In college, when I worked part-time as a barista at a local coffee shop, I would often serve the same customers day in and day out. To the point that, before they’d even say anything, I would know what certain people wanted to order: large skim mocha, medium iced latté (light on the milk), black coffee to go, “with room.” Though they took it in different forms, the customers were all ultimately after caffeine.
A study released last Tuesday by an international consortium of caffeine scholars may help explain why some of these customers visited more often than others. Spearheaded by Marilyn Cornelis, a research associate at the Harvard School of Public Health, the team investigated the link between genetics and coffee consumption. By analyzing DNA as well as data on 120,000 adults of European and African-American heritage, the researchers identified eight genetic variants that predispose individuals to seek out and drink caffeine.
“Our results show that people are naturally consuming the amount of coffee that allows them to maintain their optimal level of caffeine” to get that good caffeine feeling without becoming jittery, Cornelis told me. “If we need more, we’re reaching for it.”
Six of the genetic variants examined in the study were newly discovered by the researchers. According to Cornelis, individuals whose DNA expressed all the variants tended to drink around half a cup of coffee more than those without them. Additionally, the new genes can explain about 1.3 percent of all coffee-drinking behavior, or about the same amount that genes can explain other habits, like smoking and alcohol consumption. While those effects may seem small, Cornelis said the study sheds light on why individuals’ bodies and brains react differently to caffeine—and how some people feel anxious after a single cup of coffee, whereas others can down a Starbucks Venti and feel just fine.