# Poisonous when cooked **URL:** \ **Category:** Factual Questions\ **Created:** [August 7, 2011, 6:48pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849 "2011-08-07T18:48:42Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [August 7, 2011, 6:48pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/1 "2011-08-07T18:48:42Z")
There are a number of foods which are poisonous when raw but safe to eat when cooked. Are there any which are safe to eat when raw but poisonous when cooked? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [August 7, 2011, 7:03pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/2 "2011-08-07T19:03:13Z")
Castor beans. When whole and uncooked, the hard capsule prevents it from being digested, but if you were to cook the beans, breaking open this capsule, you’d be able to be poisoned by the [ricin](http://en.wikipedia.org/wiki/Ricin)inside the pulp. (Castor oil is made from the beans, but has no ricin, and is perfectly safe to consume.) ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [August 7, 2011, 7:07pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/3 "2011-08-07T19:07:20Z")
Overcooking meat generates carcinogenic substances called polycyclic aromatic hydrocarbons, though experts differ on whether consuming them increase your cancer risk significantly or only a bit. ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [August 7, 2011, 7:29pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/4 "2011-08-07T19:29:32Z")
> [@WhyNot](#): > > Castor beans. When whole and uncooked, the hard capsule prevents it from being digested, but if you were to cook the beans, breaking open this capsule, you’d be able to be poisoned by the [ricin](http://en.wikipedia.org/wiki/Ricin)inside the pulp. > > (Castor oil is made from the beans, but has no ricin, and is perfectly safe to consume.) Are the beans themselves actually eaten whole? If so, I don’t think they count for the purpose of my question. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [August 8, 2011, 3:17am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/5 "2011-08-08T03:17:03Z")
> [@psychonaut](#): > > Are the beans themselves actually eaten whole? If so, I don’t think they count for the purpose of my question. I wondered that, myself. 😕 ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [August 8, 2011, 3:36am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/6 "2011-08-08T03:36:01Z")
Since cooking usually denatures proteins except in some cases like with prions I think the answer would have to be “no”. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 8, 2011, 7:26am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/7 "2011-08-08T07:26:50Z")
> [@psychonaut](#): > > Are the beans themselves actually eaten whole? AFAIK, they’re not deliberately eaten at all - the ‘eating whole’ thing is advice about accidental ingestion of the seeds of the plant when grown as an ornamental. ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [August 8, 2011, 8:10am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/8 "2011-08-08T08:10:51Z")
Googling led me to an article “[On Eating Raw Mushrooms](http://www.mykoweb.com/articles/EatingRawMushrooms.html)” which makes the following claim: > [@](#): > > Other methods of chemical cooking, aside from citric acid, involve brining or pickling. I lack personal experience with this form of mushroom processing, but I have heard and read it is used to apparently satisfactory effect in many cultures, notably Russia, where many kinds of freshly collected _Russula_ and _Lactarius_ species are reportedly tossed collectively into the brine barrel, to be directly retrieved and munched later. Of interest with this method is that some of these species so prepared are considered poisonous when cooked by conventional heat application. So we have a somewhat vague claim that certain unspecified edible species of mushrooms are “considered” poisonous when cooked. Can any Doper mycologists confirm this and provide further details? ---
**Author:** ![armedmonkey](https://avatars.discourse-cdn.com/v4/letter/a/d6d6ee/32.png) [@armedmonkey](https://boards.straightdope.com/u/armedmonkey)\ **Post date:** [August 8, 2011, 8:26am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/9 "2011-08-08T08:26:37Z")
> [@astro](#): > > Since cooking usually denatures proteins except in some cases like with prions I think the answer would have to be “no”. But the toxins don’t necessarily have to be proteins. [Wikipedia’s entry for rhubarb](http://en.wikipedia.org/wiki/Rhubarb) says “Cooking the leaves with soda can make them more poisonous by producing soluble oxalates.” Oxalate isn’t really that poisonous (give you kidney stones, though), and you don’t eat the leaves, but the above illustrates that there are compounds in plants that aren’t proteins and yet are toxic. And some may change to a more toxic form when heat is applied. Another common example of a non protein plant toxin would be Strychnine, which is an alkaloid. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 8, 2011, 8:28am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/10 "2011-08-08T08:28:21Z")
