At toxic levels — especially when taken in a short time — caffeine can start to cause a number of unpleasant side effects: headache, nausea, vomiting, jitteriness, and irritability.
More severe effects of caffeine toxicity include abdominal pain, seizures, increased blood acid levels, irregular or fast heartbeat, and reduced blood flow to the heart — all of which increase your risk of dying.
Death by caffeine, though, is rare.
One study earlier this year identified 51 caffeine-related deaths.
Another review from this year, published in Food and Chemical Toxicology, found that 14 of 26 caffeine overdose reports resulted in death.
“Many of those [caffeine-related deaths] were associated with exposures on the order or 10 g of caffeine or more, which is quite a bit of caffeine,” study author Daniele Wikoff, PhD, a health sciences practice leader at ToxStrategies Inc., told Healthline.
One person who died ingested 51 g of caffeine.
“In many of these instances,” said Wikoff, “it was consumption of a large amount in a very small amount of time, often from a source like a caffeine pill or the powdered form of caffeine, rather than energy drinks or coffee.”
Even when people didn’t die, they still experienced many of the severe symptoms of caffeine overdose.
“Pounding a bunch of energy drinks in a short period of time,” said Temple, “even if it doesn’t result in death, can certainly result in heart problems or in something that’s going to require an emergency room visit.”
And again, some people seem to be more affected by caffeine than others, even at higher doses. That makes it difficult to predict who will have a bad reaction.
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“The evidence does show that there were some individuals who are sensitive,” said Wikoff, “whether it’s somebody that has a condition that makes them more susceptible, something that interacts differently with the caffeine receptors, or perhaps they metabolize it differently.”
In one case, a person suffered cardiac arrest and died after ingesting only 240 mg of caffeine.
Researchers write that this case is unusual and may be related to preexisting conditions.
But as with the death of Cripe, chugging caffeinated beverages can sometimes have unexpected consequences — even when drinking less than 500 mg of caffeine, as Reuters reported that Cripe did.
“We’re not saying that it was the total amount of caffeine in the system,” Gary Watts, the coroner of Richland County, South Carolina, told Reuters. “It was just the way that it was ingested over that short period of time, and the chugging of the energy drink at the end was what the issue was with the cardiac arrhythmia.”
Energy drinks can also contain other stimulants like guarana, L-carnitine, and taurine that complicate how the body reacts.
So how much caffeine is safe?
The review by Wikoff and her colleagues found that less than 400 mg per day for healthy adults — or less than 2.5 mg per kilogram of body weight per day for healthy teens — is “acceptable.”
The American Academy of Pediatrics recommends that adolescents aged 12 to 18 years should not ingest more than 100 mg of caffeine per day. Younger kids should avoid it altogether.
Recent deaths or toxic reactions to caffeine offer another lesson for parents, teens, and others.
“Just because these products are legal doesn’t mean that overuse of them can’t be harmful,” said Temple.