By one estimate, the average American consumes about 165 milligrams of caffeine per day. For reference, that’s a little more than what you’d get from a small coffee at Dunkin’ Donuts, just over two-thirds of a Starbucks tall, or about three and a half 12-ounce Diet Cokes. Which, to some people, is more than enough to stay bright-eyed and bushy-tailed — but that figure is just an average, which means that a good chunk of the population needs way more than that to make it through the day as a functional human being. Another estimate puts the average closer to 300 milligrams — again, plenty for some, but to the most die-hard coffee drinkers, a paltry amount of fuel.
Good news for those of you who fall into that latter camp: No matter what the average really is, you can pass it without worrying that you’re caffeinating yourself into a permanent jitter. The Food and Drug Administration has previously said that the healthy limit for adults is anything under 400 milligrams of caffeine a day — but according to a review paper recently published in the journal Food and Chemical Toxicology, you can go up to 400 and be just fine.
The authors analyzed more than 700 studies published between 2001 and 2015 that examined the adverse effects of caffeine consumption from “coffee, tea, chocolate, cola-type beverages, energy drinks, supplements, medicines, energy shots, caffeinated chewing gum, caffeinated sport gel, and caffeinated sport bars.” Specifically, they focused their review on acute toxicity, or the poisonous effects of consuming too much caffeine at once, along with longer-term bone, heart, reproductive, and behavioral problems. Their conclusion: 400 milligrams a day (or 300, if you’re pregnant) won’t hurt you.
Granted, that’s a generalization. Some people can handle more caffeine than others, with your personal level of tolerance depending on your genes, your size, and even the medications you’re taking. And as the authors of the review paper noted, research hasn’t really looked in depth at the effects of surpassing 400 — so if you find yourself chugging two Starbucks grandes a day (310 milligrams apiece), it may be time to think about resetting your caffeine tolerance. Good luck.