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.
Biology may or may not be destiny, but what’s clear is that recent research has suggested a myriad health benefits to the prosaic (and sometimes romanticized) pastime of drinking coffee. In 2012, the New England Journal of Medicine published a study that showed coffee drinkers may have a lower risk of death. By using data from the National Institutes of Health (NIH)-AARP Diet and Health Study, which involved more than 400,000 participants and 52,000 deaths, the researchers found that those who drank coffee were less likely to report having diabetes, or to perish from “most major causes of death in both men and women, including heart disease, stroke, injuries and accidents, diabetes, and infections.” Overall, people who drank at least two cups of coffee a day had a 12.5 percent lower chance of dying during the 14 years in which the study was conducted than those who didn’t. Still, the same study found that coffee-drinkers were more likely to smoke, and that drinking coffee did not have a significant effect on cancer incidence. Likewise, a study published in 2013 by researchers at the Harvard School of Public Health linked coffee consumption to a 50 percent reduction in suicide risk among both men and women.
"It's unclear how much cognitive decline is diminished by coffee consumption," said Alan Leviton, a neurologist at Harvard Medical School and Boston Children's Hospital. (Leviton consults for the National Coffee Association.) “I can’t tell you what these long-term mental effects are due to; it’s probably much more complex than the current research suggests.”
So what is it about coffee that may protect individuals from such major harms? And if coffee consumption is in part genetically determined, do certain people stand to benefit more from it?
“We need to understand why so many people like and drink coffee, and if we use that understanding to investigate coffee drinking in better detail, we might begin to understand the major illnesses that affect mankind,” said Peter Martin, director of the Vanderbilt Institute for Coffee Studies. “Diabetes, Alzheimer’s, obesity, depression, coronary artery disease—you name it.”
Martin, who has studied caffeine for the past two decades and also serves as director of the Vanderbilt Addiction Center, explains that coffee may even play an important role in combatting alcoholism. Chlorogenic acids—compounds that are naturally present in fruits, tea, and raw green coffee beans—he says, can bind to opioid receptors in the brain, and modify neurotransmitters used by the reward pathways responsible for cravings. Notably, as coffee beans are roasted, their concentration of chlorogenic acids increases; medium roasts tend to have the highest levels of these compounds.
“The key thing that people find difficult to understand is that coffee is more than just caffeine,” Martin told me. “When I started in this field, people were talking about coffee being a guilty pleasure, almost expressing a Puritan ethic of ‘anything that tastes this good can’t be good for you.’ Now people are starting to think coffee may have important biological health benefits.”
So perhaps people who are genetically geared to reach for that extra cup of coffee could be boosting their health, as well as their productivity.