Is cassava poisonous?
The claim: Cassava is poisonous.
Last checked 2 November 2026
Raw, yes. Cassava roots carry compounds that release cyanide, and even sweet cassava, at the levels FSANZ gives as typical, holds more than Europe's one-sitting safety limit for an adult in a cupful when raw. The international food standard's rule is: peel it and cook it through. Cooking removes much of the cyanide but not all of it, and flour from high-cyanide wild cassava has killed people.
The table below works out how much raw root, cooked root and flour reaches Europe's safety limit for one sitting and the low end of the lethal range, for your body weight.
Where the cyanide is
Cassava's cyanide comes from cyanogenic glycosides: compounds that release hydrogen cyanide when the root's cells are broken. How much a root carries depends on the variety. Australia and New Zealand's food standards agency, FSANZ, gives the ranges:
Sweet varieties of cassava will typically contain approximately 15 to 50 mg/kg of hydrogen cyanide on fresh weight basis.
Values from 15 to 400 mg/kg of hydrocyanic acid in cassava roots on a fresh weight basis have been mentioned in the literature.
The international food standard draws the line between sweet and bitter cassava at the same point, and adds a rule for both:
Sweet varieties of cassava are those that contain less than 50 mg/kg hydrogen cyanide (fresh weight basis).
In any case, cassava must be peeled and fully cooked before being consumed.
The EU sets the same ceiling for fresh peeled cassava root, and a lower one for cassava and tapioca flour; the table includes both.
What cooking does
FSANZ bought raw frozen cassava in shops, tested it, then cooked it and tested it again:
One raw sample had a maximum total HCN concentration of 81 mg HCN/kg
all cooking methods resulted in a marked reduction in the HCN content of cassava roots, with a mean reduction of 56% (range of 28-83%).
The HCN concentration of the non-compliant sample decreased from 81 mg HCN/kg to 37 mg HCN/kg after cooking.
Unfortunately, the sample numbers were too small to determine if there is any statistically significant difference between the HCN reductions that occurred by different cooking methods.
So cooking helps a lot, but it does not take the cyanide to zero. FSANZ worked out what that means for a large serving of cooked cassava, measured against its own safety limit, which is set higher than EFSA's (see the next section):
the ARfD of 80 µg HCN/kg bw established by FSANZ
Table 14 indicates that cooked cassava with concentrations of total HCN approaching 30 mg HCN/kg leads to acute dietary exposure estimates that exceed the ARfD.
HCN is hydrogen cyanide; ARfD is the acute reference dose, the safety limit for one sitting.
Two different lines: the safety limit and the lethal dose
As on our almonds and apple seeds pages, two lines matter: EFSA's safety limit for cyanide in one sitting, and the dose reported to kill.
An acute reference dose (ARfD) of 20 μg/kg bw was derived from an exposure of 0.105 mg/kg bw
The acute lethal oral dose of cyanide in humans is reported to be between 0.5 and 3.5 mg/kg body weight (bw).
bw means body weight.
How much cassava, for your body weight
The table works out how much of each reaches the two lines. Raw rows also give cups, using USDA's cup of raw cassava.
| Cassava | Cyanide per kg | Reaches EFSA's safety limit | Reaches the low end of the lethal range |
|---|---|---|---|
| Sweet cassava root, raw (FSANZ Technical Report 28 (2004)) | 14.4–48.1 | 29.1–97 g (less than a quarter cup – 0.471 cup) | 727–2,420 g (3.53–11.8 cups) |
| Raw frozen cassava bought in shops (highest of nine samples) (FSANZ, 2014) | 78 | 18 g (less than a quarter cup) | 449 g (2.18 cups) |
| The same sample after cooking (FSANZ, 2014) | 35.6 | 39.3 g | 983 g |
| Cassava roots, raw, all varieties including bitter (reported range) (FSANZ Technical Report 28 (2004)) | 14.4–385 | 3.64–97 g (less than a quarter cup – 0.471 cup) | 90.9–2,420 g (0.441–11.8 cups) |
| Cassava or tapioca flour at the EU legal maximum (EU Regulation 2023/915) | 9.63 | 145 g | 3,640 g |
| Cassava flour behind the 2017 Uganda outbreak (CDC MMWR, 2019) | 85–90 | 15.6–16.5 g | 389–412 g |
The raw rows assume nothing is lost; real cooking takes much of it away, as the cooked row shows. Children are smaller, so the same amount gives them a bigger dose for their weight: try a child's weight.
