TempoLife › Features › Food compounds: acid load, purines, oxalate and histamine › cyanogenic-glycosides
Cyanogenic glycosides: apricot kernels, cassava and bitter almonds
A cyanogenic glycoside is cyanide with a safety catch: the plant stores it bound to a sugar, keeps the enzyme that would release it in a separate compartment, and the two only meet when something chews or crushes the tissue. That defence works on insects, and it works on people.
This is a genuine acute toxicity, not a sensitivity. Do not eat raw bitter apricot kernels or bitter almonds: they are not a food, and “vitamin B17” or laetrile is not a vitamin and not a cancer treatment — a Cochrane review found no evidence of benefit and documented cyanide poisoning among the harms. Suspected cyanide poisoning — headache, dizziness, confusion, breathlessness, collapse after eating kernels or unprocessed cassava — is an emergency: call the emergency number or a poisons centre immediately. This page is not a diagnosis and not a treatment.
How the mechanism works, and why bitterness is the signal
Amygdalin in bitter almonds and in the kernels inside apricot, peach and cherry stones, linamarin in cassava, and related compounds in lima beans, bamboo shoots, elderberry and linseed are all inert as stored. Crushing the tissue brings the glycoside together with a β-glucosidase enzyme, the sugar is cleaved off, and hydrogen cyanide is released. Chewing does this in the mouth; so does grinding, blending or mashing.
Cyanide blocks the enzyme cells use to burn oxygen, so the effect is a cellular suffocation: headache, dizziness, nausea and confusion at lower exposures, and at higher ones breathlessness, collapse and death. Children are at much greater risk for the plain reason that the dose is per kilogram of body weight, and they weigh less.
Bitterness is the practical signal. Sweet almonds — the ordinary kind — contain very little amygdalin; bitter almonds contain a great deal, and they taste it. The same holds for cassava: bitter varieties carry far more than sweet ones, which is precisely why traditional processing for bitter cassava is elaborate and traditional processing for sweet cassava is not.
Apricot kernels and the laetrile story
Raw bitter apricot kernels are sold as a supplement, often under the invented name “vitamin B17” and with a claim that they treat cancer. There is no vitamin B17. Laetrile is a semi-synthetic derivative of amygdalin, it was tested, and it did not work; a Cochrane systematic review concluded there was no reliable evidence of benefit and noted the risk of serious cyanide toxicity. Poisonings from kernels bought as a supplement are documented in the medical literature and in national poisons-centre reports.
European food safety authorities have assessed the exposure specifically. The conclusion, in plain terms, is that the number of raw bitter kernels an adult can eat before exceeding the acute reference dose is very small — a small handful is already too many — and for a small child it is smaller still. The published figures belong with the opinions they came from and are not reproduced here; the point that matters is the scale, not the decimal.
None of this touches the apricot itself. The flesh of the fruit contains no meaningful amount, and neither does an ordinary sweet almond, an apple you ate around the core, or a marzipan made to food standards, where bitter almond content is controlled precisely because of this compound.
Processing: what removes it and what does not
Cassava is the case where processing is a matter of public health rather than cookery. Bitter varieties are made safe by a sequence — peeling, grating or pounding to bring enzyme and glycoside together, then prolonged soaking or fermentation to let the cyanide escape, then sun-drying or thorough cooking. Skipping steps, usually under pressure of drought or famine, is what produces the outbreaks of konzo, an irreversible paralytic disorder, that are documented in parts of Africa.
Bamboo shoots must be boiled; raw or lightly cooked shoots are genuinely toxic, and the boiling water is discarded. Elderberries need cooking, and the leaves, stems and unripe berries should not be used at all — raw elderberry juice has caused documented outbreaks of illness. Lima beans require thorough boiling in the same way as other dried beans.
Linseed is the everyday case: whole and ground linseed contains cyanogenic glycosides at levels that are not a concern in the amounts normally eaten, and baking or boiling reduces them further. The advice that exists is about moderation of large quantities of raw linseed, not about avoiding it in bread.
What does not work is assuming heat alone is enough. Volatilising cyanide requires the enzyme to have acted and the gas to have somewhere to go — which is why soaking, fermenting and discarding the water are so central, and why a quick fry of unprocessed bitter cassava is not a preparation method.
