On April 26, a South Carolina teen had a heart attack in the middle of class and passed away soon after. A coroner has now announced that his death was caused by drinking a lot of caffeine in a very short time period; Davis Allen Cripe had a McDonald’s latte, a large diet Mountain Dew soda, and an unidentified energy drink in less than two hours.

More specifically, the coroner called it a “caffeine-induced cardiac event causing a probable arrhythmia” (an arrhythmia is loosely defined as abnormal heart beating). Davis did not overdose on caffeine, which is caused by having too much total caffeine in one’s system. If Davis had ingested the same amount over a much longer period of time, he might have been fine.

In other words, both consuming too much caffeine (overdose) and consuming caffeine too quickly (Davis’ tragic case) are dangerous. So, what is the difference between a healthy and unhealthy amount of caffeine?

The Federal Drug Administration has said that about 400 milligrams of caffeine daily is a safe level. The European Food Safety Authority warned that more than 400 milligrams could lead to insomnia (well, duh), panic attacks, and heart problems.

That’s the equivalent of about four cups of coffee on average, but could be a lot more. A normal Starbucks Venti® Hot coffee (one size above large) contains a whopping 340mg, for example. That’s just Starbuck’s featured dark roast; it could be more depending on the brew you choose. Starbucks drinks contain more caffeine than the average coffee chain.

To get a more accurate sense of the amount of caffeine you’re consuming in drinks and food (yep, it’s in food, too, like chocolate), check out the database Caffeine Informer. Be careful of caffeine in a pure, powder form, because just one teaspoon can be lethal; the recommended dose is just 1/16 of a teaspoon.

Above all, beware of energy drinks. Besides containing way more caffeine than most coffee, tea, or soda, they can cause your heart to beat irregularly and increase your blood pressure for hours after you drink them. The latter issue might not even be caused by the caffeine itself: Many of the drinks contain ingredients like guarana and taurine, which haven’t yet been tested on children. Mayo Clinic says that energy drinks may increase risk of heart disease.

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Caffeine Overdose
Beware the Monster drink.

It seems to have been the energy drink that made the difference for Davis. “The chugging of the energy drink at the end was what the issue was with the cardiac arrhythmia,” said the coroner.

“We lost Davis from a totally legal substance,” his father said at a news conference on Monday. “It wasn’t a car crash that took his life. Instead, it was an energy drink. Parents, please talk to your kids about these energy drinks. And teenagers and students: please stop buying them.”

So, long story short: Avoid energy drinks, and don’t drink too many cups of coffee in a day. It’s not a bad idea to monitor how much caffeine you’re consuming to make sure that it’s a healthy level. Avoid caffeine with alcohol, and definitely avoid it with cocaine, a substance which also increases one’s risk of heart attack.

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All of that said, caffeine can also be a great stimulant when ingested safely, and has health benefits, too.

Photos via Getty Images / Tim Boyle, Getty Images / Joe Raedle