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I was at lunch today and the conversation turned to almonds and their cyanide content. One co-worker said almonds contain a lot of cyancide and the number of almonds that can kill you surprisingly low.

Caution almonds

My question is "how low"? They couldn't answer, except to say it's low.

After a quick google search I found this link that says the number is 15. FIFTEEN!!! I've had about that many almonds today... so that can't be right. And that link is from a questionable source (google+) but I've heard this urban legend before.

How many almonds will it take to kill a human? I'm looking for LD50 of a 70kg person.

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With bitter almonds, 8 - 32 almonds will give you the lethal dosage of cyanide. Bitter almonds yield about 6.2 mg of cyanide per almond and the LD50 for cyanide is 50 mg - 200 mg.

This applies only to bitter wild almonds: considering that you're not dead, you most likely ate domesticated sweet almonds, which apparently do not have this problem. The sale of wild almonds may be illegal, in fact, though I can only find blogs and internet comments alluding to this.

From wikipedia

Wild almonds are bitter, the kernel produces deadly cyanide upon mechanical handling, and eating even a few dozen at one sitting can be fatal.

...

While wild almond species are toxic, domesticated almonds are not;

  • It might bear mentioning that sweet almonds still contain some hydrocyanic acid, apparently as much as 25 mg/kg (8mg/kg standard deviation). However, it would take at least 2 kg of almonds (roughly 1650 kernels) to reach a lethal dose, which is highly unlikely to be digested unintentionally. – Jonathan Y. Feb 24 '15 at 11:23
  • @JonathanY. That is an interesting comment. And yeah, given that I usually only consume up to 1 lb of steak, and that's my favorite food, I doubt anyone could even unintentionally digest 2 kg of anything. – Avi Feb 24 '15 at 11:29
  • I concur. Except maybe cake :) (they do put almonds in cakes, though, and I don't know whether baking breaks down hydrocyianic acid.) It might be interesting if anyone could comment on that. Also, the time-frame within which a lethal dose needs to be digested for adverse effects to appear, before the acid metabolizes. – Jonathan Y. Feb 24 '15 at 11:36
  • 2
    @JonathanY.: Firstly, nowadays using almond arome (benzaldehyde without cyanide) is far more common than using bitter almonds. Secondly, cyanide is not very stable, it is easily oxidized into cyanate which is of far less concern. Thirdly, we do have an enzyme, rhodanase, which oxidizes CN- to thiocyanate for detoxification, wikipedia says it has a capacity of about 0,1-1 mg/(kg bw * h) as long as sufficient sulfur is available. Recipes use maybe 5 bitter almonds / kg of dough/marzipan, i.e. about 30 mg CN-/kg. So again, you'd need to eat unfeasible amounts to get in danger. – cbeleites supports Monica Jun 1 '17 at 17:25
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This is an addition to Avi's answer.

The varieties are sweet and bitter almond (the latter is the one with amygdalin which is the source of the cyanide as well as the aroma (benzaldehyde)) almonds, see http://en.wikipedia.org/wiki/Almond#Sweet_and_bitter_almonds.

Here (Germany) bitter almonds are sold only in small amounts for baking which are labelled that they are not for raw consumption, and are to be kept away from children. Here's a newspaper article from 1964 about a discussion whether the allowed package size should be reduced to 50 g (which is AFAIK the currently available package size). The article argues that till then the opinion was the awful taste provides enough safety. For the counter argument they cite a number of studies that conclude many people are really bad at smelling and tasting, and that the knowledge about the bitter almonds in the population was decreasing.

However, smelling of cyanides has been studied a lot in the 1950s and 60s, and huge differences in the human "limit of detection" and substantial numbers of people who do not smell cyanide have been found (Literature list 1 Literature list 2). Also how people describe the smell of cyanides differs a lot (not surprisingly, as at least in western cultures, smells are hardly described at all, so talking about smells is difficult, and also considering the huge differences in smelling sense between people).

Personally, I smell cyanide, and I perceive the smell of the cyanide as very different from the smell of the benzaldehyde (almond aroma, amaretto, ...) which are both released by hydrolysis of the amygdalin. I never tried tasting bitter almonds (only smelling, e.g. mashing them with water, and if you like to separate the cyanide smell from the benzaldehyde smell, with a small amount of an odorless acid)
Even if you happen not to be able to smell cyanide, the benzaldehyde content is very remarkable compared to sweet almonds. So if the almonds you ate tasted and smelled like "normal" almonds, you ate sweet almonds.

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protected by Community Sep 10 '13 at 9:15

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