Poisonous Plants: Lima Beans

I don’t recall being a picky eater as a child, but one food I could barely stomach was lima beans. The smell, the texture, the taste, even the look of them, really didn’t sit well with me. I know I’m not alone in this sentiment. Lima beans are a popular thing to hate, and I have avoided them ever since I was old enough to decide what was allowed on my plate. To be fair, the only lima beans I remember trying were the ones included in the familiar bag of frozen mixed vegetables, which might explain why I didn’t like them. But little did I know there is another reason to avoid them – lima beans are poisonous.

That’s a strong statement. In case you’ve eaten lima beans recently or are about to, I should ease your concerns by telling you that you have little to worry about. Commonly cultivated lima beans are perfectly safe to eat as long as they are cooked properly, and even if they are eaten raw in small doses, they are not likely to hurt you. But again, why are you eating lima beans? They’re gross.

lima beans in cans

Phaseolus lunatus – commonly known as lima bean as well as a number of other common names – is in the legume family (Fabaceae) and is native to tropical America. It is a perennial, twining vine that reaches up to 5 meters. It has trifoliate leaves that are alternately arranged, and its flowers are typically white, pink, or purple and similar in appearance to pea flowers and other flowers in the legume family. The fruits are hairy, flat, 5 – 10 cm long, and often in the shape of a half moon. The seeds are usually smooth and flat, but are highly variable in color, appearing in white, off-white, olive, brown, red, black, and mottled.

P. lunatus experienced at least two major domestication events – one in the Andes around 4ooo years ago and the other in Central America more than 1000 years ago. Studies have found that the first event yielded large seeded varieties, and the second event produced medium to small seeded varieties. Wild types of P. lunatus have been given the variety name sylvester, and cultivated types are known as variety lunatus; however, these don’t appear to be accepted names by plant taxonomists and perhaps are just a way of distinguishing cultivated plants from plants growing in the wild, especially in places where P. lunatus has become naturalized such as Madagascar.

Distinguishing wild types from cultivated types is important though, because wild types are potentially more poisonous. Lima bean, like several other plants we eat, contains compounds in its tissues that produce cyanide. These cyanide producing compounds are called cyanogenic glucosides and are present in many species of plants as a form of defense against herbivores. The predominant cyanogenic glucoside in lima beans is called linamarin, which is also present in cassava and flax.

Fruits of lima bean (Phaseolus lunatus) - photo credit: wikimedia commons

Fruits of lima bean (Phaseolus lunatus) – photo credit: wikimedia commons

In order for lima beans to poison you, they must be chewed. Chewing brings linamarin and the enzymes that react with it together. Both compounds are present in the cells of lima beans, but they reside in different areas. Once they are brought together, a reaction ensues and hydrogen cyanide is produced. Because cyanide isn’t produced until after the plant is consumed, the symptoms of cyanide poisoning can take a little while to occur – often several hours.

Cyanide poisoning is not a pretty thing. First comes sweating, abdominal pain, vomiting, and lethargy. If the poisoning is severe, coma, convulsions, and cardiovascular collapse can occur. There are treatments for cyanide poisoning, but if treatment comes too late or if the dose is large enough, death results.

Cassava (Manihot esculenta) is particularly well known for its history of cyanide poisonings. It is a staple crop of people living in tropical areas of Africa and South America. Humans can readily metabolize small amounts of cyanide, and processes like crushing and rinsing, cooking, boiling, blanching, and fermenting render cassava safe to eat. However, consuming cassava that isn’t prepared properly on a consistent basis can result in chronic illnesses, such as konzo, which is a major concern among cultures in which cassava is an important food source.

I guess I should reiterate at this point that most cultivated lima beans contain low (read “safe”) levels of cyanogenic glucosides and, particularly when cooked, are perfectly safe to eat. I’m still not totally convinced that I should eat them though. While researching this article I came across numerous sites claiming that lima beans are delicious while offering various recipes to prove it. I even came across this story in which a self-proclaimed “lima bean loather” was converted to the side of the lima bean lovers. I don’t fancy myself much of a cook, so I’m hesitant to attempt a lima bean laden recipe for fear that it will only make me hate them more. If anyone out there thinks they can convince me otherwise with their tasty creation, be my guest.

And now a haiku:

You are lima beans
I despised you as a child
Perhaps unfairly?

Follow these links to learn more about cyanide producing crops and lima beans:


24 thoughts on “Poisonous Plants: Lima Beans

  1. I am not a fan of Lima beans either. Had no idea they were poisonous. I have not purchased that “mixed veggie bag” for a long time. Very fun and interesting read. (:

  2. Interesting read (I didn’t know about linamarin in flax!); I’m not sure I’ve ever tried Lima beans, but if I do and stumble across a good recipe, I’ll forward it.

    One of the most curious things I learnt while researching cassava-related intoxications is that herbivores’ (and our own) capacity for detoxifying cyanogenic compounds isn’t a fixed value, but that it largely depends on the availability of sulphur-rich proteins (eg. fish) in the diet: as the authors of a paper put it, “What is ‘‘safe’’ depends on intake of sulphur-rich proteins and other nutrients”.

    Toxic stuff; so fascinating!

    • Thanks for the insight, Aina. Toxic stuff really is fascinating, especially the idea that not everyone is necessarily affected the same and that much depends on diet, genetics, tolerances, etc.
      If you do try lima beans and like them, I’d be happy to receive the recipe.

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  7. Marzipan is not readily available in South Africa but the alternative we get is made from Lima beans ….. presumably not cooked! I still enjoyed my Christmas cake and the taste was almost indistinguishable from almonds !

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  9. I’ve always loved Lima beans. In the Army, maybe 1 out of 8 C-Ration packs contained Lima beans & Ham. Being a fast eater, I scarfed down whatever I got, then waited for the poor Lima bean-haters to start whining. When they wanted to trade, I didn’t have anything to trade, except maybe dessert, so I usually got 2 or 3 cans of Lima beans for free.
    This made Basic Training a little like Heaven, I’m sure.

  10. I also don’t soak my beans, either. I just rinse and dump into the slow cooker. Here is my own recipe, such as it is:
    Lima Beans & Ham – Lazy Old Fat Guy recipe
    1 pound dried lima beans
    8 cups water
    1 lb. canned ham – Dutch Colony
    2 Tbsp vegetable oil
    Additional water, as needed to cover
    2 Tbsp onion powder or 4 Tbsp minced
    1/2 teaspoon garlic powder
    1/2 teaspoon black pepper
    1 tsp salt
    3 tsp chicken bouillon granules


    Turn on slow cooker to High
    Rinse Lima beans and place into slow cooker
    Add 8 cups water
    Open canned ham, dump into large sauce pan, and bust it up with a wooden spoon
    Add oil, stir and cook at medium high heat until brown
    Pour ham into slow cooker
    Add rest of ingredients and cook for 4-6 hours on High, or until tender. Add water to keep beans covered.
    Ask wife to leave town for 3 or 4 days.

  11. Bean poisoning is a real thing. I didn’t know about it but one time i ate about a pound of fresh green beans. They were a variety called Hopi purple string beans. They were all there was to eat that day. I mean, i could have gone begging, but no.
    I vomited for hours. It was horrible. I was young and recovered in about a day. It could easily kill an old or infirm person.

    • The wonderful aroma and taste of Lima Beans is sublime. I ate all the C-ration Lima Beans & Ham I could in the Army. None of the other guys had such discerning palates, so I usually got 4 or 5 cans whenever we ate boxed meals.

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