October 1, 2002

My sister & niece in Germany swear that raw green beans are poisonous.

Would appreciate your advice. I could only find info on prussic acid being toxic to cattle on google.com.

Here are the excerpts they sent from 4 web sites in Germany, as best I could translate them:

Raw beans are poisonous because they contain prussic (hydrocyanic) acid, which is rendered not dangerous only by cooking. It was only in 1957 that prussic acid protein was discovered in green beans. A few hours after eating raw beans or bean seeds, some individuals become sick from low blood pressure, vomiting, stomach ache, circulation problems, convulsions, or heart palpitations. These poison symptoms are possible with all beans. The susceptibility to these reactions to beans is heriditary.

Because they contain protein - Phasin?, raw beans can result in nausea and vomiting in sensitive people, which can be disrupted by heat.

Green beans nourish the blood and strengthen the nerves and bones. They help reduce high blood pressure and improve the function of insulin. However, they cannot replace medical treatments for diabetes. They are prophylactic/preventive. Correct preparation: Always eat green beans cooked or steamed -- as a side dish or a salad. Careful: raw beans are poisonous.

Plant poisonings are the most common cause of calls to the poison control center. Poisonous plants include arnica, Aronstab, henbane, raw green beans, holly, dieffenbachia, yew, monkshood, foxglove (digitalis), laburnum, autumn crocus, cactus with poisonous spines, lupine, cockchafer, narcissus, oleander, castor, poppy, hemlock, thornapple, deadly nightshade, Christmas star, meadow hogweed, bryony, green and unripe potatoes, green pieces of grown potato tubers lying on the ground, and also green, unripe tomatoes and many other flowers and berries.


Sarah Forsman

October 06, 2002

Dear Sarah,

I want to answer your question to the best of my ability but first I have to know whether you are referring to the green beans that are sometimes also called "string beans". They are long and slender. They look more like a vegetable than a bean. Are those the beans that you are referring to because it is not at all clear. I'm wondering if, in Europe, they are referring to some other beans as "green beans"?

Awaiting your clarification.


Dear Rhio,

Thanks for your response. I think you may be right that they were referring to other green beans than string beans. I was assuming string beans when my niece and sister said raw green beans, but a response I got from Dr. Dan Brown of Cornell addressed a wide variety of "green beans". He had issues with only raw lima or butter beans as you can see from his response which I've attached below. FYI, if you're not familiar with it, this web site at Cornell contains useful information about poisonous plants: http://www.ansci.cornell.edu/plants/

Would still be curious to hear your opinion when you have a chance.

Thanks and regards,

Sarah Forsman

From: Dan Brown [mailto:dlb20@cornell.edu]
Sent: Friday, October 04, 2002 11:44 AM
To: Sarah Forsman
Subject: Re: raw green beans poisonous?

I think all plants might have a little cyanide as part of normal metabolism, but this is usually not a problem due to the small amounts involved. Most beans have a little, but the older, darker type of lima or butter beans have quite a bit. The modern white varieties have very little. When it exists in raw beans, cyanide is mostly bound to other chemicals as a cyanogen, which can release the cyanide when reacted with an enzyme also present in the plant. If the plant is injured or frozen, cell structures burst that normally keep the cyanide separate from the cyanogen and CN can be relased. In some plants, at some dosages, this can harm livestock or humans eating the material.

This doesn't happen as often as you might think though because we soak, cook and dry foods like casava and beans so the CN is driven off into the air. Also, cooking can inactivate the enzyme so the realtivly indigestible cyanogens pass from us without releasing the cyanide. Most green beans would be OK to eat raw, but I would be careful about raw lima and butter beans of the old dark heirloom varieties, especially if wilted for a while before being eaten.


November 15, 2002

Dear Sarah,

Thanks for forwarding the information from Dan Brown. I think I learned more here than you did by writing me. I thought it was interesting when he states "if the plant is injured or frozen, cell structures burst that normally keep the cyanide separate from the cyanogen and CN can {then} be released." I also consider that cooking is a form of injury to the plant, but maybe the heat deactivates the cyanide that is then released. Dr. Ernest Krebs of Canada has done extensive research on laetrile, also known as Vitamin B17 and nitriloside. He states that apricot seeds and other seeds that contain laetrile also contain a cyanide molecule that is only released if there is cancer in a body. Cancer cells secrete an enzyme that unlocks the cyanide at the site of the cancer and kills the cancer cells. If there is no cancer in the body, the cyanide just goes through without being released. This, of course, is a greatly simplified explanation of the process. You can find a link to Dr. Krebs site on my links page.

I eat a type of fresh green bean called the Fava Bean. I love them raw, and so far seem to have had no problems with them. But I am going to write to Dan also, and get more input.

As far as the "string beans" go, I have not had any trouble eating them raw, although I only eat them occasionally. I prefer the edible podded peas, but the string beans are supposed to be very alkalizing to the body.

Thank you for all the information,

With blessings,


July 2, 2006

Hi there,
I was just surfing the net looking for green bean toxicity when I came upon your article. The reason I’m looking is because my German friend was astonished and dismayed that I serve my green beans quite al dente quoting that they were poisonous if not well cooked. To clarify green beans in the German sense, yes, they do mean string beans. I knew about other beans being toxic, but never green beans. My husband and 4 year old son like to eat them just off the bush. I’ve never seen any adverse symptoms in either of them, but thought I’d see what I could find on the subject.
Interesting information on your web site.  Thanks!!

18 Aug 2006

Subject: Green Beans and are they poisonous


interesting opinions on the green beans issue. We had a discussion about it the other day because my kids love them raw and my dad said they contain "Blausaeure", sorry, do not know what that is in english. Clearly we are from Germany and there no one eats them raw. Interestingly enough when Germans cook green beans we would consider them overcooked in Canada. If you go on the net and look up the german sites they all say do not eat them raw.

We still do because they are nice and crunchy right off the plant.

Which brings me to another topic of discussion, when preparing the beans do you cut off both ends or just the end that is attached to the plant? Since modern beans no longer contain strings, I have made the practise of only cutting one end, how does everyone else do it?


August 7, 2006

Subject: string bean poison


In common with other beans the mature bean in string or runner bean (Phaseolus aborigineus) is definitely poisonous. In their mature state they contain Prussic (Hydrocyanic) Acid or Cyanogenic Aminoglycoside in quantity. 

In moderation eating them straight from the climber bush very very young tender beans should not be a problem but stressing again in MODERATION. Even young eaten in quantity the beans need thoroughly cooked /boiled to negate and potential poison. The cooking action neutralises the active part. Mature beans which have already turned purple are toxic whilst the outer casing has turned ' stringy ' and in any case is no longer fit to eat.
Nature warns us with this angry colour, the plant is protecting the seed product against mammals.

Take it from one who has experienced some quite severe symptoms of extreme fever, nausea + diarrhoea having inadvertently drunk the liquidated products as a raw smoothy. I required overnight hospitalisation drip feed and oxygen, it I were a child or old person it could have killed me.

They are right in Germany.

Clive Rogers

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