Hydrogen Cyanide in Sweet potatos

by (80) Updated February 28, 2011 at 1:11 PM Created February 25, 2011 at 3:58 PM

Hi there!

I just stumbled across the the information, that sweet potatos contain Hydrogen Cyanide (HCN).

According to the german (did not see it in the english entry) Wikipediaentry, the amount of HCN in one potato is "toxigological relevant".

so, three questions:

1) how true/important/dangerous ist that matter? Or in other words: Do I have to care about that stuff at all?

2) can one reduce the amount of HCN by cooking, to a significnat lower amount?

3) is there still some food to find on this planet, that does not contain the one or the other (natural) ingredient, that is potentially harmfull for the human body? (This is a tiny bit ironically, but just a tiny bit)

I would be happy about response! Byebye

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8 Replies

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18909 · February 26, 2011 at 2:44 PM

Over 2500 species of plant contain cyanide in the form of cyanogenic glycosides. The cyanide molecule is in a compound with a sugar molecule. This is the storage form and is not toxic to the plant. When the plant cells are damaged the cyanogenic glycosides come into contact with an enzyme that releases the cyanide as hydrogen cyanide. This is a defensive measure against against being eaten.

Cyanogenic glycosides also break down during food preparation and processing releasing hydrogen cyanide. The hydrogen cyanide is not stable in heat and does not survive cooking methods such as baking, boiling and roasting. It can also be removed by fermentation.

Sweet potatoes do contain a very small amount of cyanogenic glycosides as do other plants eaten as food. It is not enough to be harmful even if you ate the sweet potato raw. However sweet potatoes are normally cooked anyway before being eaten and this will remove the tiny amounts of cyanide before you eat them.

A few food plants like bitter varieties of cassava, bitter almonds and bamboo shoots require careful processing due to the high levels of cyanogenic glycosides. Compared to these the tiny amounts of cyanide containing compounds in sweet potatoes is just not relavent, this is why there is little information about it.

  1. It is true. It is not dangerous. You do not need to worry about it.

  2. Cooking will elimintate most of what is there. Sweet potatoes are better cooked for other reasons anyway.

  3. Most edible foods contain compounds that in a high enough dose could be harmful however they usually harmless in the amounts found in foods.

Enjoy your sweet potatoes without worry :)


I could not find a single scientific paper on cyanide in sweet potatoes, it is just not important enough. A couple of books on google books mention the subject.

The food safety hazard guidebook

Medical biochemistry

55320 · February 25, 2011 at 4:09 PM

There was a king reigned in the East:
There, when kings will sit to feast, 60 They get their fill before they think
With poisoned meat and poisoned drink.
He gathered all the springs to birth
From the many-venomed earth;
First a little, thence to more, 65 He sampled all her killing store;
And easy, smiling, seasoned sound,
Sate the king when healths went round.
They put arsenic in his meat
And stared aghast to watch him eat; 70 They poured strychnine in his cup
And shook to see him drink it up:
They shook, they stared as white’s their shirt: Them it was their poison hurt.
—I tell the tale that I heard told. 75 Mithridates, he died old.

116 · February 26, 2011 at 7:08 PM

There seems to be no clear informations, just as Matthew said, to this matter. Some sources say, that the HCN tuns into gas due to heating, other say it goes into the cooking water (what happens if there is no water, if you make it in the oven/steamer) and some say it simply breakes up by heating/Cooking.

Seems that it is really too unimportant to provide more information! Nevertheless would it be interesting to know the "optimal" preparation method to eliminate the HCN most effective!

116 · February 26, 2011 at 4:37 PM

interesting topic and interesting answers!

after reading this, I googled a bit and found this: "Raw sweet potatoes, like raw lima beans, contain cyanogenic glycosides, natural chemicals that break down into hydrogen cyanide in your stomach or when the potato is heated. If you pierce the potato while it is baking or leave the lid off the pot while it is boiling, the hydrogen cyanide (a gas) will float off harmlessly into the air."

This brought me to the following: If you leave the pot open while boiling, the water will boil away. This means, you have to do a lot of water into the pot so that the potatos are more than covered, and there is still water in the pot after 30 mins of cooking.

So far so good, but an often given advice is to cook potatos with minimum water, in a covered pot, in order to minimize the loss of nutrients into the water. I`m not sure if this is a myth or if the nutrients really pass into the water. If they do, then cooking them, covered in much water, will lead to a larger loss of nutrients that cooking them with minimum water in a covered pot.

Hmm..cyanid and lots of nutrients or no cyanid and less nutrients:-(

This potato begins to cause trouble!

18383 · February 25, 2011 at 4:10 PM

As to your ironical question, pretty much all plant foods have some toxin or other, as a defense mechanism -- they can't run away. So pastured ruminants is probably the safest.

80 · February 28, 2011 at 1:11 PM

I don`t want to overstress this thing, but one questions seems still to be of interest. If one would know how the Hydrogen Cyanide is released while the cooking process, this would at least make it possible to adjust the preparation method.

If the HCN is released as a gas into the air=> cook without to cover with enough water to cover it/Bake it in the oven.

If the HCN goes into the cooking water => cover while cooking (and don´t drink the cooking water;-))/not sure about baking...

This would be interesting for most of the people here I guess.

933 · February 26, 2011 at 2:40 PM

From what I've read, "just don't eat the sweet potato raw". That's the only time there seems to be a problem of toxicity. Cooking it seems to deactivate the toxin. Munch on with joy and an easy conscience. :)

80 · February 26, 2011 at 11:53 AM

no one with information about this? I wonder! I mean its not "just" about lectins or phytates, its about cyanide in on of our favorite carb. And I guess I do not have discovered with this matter something completly new and unknown to the paleo folks.

There are a lot of infos about the cyanide content of Cassava, but not about sweet potato.

I just want to eat my sweet potato without a bad feeling...

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