When processing goes wrong
In Uganda in 2017, a batch of cassava flour caused an outbreak of suspected cyanide poisoning. The US Centers for Disease Control and Prevention reported:
In September 2017, an outbreak of suspected cyanide poisoning, involving 98 cases with two deaths, occurred in western Uganda.
contained cyanogenic glycoside that was equivalent to an average of 88 ppm of cyanide (range = 85–90), more than eight times the recommended safe level of 10 ppm
Epidemiologic and laboratory investigation identified consumption of a cassava flour dish made from wild cultivars of cassava with high cyanogenic content as the cause of the outbreak.
The table includes that flour beside flour at the EU legal maximum.
What you'll hear at the table
Here is each cassava claim, checked against its source.
You'll hear: Cassava is poisonous raw.
Holds up
Cassava roots carry cyanide-releasing compounds, and even sweet cassava holds more than EFSA's one-sitting limit for an adult in a cupful when raw (see the table).
In any case, cassava must be peeled and fully cooked before being consumed.
You'll hear: Cooking makes cassava safe.
Partly holds up
Cooking removes much of the cyanide, but how much varies, and a large serving of cooked cassava can still pass the safety limit.
all cooking methods resulted in a marked reduction in the HCN content of cassava roots, with a mean reduction of 56% (range of 28-83%).
You'll hear: Cassava flour and tapioca are poisonous.
Partly holds up
Flour at the EU limit takes more grams to reach the safety limit than any root row in the table. Flour made from high-cyanide wild cassava is another matter: it caused the Uganda outbreak.
contained cyanogenic glycoside that was equivalent to an average of 88 ppm of cyanide (range = 85–90), more than eight times the recommended safe level of 10 ppm
You'll hear: Cassava can kill you.
Holds up
It has. The Uganda outbreak was traced to flour from high-cyanide wild cassava.
In September 2017, an outbreak of suspected cyanide poisoning, involving 98 cases with two deaths, occurred in western Uganda.
The referee's verdict
- Right, for the "plants fight back" side: cassava roots carry cyanide-releasing compounds, raw sweet cassava passes Europe's safety limit in less than half a cup, and flour from high-cyanide wild cassava has killed people.
- Right, for the cassava eater: peeled and cooked through, cassava loses much of its cyanide, and flour at the EU limit takes more grams to reach the safety limit than any root row in the table.
- Not settled: exactly how much a given way of cooking removes; FSANZ found a wide range, and its samples were too few to compare methods.
Try it with your own plate
See what cassava gives you, and what comes with it.
Sources
- Food Standards Australia New Zealand. Cyanogenic glycosides in cassava and bamboo shoots: a human health risk assessment. Technical Report Series No. 28, July 2004. (opens in a new tab)Evidence: Regulatory assessmentRead: PDF text layer, in Chrome
- Food Standards Australia New Zealand. Survey of cyanogenic glycosides in plant-based foods in Australia and New Zealand 2010–13. (opens in a new tab)Evidence: Measured in foodRead: PDF text layer, in Chrome
- Codex Alimentarius. Standard for Sweet Cassava (CXS 238-2003). (opens in a new tab)Evidence: Regulatory assessmentRead: PDF text layer, in Chrome
- Commission Regulation (EU) 2023/915 on maximum levels for certain contaminants in food, Annex I, section 2.3. (opens in a new tab)Evidence: Regulatory assessmentRead: page text, in Chrome
- Outbreak of Cyanide Poisoning Caused by Consumption of Cassava Flour — Kasese District, Uganda, September 2017. Morbidity and Mortality Weekly Report 68(13). (opens in a new tab)Evidence: Case reportRead: page text, in Chrome
- EFSA Panel on Contaminants in the Food Chain (CONTAM) (2016). Acute health risks related to the presence of cyanogenic glycosides in raw apricot kernels and products derived from raw apricot kernels. EFSA Journal 14(4):4424. (opens in a new tab)Evidence: Regulatory assessmentRead: Wiley full text, in Chrome (16 Oct 2026, for the apple seeds page)
- EFSA Panel on Contaminants in the Food Chain (CONTAM) (2019). Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels. EFSA Journal 17(4):5662. (opens in a new tab)Evidence: Regulatory assessmentRead: PMC full text, in Chrome (16 Oct 2026, for the almonds page)