation of its systemic concentrations seems to provide substantial protection against numerous pathological conditions such as atherosclerotic and inflammatory diseases. Scarce reports in the literature suggest that serum bilirubin might have relevance also to the physical performance. PURPOSE: The aim of the current study was to assess serum bilirubin concentrations in the Czech elite athletes and to compare them with the Czech general population. METHODS: The study was performed in 145 consecutive healthy Czech elite athletes (M:F ratio=1.78) and in 2597 individuals (M:F ratio=0.91) of the Czech post-MONICA study randomly selected from the Czech general population. Serum bilirubin concentrations as well as prevalence of benign hyperbilirubinemia >17 umol/L (1 mg/dL, a phenotypic sign of Gilbert´s syndrome) were evaluated. RESULTS: The medians of serum bilirubin concentrations in the elite athletes were substantially higher compared to the general population (11.75 vs. 9.6 umol/L, p<0.001), and this substantial difference was observed in both men (13.02 vs. 11.3 umol/L, p=0.006) and women (10.29 vs. 8.3 umol/L, p<0.001). Compared to the general population, the prevalence of a phenotypic Gilbert´s syndrome (known also as benign hyperbilirubinemia) was significantly higher in both male (18.4% vs. 31.1%, p=0.004) and female athletes (7.4% vs. 17.3%, p<0.001). CONCLUSIONS: Elite athletes have significantly higher serum concentrations of bilirubin, the most potent endogenous antioxidant substance. Simultaneously, also the prevalence of Gilbert´s syndrome is higher in elite athletes, suggesting that the presence of Gilbert´s syndrome may predispose to better physical performance. This study was supported by grant No. SVV 260156/2019 provided by Charles University.