From the way it’s marketed, you’d think activated charcoal was some kind of miracle powder.

It’s best known as a treatment for poisoning, like if a kid accidentally swallowed some cleaning supplies, or for filtering water. But activated charcoal has made its way into all kinds of stuff, like teeth whitening products, cosmetics, and that black ice cream from your Instagram feed last summer.

Now, I hate to break it to you, but it’s probably not the magical health supplement that some people claim it is. Charcoal is a black residue that forms after you burn something with lots of carbon in it, like coal or coconut shells. To make activated charcoal, also known as activated carbon, you treat charcoal with heat and oxygen, or with certain acids and bases.

These chemical reactions can rearrange the carbon atoms to form lots of tiny pores. So activated charcoal has a huge surface area. In fact, just one gram of it can have from 500 to 1500 square meters of surface area.

That’s as much as a globe more than four stories tall! And that lets it trap certain molecules really well, through a process called adsorption. Now, I’m not talking about absorption, where chemicals get trapped inside something, like water soaking into a rag.

Adsorption means molecules bind to the surface of another compound, like the carbon-lined pores in activated charcoal. The molecules bind because of Van der Waals forces, the weak attractive force between uncharged molecules. Basically, depending on where the electrons are, one side of a molecule might be more electrically charged than the other— even if the molecule doesn’t have an overall charge.

So when a molecule passes through the tiny pores in the activated charcoal, those very weak charges make it cling to the carbon thanks to Van der Waals forces. Activated charcoal is good at collecting molecules that contain carbon, like most poisons, because they’re usually large enough and have enough electrons to have stronger Van der Waals interactions. But it can adsorb other molecules, too, like iodine.

And because activated charcoal has such a large surface area, there are plenty of places for poison molecules to bond. Then, the charcoal passes harmlessly through your digestive tract instead of getting sucked into your body, so the poison can’t spread and mess things up. Which is always a plus.

Plenty of studies have been done about it binding poisons in humans or toxins in a water treatment plant, so there’s no doubt that it works for those things. But people have also claimed it can help with hangovers, whiten your teeth, reduce gas in your intestines, and purify mysterious toxins that supposedly build up in your body during normal life. And the evidence there is... less clear.

Some people claim to get whiter teeth from activated charcoal toothpaste, but no one’s done research on it yet. There's also contradictory results about whether it can help with gas by binding to molecules that contain sulfur. And there’s no evidence that it’ll adsorb alcohol or help with hangovers.

So activated charcoal is definitely safe to eat, and might be great for some things... but any miraculous health benefits from eating a black burger bun are probably too good to be true. Thanks for watching this episode of SciShow! And special thanks to Patreon patron Brianna Beecher for asking, and all of our other patrons who voted to have it answered.

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