It's happened to all of us at some point or another. The sweaty, jittery, nervous energy that comes when you've over-imbibed. No, I'm not talking about booze. I'm talking about the unpleasant side effects of consuming too much caffeine--the drug that powers early mornings and late nights around the world.
Caffeine is one of the most commonly used drugs in the world--it's in coffee, tea, most sodas, energy drinks, and even chocolate. You may not have known that, like other drugs, it's possible to overdose on caffeine. The jitters, increased urination, shakes, and general anxiety you get from drinking too much coffee are symptoms of the caffeine intoxication, and not to be taken lightly.
No need to fret though, for even the heaviest coffee drinker it's difficult, if not impossible to drink enough coffee to overdose. Most people simply lack the stomach capacity required to overdose on caffeine, at least as long as you're drinking coffee, tea, or soda. However, with an increase in caffeine concentration in certain energy drinks, specifically concentrates like 5-Hour Energy, I wondered if the beverages contained enough caffeine in a small enough volume that abusing them can actually be dangerous.
Lets run the numbers. The median lethal dose for caffeine--that's the amount of caffeine that will kill half of the population that's exposed to it--a 1967 study estimated to be 150mg of caffeine per 1kg of body weight (extract only, unfortunately). That means someone my size, about 100kg (220lbs), would need to consume about 15,000mg of caffeine to reach a dose that kills half of the people who are exposed to it.
I hit the Mayo Clinic caffeine page to see exactly what I'd have to drink to suffer death by over-caffeination. A typical 250mL (about 8oz) cup of coffee contains between 100mg and 200mg of caffeine. Assuming the coffee is on the strong side, I'd have to drink 75 8-oz cups of strong coffee to even come close to the lethal dose. That's 18.75L (5 US gallons) of coffee. No worries there, if I drank 5 gallons of coffee, a caffeine overdose would be the least of my problems.
Sodas aren't likely to cause caffeine overdose either. Mountain Dew has the highest caffeine concentration in commonly available sodas, but it isn't close to coffee: 46mg of caffeine in a 350mL can. No one's going to knock back 326 cans of Mountain Dew fast enough to damage themselves. Even most energy drinks are OK too--Red Bull and Monster have similar caffeine levels about 80mg per 240-250mL container. And let's face it, I can't afford 188 Red Bulls to drink.
After reading too many energy drink labels, it seems like the highest caffeine concentration in a commercially available beverage is 5-Hour Energy. Every 67mL vial of the drink contains just over 200mg of caffeine. To reach 15,000mg of caffeine, I'd need to drink just over 75 5-Hour Energys. It's still 5L of liquid, well over the 1L capacity of most human stomachs.
So the good news is that I probably can't kill myself with caffeine. However, I'm an adult male who weighs 220 pounds. If you weigh half what I do, it will take half the caffeine to get to reach median toxicity. And because the size of the human stomach typically doesn't change much with body weight, drinking 2.5L of 5-Hour Energy is probably possible for someone who weighs 110lbs, although still incredibly unlikely. And, there have been cases of people hospitalized for caffeine overdose after drinking as few as 14 espressos. The good news is that you'll start feeling real crappy well before you keel over dead.
What's the lesson here? Energy drinks probably aren't particularly good for you--just like soda, there's a lot of junk in the can. And like anything else, caffeine is bad for you when it's consumed in massive quantities. So moderation is the key, stop consuming when you start feeling anxious, jittery, or start sweating, and you should definitely follow the instructions on the label--5-Hour Energy explicitly says to drink no more than 2 servings a day, separated by several hours.
Enjoy your highly caffeinated beverages, just enjoy them responsibly.