Drinking Four Cups of Coffee Is Probably Safe

“Bring it!”
A Los Angeles news anchor said earlier this month, in response to the announcement that “the world’s strongest coffee” is now available in the United States. The product is called Black Insomnia, a playful nod to a potentially debilitating medical condition that can be caused by the product.
The anchor’s tone took a dramatic decrescendo as she read from the teleprompter: “The site Caffeine Informer says Black Insomnia is one of the ‘most dangerous caffeinated products.’” Her smile faded. “Oh. I’ll have to have this one sparingly.”
Black Insomnia is actually in competition for the title of “world’s strongest coffee.” Another, similar purveyor sells coffee grounds called Death Wish. They come in a black sack with a skull and cross bones. On its Amazon page, Death Wish claims to be “the world’s strongest coffee” and promises its “perfect dark roast will make you the hero of the house or office.”
How much caffeine is required for heroism? At what point does the drug (known technically as 1,3,7-trimethylxanthine) actually become unsafe?
Caffeine occurs in plant leaves and seeds as an insect repellant and herbicide. It is used in hospitals to revive newborns who stop breathing. It can be given intravenously to induce seizures. CNN cautioned against Black Insomnia: “Just one cup could spill you over the daily caffeine limit.”
Multiple news outlets referred to this “limit.” For healthy adults, the number is 400 milligrams per day, and it comes from sources like the Food and Drug Administration and the International Food Information Council. Four hundred milligrams amounts to around four cups of coffee in the old-style sense of the phrase, an eight-ounce mug in a diner. It’s more like one Starbucks venti.
When it comes to caffeine, a drug that’s part of the everyday lives of 90 percent of Americans and a source of great joy—sometimes the actual best part of waking up—that limit can seem less like an admonition than a challenge. Black Insomnia claims to have 702 milligrams of caffeine in a 12-ounce cup. That’s around five times as much as a home-brew, and three times as much as Starbucks’s dark roast. And no serious coffee drinker would stop at 12 ounces. Fill two venti cups with Black Insomnia and you’re at 2,340 milligrams, or about six times the “limit.”