Once confined to campfires and burnt toast, charcoal is made when wood (or another substance) is burned without complete combustion. Water and volatile organic compounds evaporate, leaving (mostly) carbon behind. Charcoal is an extremely porous substance that’s been known and used for its ability to absorb impurities for generations.

Activated charcoal

Charcoal treated with oxidising gases at high temperatures is called “activated”. Activation creates additional pores, making it more adsorptive. The high temperatures mean it’s very different to the char on meat or burnt toast.

Medical and traditional uses

Activated charcoal is used in hospitals to treat overdoses and some poisonings, and charcoal is also employed in water filtration systems to bind impurities. You can find examples of medicinal charcoal use throughout history, including ancient Greece and Egypt. In the 19th century, charcoal biscuits were sold as a remedy for stomach ailments.

The new black

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It’s easy to see the logic behind charcoal in foods and supplements: if it’s used to treat poisonings, it makes sense it would be healthy. But let’s be real. Adding charcoal to you burger and schnitzel ingredients is a cool gimmick, but it does not turn them into health foods. And while it might be used to treat acute poisonings, in an average healthy person, “daily detoxification” is taken care of just fine by our kidneys and liver.

There is also little evidence that charcoal cures or prevents hangovers (it doesn’t bind alcohol, which is rapidly absorbed from the gut), lowers cholesterol or reduces flatulence.

Possible side effects

If you’re adding it to your smoothies as an excuse to indulge in other bad habits, you’re unlikely to see a net benefit, and it might lull you into a false sense of security. Charcoal can also bind medications (prescription or otherwise), reducing their efficacy. While adsorption varies by chemical properties, charcoal may also bind nutrients (although more investigation is needed before a definitive case can be made). Charcoal can also lead to side effects such as constipation. In short: studies are needed to prove its safety as well as its effectiveness.

The bottom line

Used occasionally or just in the short term, charcoal is probably safe for most adults, but it isn’t likely to have any real health benefit. But, if you are taking any medications, the side effects could outweigh any potential benefits, so it’s best to seek medical advice first.

Dr Emma Beckett is Broadsheet’s nutrition columnist. A molecular nutritionist with a Ph.D. in Food Science, she is a post-doctoral fellow in the School of Medicine and Public Health and the University of Newcastle. In a world of mixed messages she can be found busting nutrition myths and empowering people to critically assess nutrition information. She tweets at @synapse101.