The Effect of the CYP1A2 −163 C > A Polymorphism on Caffeine Metabolism and Subsequent Cycling Performance

Introduction: Prior studies from our laboratory suggest the −163 C > A polymorphism of the Cytochrome P450 (CYP1A2) gene influences the ergogenic effect of caffeine. However, serum caffeine and/or metabolites have not been reported in these studies. The purpose of this study was to determine whether CYP1A2 polymorphism affects caffeine metabolism and subsequent exercise performance between the genotypes (AA homozygotes and C allele carriers). Material and Methods: Twenty male subjects participated in two 3 km cycling time trials 60 minutes following placebo (all-purpose flour) and caffeine (6 mg/kg BW anhydrous caffeine) supplementation. “Slow metabolizers” were characterized as possessing a C allele (AC heterozygotes and CC homozygotes), and “fast metabolizers” were homozygous for the A allele. Results: C allele carriers had significantly higher serum caffeine after one hour (C allele carriers = 14.2 ± 1.8 ppm, AA homozygotes = 11.7 ± 1.7 ppm, p = 0.001). There were no significant differences (p > 0.05) between genetic groups for any measured caffeine metabolite, the metabolite:caffeine ratio, or the paraxanthine:caffeine ratio. While there was a main effect (p = 0.03) for caffeine ingestion on time trial performance, there was no caffeine x genotype interaction (C allele carriers: placebo = 297.0 ± 20.8 seconds, caffeine = 292.0 ± 20.0 seconds; AA homozygotes: placebo = 318.3 ± 34.5 seconds; caffeine = 307.9 ± 21.9 seconds) (p > 0.05). Conclusions: Results from this study suggest C allele carriers have higher serum caffeine after one hour than AA homozygotes. However, these findings do not support an influence of the CYP1A2 −163 C > A polymorphism on the ergogenic effect of caffeine in a 3 km cycling time trial.