A college has been fined 400,000 for almost killing two students who participated in a study on caffeine and exercise. Researchers at Northumbria University accidentally administered 30 grams of caffeine to the students instead of 0.3 grams — the equivalent of 300 cups of coffee. After being treated with dialysis, both students were able to make a full recovery, save for some short-term memory loss. That’s surprising — consuming way less caffeine than that could kill a person.
Caffeine is a central nervous system stimulant that has been used by humans to jumpstart their systems for more than 1,000 years. The FDA classifies it as both a drug and a food additive. As the most widely used drug on the planet, caffeine stimulates the brain to increase alertness, raises the amount of acid in your stomach, and gives you a short burst of increased blood pressure. Too much of it, however, can also kill you.
Doctors generally agree that consuming 400 milligrams of caffeine a day is safe for most healthy adults. That’s the equivalent of four cups of brewed coffee and 29,600 fewer milligrams than the students consumed.
The standard four-cup rule isn’t ubiquitous, though; several factors, like height and weight, affect how much you’ll be affected by caffeine. According to the Caffeine Calculator, a safe amount of coffee for a 191-pound man — the average weight of an American male — is 3.2 cups per day. If that 191-pound man had 80 cups of coffee, he will probably die. Comparatively, 66.6 cups of coffee will most likely kill a woman who weighs 159 pounds — the weight of the average American female.
But caffeine overdose is an uncertain science: Jack James, Ph.D., the editor of the Journal for Caffeine Research, told Popular Science that the overdose for adults is about 10 grams of caffeine. However, a 2005 study found that two fatal overdoses occurred after the victims consumed 5 grams of caffeine.
“Caffeine toxicity. . .is not well understood,” James told Popular Science. “There is speculation in the literature regarding the possibility of some individuals having a peculiar sensitivity to caffeine, but there is not clear definition or understanding of what such sensitivity might be.”
And what might caffeine overdose look like, right before a person dies? Symptoms include reactions like a fever, hallucinations, convulsions, and an irregular heartbeat. Regularly overdosing on caffeine can even cause psychosis in otherwise healthy people.