Activated charcoal has become a lifestyle trend in recent months, with chefs using it to turn everyday foods black and celebrities endorsing its apparent health benefits.
But is the ingredient – often claimed to have detoxing properties – safe to eat?
According to The Daily Mail, sandwich chain Pret A Manger sells a 'charcoal shot' with coconut water, lemon and apple, which it says 'has the flavour of lemonade with a tart kick'.
A restaurant in East London last month caused a stir on Twitter when it unveiled a charcoal croissant, and the ingredient is also found in smoothies.
Activated charcoal is thought to help with digestive problems and bloating, to improve skin and there are even special toothpastes which claim to whiten teeth.
Gwyneth Paltrow, Kim Kardashian and actress Shailene Woodley have all endorsed drinking charcoal lemonade for its supposed cleansing properties.
In the below piece for The Conversation Sophie Medlin, lecturer in nutrition and dietetics at King's College London, explains several reasons to avoid the health fad:
On her Goop website, Gwyneth Paltrow claimed that charcoal lemonade was one of the 'best juice cleansers'.
That was in 2014. Today, charcoal products – from croissants to capsules – are everywhere. Even high street coffee chains have taken to selling charcoal 'shots'.
Some vendors of these products claim that activated charcoal can boost your energy, brighten your skin and reduce wind and bloating.
The main claim, though, is that these products can detoxify your body.
It's easy to see where the claim that activated charcoal can detoxify the body comes from: it is used in emergency medicine to reduce the toxic load when someone has consumed poison or overdosed on medication.
Charcoal binds to poison in the gastrointestinal tract and stops it from being absorbed into the bloodstream.
The toxins are then passed out of the body in the stool.
However, this detoxifying action is another case of the non-scientific nutritionists seeing the medical use for something and misinterpreting its application.