A number of genes could influence a person’s coffee habit, writes National Geographic. It adds that, together, the CYP1A2 and AHR genes influence the amount of and for how long caffeine circulates in someone’s bloodstream, as CYP1A2 encodes a liver enzyme that metabolizes caffeine and AHR affects how much of that liver enzyme is produced. Someone who quickly metabolizes coffee, Northwestern University’s Marilyn Cornelis tells National Geographic, might be more likely to drink more of it. Meanwhile variants in other genes modulate other effects of caffeine, such as anxiety or an upset stomach, and yet others influence how much caffeine gets by the blood-brain barrier, National Geographic says. And then there are the genes governing taste — some affecting bitter taste receptors could also affect whether or how much coffee a person drinks. But some might drink it anyway. “If you’re very bitter-sensitive … you might still like it either through conditioning or caffeine’s pharmacology effects,” Danielle Reed from the Monell Center adds.