> [@psychonaut](#): > > So we have a somewhat vague claim that certain unspecified edible species of mushrooms are “considered” poisonous when cooked. Can any Doper mycologists confirm this and provide further details? IANAMycologist, but I think I’m right in saying that most non-edible _Lactarius_ and all non-edible _Russula_ aren’t poisonous so much as variously unpalatable due to peppery or bitter flavours\* - so it could be that brining/pickling fixes that, rendering them edible. (\*Despite this apparent ‘rule of thumb’, there really aren’t any safe generalisations when it comes to mushroom picking - careful identification of species is the only truly reliable way) ---
**Author:** ![armedmonkey](https://avatars.discourse-cdn.com/v4/letter/a/d6d6ee/32.png) [@armedmonkey](https://boards.straightdope.com/u/armedmonkey)\ **Post date:** [August 8, 2011, 8:42am UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/11 "2011-08-08T08:42:15Z")
Found one. Oddly enough, it’s kidney beans. [From Here](http://www.food-info.net/uk/tox/beans.htm) > [@](#): > > It has been shown that heating to 80°C may potentiate the toxicity five-fold, so that these beans are more toxic than if eaten raw. In studies of casseroles cooked in slow cookers, internal temperatures often did not exceed 75°C. To be fair, if cooked _properly_ there is no danger, but it’s the closest I can find. Incidentally, the toxin is Phytohaemagglutinin - a lectin protein. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 8, 2011, 4:29pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/12 "2011-08-08T16:29:26Z")
I’ve eaten kidney beans cooked to higher temperatures plenty of times. It must not be much of a toxin, even potentiated five-fold. ---
**Author:** ![Ferret\_Herder](https://avatars.discourse-cdn.com/v4/letter/f/e47774/32.png) [@Ferret\_Herder](https://boards.straightdope.com/u/Ferret_Herder)\ **Post date:** [August 8, 2011, 4:37pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/13 "2011-08-08T16:37:40Z")
> [@Chronos](#): > > I’ve eaten kidney beans cooked to higher temperatures plenty of times. It must not be much of a toxin, even potentiated five-fold. The problem is that they were cooked at a sub-boiling temperature; the [lectin in question](http://en.wikipedia.org/wiki/Phytohaemagglutinin) is destroyed if boiled. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 8, 2011, 4:43pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/14 "2011-08-08T16:43:23Z")
Ah, so there’s only a relatively narrow range of dangerous temperatures, then. ---
**Author:** ![randomface](https://avatars.discourse-cdn.com/v4/letter/r/5fc32e/32.png) [@randomface](https://boards.straightdope.com/u/randomface)\ **Post date:** [August 8, 2011, 5:05pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/15 "2011-08-08T17:05:24Z")
There is a joke somewhere in here about my wife’s cooking… Seriously though, can’t some poisonous compounds be dissolved out of the pits of stone fruits? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [August 8, 2011, 5:09pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/16 "2011-08-08T17:09:25Z")
I would guess that the possibility that the shell of a bean is damaged in some way would be a concern even swallowing the beans whole. Castor beans are toxic enough that the lethal dose for a human is 4 - 8 beans. I’m not sure I’d consider castor oil “perfectly safe”, actually. It’s used as a food additive in small quantities, and as a laxative. A large dose of it is nasty: > **[Castor oil](https://en.wikipedia.org/wiki/Castor_oil#Use_as_a_means_of_intimidation_in_Fascist_Italy)** > > Castor oil is a vegetable oil pressed from castor beans. > It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is 313 °C (595 °F) and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about 90% of fatty acids are ricinoleates. Oleic acid and linoleic acid are the other significant components. > Castor oil and its derivatives are used in the manufacturing of soaps, lubricants, hydraulic and brake fluids, paints, dyes, coatings, inks, co... ---
**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\ **Post date:** [August 8, 2011, 5:45pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/17 "2011-08-08T17:45:26Z")
> [@Chronos](#): > > I’ve eaten kidney beans cooked to higher temperatures plenty of times. It must not be much of a toxin, even potentiated five-fold. Well, your one cup of Kidney bean stew cooked at the improper temperature would be as toxic as 5 cups of bean salad, which is to say, not really noticeably toxic at all. ---
**Author:** ![Swords\_to\_Plowshares](https://avatars.discourse-cdn.com/v4/letter/s/b38774/32.png) [@Swords\_to\_Plowshares](https://boards.straightdope.com/u/Swords_to_Plowshares)\ **Post date:** [August 8, 2011, 5:49pm UTC](https://boards.straightdope.com/t/poisonous-when-cooked/591849/18 "2011-08-08T17:49:40Z")
Unless you consider the aftermath on the porcelain throne toxic…