Cassava is a popular food and part of the staple diet of half a billion people, but the roots, peel and leaves of the plant are dangerous to eat raw because they contain toxic substances which can produce hydrogen cyanide.

Sweeter versions of cassava can contain as low as 20mg of cyanide per kilogram, but among the bitterest strains that figure can increase to 1,000mg of cyanide.

Cassava is a staple food for 500 million people, but parts of the plant are toxic

The World Health Organisation estimates that cassava poisoning kills about 200 people a year, so while it may be along the ‘world’s deadliest’ foods, the number of people who eat it regularly and are fine is very high indeed.

That’s because human beings are pretty clever, if we’re allowed to pat ourselves on the back a bit here, and have learned how to prepare certain foods that would otherwise pose a health risk to us.

There are chefs who train to prepare an incredibly poisonous fish that would make for a deadly delicacy if not prepared by expert hands and we’ve learned how to lower the risk of being killed by cassava.

Eating parts of cassava raw or not processing them properly can cause death, and has been linked to the neurological disorder ataxia as well, so there are health impacts from this food apart from death.

When prepared properly it’s a staple food for hundreds of millions of people, but it can expose people to hydrogen cyanide if things go wrong

When prepared properly it’s a staple food for hundreds of millions of people, but it can expose people to hydrogen cyanide if things go wrong

Preparing the food properly, which can involve soaking the plant for up to 24 hours, is a key part of making cassava as safe as possible.

The danger posed by cassava seems to increase during times when food is scarce, as during famines and food shortages people may eat more of the bitter cassava which is more likely to contain higher amounts of hydrogen cyanide.

During food shortages in Venezuela in 2017, El Pais reported that people were dying because they were eating the bitter food to stave off starvation.