There Is Such a Thing as Too Much Coffee, Scientists Say

You drink a lot of coffee, yeah? You roll your eyes at the guy with a “Death Before Decaf” sticker on his MacBook, because you’re more “Death Wish before literally anything.” You know every Starbucks menu hack, and it’s been months before a single barista misspelled your name, because they all know it. (In fact, they all whisper it to themselves either out of habit or out of fear before they fall asleep.) We get it: You drink a lot of coffee.

But Dr. Ang Zhou and Professor Elina Hyppönen from the University of South Australia say that they’ve determined how much coffee is too much coffee, so you might want to put that red eye down for a sec. In their study, which was recently published in The American Journal of Clinical Nutrition, they analyzed UK Biobank data on a whopping 347,077 individuals who ranged in age from 37 to 73, and looked for any associations between their coffee intake and their risk of cardiovascular disease.

"Most people would agree that if you drink a lot of coffee, you might feel jittery, irritable or perhaps even nauseous, Professor Hyppönen said. “That’s because caffeine helps your body work faster and harder, but it is also likely to suggest that you may have reached your limit for the time being. We also know that risk of cardiovascular disease increases with high blood pressure, a known consequence of excess caffeine consumption.”

Their research focused on a gene called CYP1A2 that determines how quickly our bodies can metabolize caffeine. There are two known variants of that gene, the cleverly named ‘slow’ variant and the equally imaginative ‘fast’ variant; according to previous research, those of us who inherited two copies of the ‘fast’ variant can break down caffeine almost four times quicker than someone who has even one copy of the “slow” variant. (So yeah, go ahead and blame your folks if you can’t feel your face after a second shot of espresso.)

ANYWAY, Professor Hyppönen said that even the fastest metabolizers have a limit to how much caffeine they can safely consume—and it’s about half a pot of coffee per day. “In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day,” she explained. “Based on our data, six was the tipping point where caffeine started to negatively affect cardiovascular risk.”

Compared to people who limited themselves to a reasonable-sounding one to two cups a day, the individuals who drank six or more cups had a 22-percent increased risk of developing cardiovascular disease. (Interestingly, people who didn’t drink coffee at all, and those who downed only decaf also had a slightly increased risk—11 percent and 7 percent, respectively—compared to the moderate drinkers).

Science Daily says that this is the first time that any researchers have put an “upper limit” on daily coffee intake, as it relates to heart health. Presumably the study focused on standard cups of coffee, so adjust your Death Wish accordingly.