Cyanogenic glycosides by food group
Bands, not decimals. Where a published quantity for a specific food could not be verified against a document, this surface prints the band rather than a number — and every food below links to its own nutrition page so you can see what else is in it.
| Category | What it means | Examples |
|---|---|---|
| Do not eat raw — real acute hazard | These carry enough releasable cyanide to poison. Bitter apricot kernels and bitter almonds are not food at all; the others are food only after proper processing. | Bitter apricot kernels sold as “vitamin B17” or laetrile, Bitter almonds, Cassava, raw, Bamboo shoots, Elderberry, Baby lima beans, cooked |
| Processing that makes them safe | The sequence matters more than any single step: bring enzyme and glycoside together, then give the cyanide time and water to leave. | Peel, grate, soak or ferment, then dry or cook cassava thoroughly, Boil bamboo shoots and discard the water, Cook elderberries; never use leaves, stems or unripe berries |
| Fine as normally eaten | The fruit flesh, the ordinary sweet almond, and linseed in the quantities anyone actually eats. These are not the same thing as the kernel inside the stone. | Apricot, Almonds, Apple, Flax seeds, Sour cherry |
What changes the number
- Crushing, grinding and chewing are what release the cyanide — intact seed passes through largely unchanged.
- Soaking and fermentation let the released cyanide escape, which is why traditional cassava processing takes days rather than minutes.
- Boiling and discarding the water works for bamboo shoots and beans; frying unprocessed bitter cassava does not.
- Bitterness tracks the content closely enough to be a usable warning in almonds and cassava.
- Body weight sets the risk, which is why children are affected by amounts an adult would tolerate.
Talking to someone who can actually test
Nothing on this surface is personal medical advice. If a food genuinely makes you ill, if you have had a kidney stone or a gout attack, or if you are considering removing a food group from your diet, the person to talk to is your doctor, pharmacist or a registered dietitian — they can test for the things that can be tested for, which a table cannot.
Sources: European Food Safety Authority — scientific opinions on cyanogenic glycosides in food, including raw apricot kernels and other food sources. · Cochrane systematic review of laetrile treatment for cancer, which found no reliable evidence of benefit and documented cyanide toxicity. · World Health Organization and food-agency guidance on cassava processing and the prevention of konzo. · Food names and links: the site food database. Checked 2026-09-06.
Frequently asked questions
Are apricot kernels a cancer treatment?
No. Laetrile and so-called “vitamin B17” were tested and a Cochrane systematic review found no reliable evidence of benefit, alongside documented cyanide poisoning. There is no such vitamin.
How many raw bitter apricot kernels are dangerous?
Very few. European assessments concluded that an adult exceeds the acute reference dose after only a small number of raw bitter kernels, and a small child after fewer still. The safe number to plan around is none.
Are ordinary almonds a risk?
No. Sweet almonds — the ones sold as food — contain very little amygdalin. Bitter almonds are a different thing entirely, which is why their use in food is controlled.
Is linseed safe?
Yes, in the amounts people actually eat. It contains cyanogenic glycosides, but the levels are not a concern at normal intakes and baking or boiling reduces them further. The advice is about very large quantities of raw linseed, not about seeds in bread.
Why does cassava need such elaborate preparation?
Because bitter varieties carry a lot of linamarin, and making them safe requires bringing the enzyme into contact with it and then giving the cyanide time and water to leave — peeling, grating, soaking or fermenting, then drying or thorough cooking. Skipping steps has caused outbreaks of irreversible paralysis.
Other compound pages
Phytate
People with low iron or zinc, and anyone eating mostly unleavened wholegrain food
Lectins
Anyone who cooks dried beans; anyone who has met a “lectin-free” diet
Glycoalkaloids
Everyone who stores potatoes; anyone who has heard nightshades are dangerous
Goitrogens
People with thyroid disease, and anyone in a region with marginal iodine intake
Acid load (PRAL)
Kidney stone formers, chronic kidney disease, and anyone who has met the “alkaline diet”
Food pH
Home canners and picklers, anyone with dental erosion, anyone confused by “alkaline foods”
Skip the miracle, keep the fruit
Apricots are good. The kernels are not a supplement. TempoLife is for tracking the ordinary food that actually adds up.