Serum Bilirubin Concentrations and the Prevalence of Gilbert Syndrome in Elite Athletes

OBJECTIVES: Bilirubin is a potent endogenous antioxidant and immunomodulating substance, which is also implicated in both cell signalling and various metabolic pathways. Mild elevation of systemic bilirubin concentrations provides substantial protection against many diseases of civilization. Rare published reports have suggested that serum bilirubin might also be relevant to sports performance. The purpose of the current study was to evaluate serum bilirubin concentrations and the prevalence of Gilbert syndrome (GS) in elite athletes. METHODS: The study was carried out in 536 consecutive healthy elite athletes and in 2594 individuals of the Czech post-MONICA study representing the general Czech population. Serum bilirubin concentrations, the prevalence of benign hyperbilirubinemia > 17 µmol/L (1 mg/dL, a phenotypic sign of GS), and a variant of the UGT1A1 gene promoter responsible for GS manifestation in Caucasians (rs81753472) were evaluated in study subjects. RESULTS: Compared to the general Czech population, significantly higher serum bilirubin concentrations were found in elite athletes (9.6 vs. 11.6 µmol/L, p < 0.001), both in men (11.3 vs. 12.6 µmol/L, p < 0.001) and women (8.3 vs. 10.5 µmol/L, p < 0.001). Furthermore, the prevalence of GS was also significantly higher in elite athletes (9.6 vs. 22%, p < 0.001) together with the tendency to higher frequencies of the genotypes (TA)(7/7) and (TA)(6/7) UGT1A1. CONCLUSION: Elite athletes have significantly higher concentrations of serum bilirubin, the most potent endogenous antioxidant substance known. Simultaneously, the prevalence of GS syndrome is also much higher in elite athletes, suggesting that a mild elevation of serum bilirubin might predispose to better sports performance. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40798-022-00463-6.