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While you unwrap that luscious truffle, let Hank explain the science of chocolate -- where it comes from, what its active ingredient is, and how it works. Also learn the difference between chocolate, cocoa, cacao and coca, so you really know what you're talking about the next time you pas the candy disk.


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Hank Green: If you are human, and you have a tongue, you have no doubt eaten and enjoyed and possibly become obsessed with chocolate.  Some people can't get enough of it, others claim it has aphrodisiac properties, and yet this delicious confection can kill your dog without mercy.  So, before you unwrap that truffle, why not get the facts about humanity's favorite sweet?

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Hank: First, let's get our terms straight.  What's the difference between chocolate, cocoa, and the ingredient you see on a lot of chocolate wrappers these days, cacao?  They are all products of the same plant, native to Central and South America, Theobroma cacao.  Since at least the heyday of the Olmec culture in Mexico 3000 years ago, and to much of the rest of the world since then, the fruit of that plant is and has always been known as cacao.

But it seems that English speakers long ago swapped around some of the vowels and started calling it cocoa, because that's just how we do.  And for a very long time, both words referred to the same specific thing: the powder made from the dried fermented fruit of the cacao tree.  These days though, foodies will tell you that the terms can describe cacao extract that's processed in slightly different ways, stuff labeled as cacao generally has had the fat in the fruit, known as cocoa butter, removed by pressing it cold, whereas cocoa is usually heated to get the fat out.

Chocolate, meanwhile, is just food made from this cacao, or cocoa, but with a whole bunch of sugar and milk fat added to it.  By the way, there's also coca, which has nothing to do with cacao or chocolate; coca is a product of the coke plant, also from South America, whose leaves yield a mild stimulant when chewed or drunk as tea.  So trust me, Milky Ways, Zagnuts, the things you get in Halloween candies, no cocaine.

The confusion between these two plants may stem from the fact that cacao is its own kind of natural stimulant.  While some studies have suggested that cacao contains chemicals that can imitate our feel-good neurotransmitters, its main active ingredient is theobromine, which is very similar to caffeine.  It's also found in tea and cola nuts.  But instead of giving you that hyper 'Let's have a push up contest" kind of rush, it creates more alertness or sharpness of mind, the kind that comes in handy when you're, you know, aligning giant stone monuments with the equinoxes or something.

But theobromine also functions as a vasodilator, a chemical that causes blood vessels to relax and blood to move more freely.  This can not only help arouse the brain and ease the heart, it also can have a distinctly Viagra-like effect on some men, which may be the origin of chocolate's reputation as an aphrodisiac.

But as with all stimulants, theobromine has its downsides.  It can be a powerful diuretic, and even though it's not nearly as strong as caffeine, large amounts can cause effects similar to those of a caffeine overdose, like anxiety, headaches, and nausea.  In fact, some Meso-American cultures used cacao to make a kind of ceremonial brew to induce vomiting.  And many Mississippian cultures in the South used cacao's cousin, a holly called Ilex vomitoria to mix up a similar drink for ritual barfing.  

Speaking of barfing, it is true that chocolate is highly toxic to dogs, not because it's poisonous in itself, but because it takes dogs much longer to metabolize theobromine.  While we might feel chocolate's buzz for a half an hour or so, it can linger and accumulate in a dog's system for a day or even more, causing an overdose, with vomiting, diarrhea, even seizures and possible organ failure.

The problem is actually worse for cats, but they rarely get poisoned because they can't taste sweetness, so they aren't all that into chocolate.  Poor kitties, they can't taste sweetness.  But it's good, though, that they're not dying.  Good and bad.  It's a balance.  And while there's some anecdotal evidence of people becoming addicted to chocolate, it's hard to isolate the true source of the craving, whether it's the theobromine or the fat and sugar and other stuff that have been found to fuel a broader food addiction.  Me, I'm just gonna stick to my Milano cookies, just one or two a day.  This had a peppermint in it.  

Thank you for watching this tasty SciShow Dose, and thanks especially to all of our subscribers on Subbable, who continue to make this show possible, and now, you can celebrate your love of both SciShow and chocolate with an official SciShow chocolate bar.  Ooh, it's even printed with SciShow on the thing.  To find out how, go to and as always, you can find us on Facebook and Twitter, too, don't forget to go to and subscribe.

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