QuickCheck: Is it true that tapioca is poisonous?

TAPIOCA, cassava or as it is locally known, ubi kayu, is a popular tuber here in Malaysia, and traditionally we eat the entire plant.

Fried ubi kayu, masak lemak pucuk ubi and kuih bingka ubi kayu are but a few dishes that we as a nation, love to 'chow' down on.

Many also claim that growing tapioca helped stave off famine during World War 2 as well as during the Emergency. For a humble food item with so much good press, some say it actually has a dark side.

Is it true that tapioca, aka ubi kayu, is actually poisonous?



Yes, raw ubi kayu is a poisonous plant and depending on which type you are talking about, the scale goes from rather poisonous to extremely "call your undertaker" poisonous.

And it's not just the tuber that's the problem, it's the entire plant, leaves, stems and all.

Broadly speaking, there are two types of tapioca, sweet and bitter, with the bitter one being roughly eight times more toxic.

Tapioca is full of cyanogenic glycosides, which by themselves are not inherently toxic but react to enzymes in your saliva to release hydrogen cyanide, a chemical that is highly toxic to people.

In fact, hydrogen cyanide was used by the French as a chemical weapon during World War 1.

Symptoms of cyanide poisoning caused by improperly prepared tapioca include a drop in blood pressure, rapid pulse and respiration, headache, dizziness, pain, vomiting, diarrhea, confusion and even convulsions.

And it doesn't take much for the symptoms to start as a lethal dose ranges between 0.5mg to 3.5mg per kilogramme (kg) of body weight.

This means children, being smaller, are more susceptible to poisoning.

For reference, sweet cassava has about 50mg per kg of tuber, whereas the bitter type has 400mg.

The silver lining to this gastronomical doom and gloom is the fact that sweet tapioca (the one we commonly eat here) is relatively easy to process, all you have to do is to cook it thoroughly in order to break down the cyanogenic glycosides.

Making bitter cassava takes more doing as you have to soak it in water for long periods of time to leach out as much of the toxins as possible before thoroughly cooking it.

Though not common here, mass poisonings involving tapioca do occur in countries.

A significant one involved the deaths of 27 school children and hospitalised 100 more in the Philippines back in 2005.

Bottom line is, tapioca is a wonderful food item that is very nutritious, filling and easy to grow. Just try to stay away from any ubi kayu salads and you should do fine.


1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5113521/

2. https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_19_01.html

3. http://www.todayifoundout.com/index.php/2014/11/tapioca-cyanide/

4. https://www.medicalnewstoday.com/articles/323756

5. https://www.thestar.com.my/news/regional/2005/03/11/parents-bury-victims-who-died-of-poisoning

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