The Cornelis et al study indicated a positive correlation between increased coffee consumption and the risk of nonfatal myocardial infarction but only in those who were slow metabolizers of caffeine.27 However, when smoking was involved, the results were once again conflicting because smoking induces CYP1A2 activity, and the magnitude of CYP1A2 induction was less pronounced in those who had the variant allele CYPA12*IF. Here, CYP1A2 is linked to myocardial infarction.