10.01.2018

People have spent centuries trying to prove caffeine is dangerous, but the science suggests otherwise

When Davis Cripe died in his South Carolina classroom last May, it was a shock to everyone who knew him. He just 16, and healthy. His death made no sense, especially when the coroner said that he’d been killed by a substance most of us consume daily: caffeine.

It’s well-known that caffeine can, in extreme cases, be deadly. About 10 grams of the stuff will kill most people, making caffeine powder an easily accessible (albeit incredibly uncommon and likely painful) choice for suicide. But a typical cup of coffee has less than 100 milligrams—or just 0.1 grams—of caffeine. In other words, you’d need to drink 100 cups of coffee in rapid succession to hit the deadly dose.

For people without underlying medical conditions, it’s exceptionally hard to die from drinking caffeinated beverages because of how (relatively) little caffeine they contain. This is something King Gustav III of Sweden found out in the 18th century, when he conducted an experiment to see whether tea or coffee kills faster. Both test subjects lived well into old age, far outliving King Gustav and the researchers conducting the experiment.

The local coroner said his staff determined Cripe had died from a “caffeine-induced cardiac event causing a probable arrhythmia.” It wasn’t from downing a succession of caffeine pills; it was, the coroner said, because Cripe drank a combination of a large Mountain Dew, some unknown energy drink, and a cafe latte within a few hours.

There’s little scientific evidence suggesting that even high amounts of caffeinated beverages can cause heart arrhythmias. The 2016 studyfound that patients at high risk for arrhythmias could imbibe 500 mg of caffeine in a five-hour span without raising their risk of irregular heartbeat. And a meta-analysis of previous studies found no evidence outside of animal studies, where the animals were given exorbitantly high doses—on the order of 35 mg of caffeine per kilogram of body weight. That would be the equivalent of about 2,550 mg—or 25 cups of coffee—for a 160-pound (73 kg) adult.

Scientists and medical professionals concerned about caffeine generally focus on energy drinks, since they’re wildly popular but contain lots of ingredients that interact in unknown ways, or on combinations of caffeine and alcohol, which get people drunker even as they continue to feel sober. But while energy drinks may be a relatively new concoction, coffee and tea and other traditional caffeinated beverages are not. And there’s extensive research showing it’s wrong to suggest typical caffeine consumption is dangerous.

How caffeine affects the body

When you drink a caffeinated beverage, the chemical immediately dissolves and spreads through all the fluids in your body. The caffeine crosses into the brain within minutes, where it latches onto proteins that normally receive adenosine, a chemical that makes you drowsy.

Caffeine reaches its peak blood concentration between 45 and 60 minutes after you drink it. As time goes on, your liver degrades the caffeine in your blood, meaning there’s less and less to elbow out the adenosine molecules that make you tired. So before too long, you start to get sleepy again. In three to five hours, about half the caffeine from that cup of morning joe will have degraded, so it might feel like time for a refill.

In addition, your brain receptors for adenosine are linked with receptors for dopamine, the “feel-good” chemical. Coffee makes you chipper not just because it’s fighting off drowsiness, but also because it makes it easier for dopamine to do its job, which in turn increases your feelings of pleasure.

But dopamine is also the key ingredient to addiction; drugs like cocaine and amphetamine flood parts of the brain with it to hijack the brain’s reward system—the mental circuitry of motivation. After getting flooded with those feelings of pleasure, you’ll naturally seek those good feelings over and over again. Motivation is important to keeping you alive, like when your brain is making you eat. But it’s not so good when it’s making you snort just one more line at 4am when the bar is trying to close.

Caffeine addiction…or not

If you focus just on dopamine, caffeine looks sort of like really weak cocaine. It’s clear caffeine has reinforcing effects; drinking coffee makes you want to drink more coffee. What isn’t clear is whether it’s truly addictive.

“Caffeine-use disorder” is mentioned in the fifth and latest edition of the Diagnostic and Statistical Manual of Mental Disorders, the professional bible for identifying and categorizing mental health issues. But caffeine-use disorder isn’t a fully recognized diagnosis in the DSM-5; it’s a proposal, currently under consideration for further study.

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