If you’ve ever wondered why you can’t finish a cup of coffee without starting to shake but your roommate can chug five cups without a problem, coffee science is here with an answer. There’s new evidence that the amount of coffee you drink depends on genetics, and your coffee cravings depend on genes. According to research from a new paper, published in Scientific Reports, the PDSS2 gene, “has been shown to negatively regulate the expression of the caffeine metabolism genes and can thus be linked to coffee consumption.” What that means in layman’s terms is that people in the study with the PDSS2 gene tended to drink less coffee, in part because they crave coffee less.
The gene likely decreases the liver's ability to metabolize caffeine, so those with it need to drink less coffee to get the same buzz. This ability to process caffeine seems to be linked to the amount of coffee that you want—or need, as the case may be—to drink. As the study’s lead author Nicola Pirastu, of the University of Trieste in Italy, explained to Time, “The hypothesis is that people with higher levels of this gene are metabolizing caffeine slower, and that’s why they’re drinking less coffee.” She added, “They need to drink it less often to still have the positive effects of caffeine, like being awake and feeling less tired.”
PDSS2 isn’t the only gene that could have an impact on how you process caffeine, though. Folks with the CYP1A2 gene can process the caffeine in coffee about four times faster than those without the gene. (The researchers of this most recent study contrast the role of CYP1A2 to PDSS2 in their data, so check out the full open-source text if you’d like a deep-dive into that.) And in 2014, researchers at Harvard University found six genetic variants related to coffee consumption and caffeine metabolism.
So if you're having a hard time cutting back on your coffee consumption, just blame genetics.