A Brief Overview: Cooking and sprouting legumes so they won’t cause gas (or kill you)

Published by emilyatspecklefarm on

 Ahh… the days of naive bean consumption!  We would put dry beans in a crock pot, add water and cook until done. Hours later  after dinner when we were bloated with gas, we would bemoan the random affects that eating beans sometime caused. Little did I know, we were poisoning ourselves with improperly cooked beans.

Legumes are plants in the fabaceae family (previously known as legumaceae) they have a flower that is self-fertile and enclosed, produce seeds inside of a pod and form symbiotic relationships with soil bacteria that fix nitrogen. This post is about cooking legumes so I won’t go any further into the botanical side of legumes. As a food they are highly nutritious, rich in protein, carbohydrates  and minerals. However, the legumes used for food also contain toxic compounds that need to be deactivated by soaking and cooking.

This is because mature legumes contain complex sugars called oligosaccharides and toxic proteins called lectins. Most mammals and birds cannot digest the oligosaccharides, they are part of the reason why eating legumes can cause gas and bloating. Your gut bacteria can digest those compounds. Your bacteria get  excited about the feast you just sent them, eat a whole bunch and make an unusually large amount of gas.  

Lectins and other enzyme inhibitors are more of a health concern though.  They interfere with normal digestion and metabolism, resulting in food poisoning like symptoms. Long term consumption can lead to protein deficiencies, weight loss and general poor health. Lectin poisoning has the potential to be fatal. 

 Depending on the species and variety, every bean will have a different amount of those compounds. The beans you normally eat raw as immature pods haven’t yet developed the compounds. So you don’t need to cook your green beans but as the beans mature they start to develop the compounds.  If you have beans that are beyond the green bean stage but can still be eaten fresh, they might contain some of the problematic compounds. I haven’t found anything that specifically addresses that issue so I would just cook them a little longer than green beans and make sure they are fully cooked before serving. Kidney beans are about the highest and lentils are one of the lowest for these problematic compounds. That doesn’t mean kidney beans are unsafe, you just need to make sure you cook them in the right way to deactivate the dangerous compounds.
The “safe five” that can be eaten without cooking still have those compounds but they are able to be deactivated/ digested to safe levels by sprouting.

All other beans, for safety and health benefits, should be soaked for 12 hours, then boiled uncovered for a minimum of 15 minutes and then simmering until fully cooked-tender. 
Some legumes once the pod and bean start to mature become toxic and inedible but are safely eaten when young and tender. Many other legumes are toxic regardless.  Castor beans for instance, are a legume that can be deadly poisonous. My point is, Don’t assume a plant that makes a bean is edible.

For ease of reference I’ve organized them by how they are safely eaten. The common name’s all link back to their Wiki page in case you want a little more general information about any of the legumes mentioned. I only have pictures of a few so I also provide a link to Bakers Creek Heirlooms. This is an awesome seed company, they have cooking and cultivation information, not to mention pictures, for most of the plants they offer seed for. I also include a few resources that go into a little further detail about the possible health risk of undercooked or improperly cooked legumes.

 Baker Creek Heirlooms

Living with Phytic Acid -Weston A. Price
FDA on poisoning by undercooked beans

Effect of Soaking and Cooking On the Oligosaccharides and Lectines in Red Kedney Beans. This PDF doesn’t show up online but it works fine when downloaded.

Dry legumes that must be cooked:

Soaked 12 hours, boil uncovered at least 15 minutes, then they can be finished in a crock pot or any other way.

 Common Bean (Phaseolus vulgaris) 
 Also known as: snap beans, string beans, field bean, flageolet bean and haricot bean. “Green beans” and the dry beans you usually eat, are in both this species. All the immature pods and beans of this species are safe to eat.
Some common varieties: pinto, white, black, kidney, cranberry, Kentucky wonder, wax, blue lake…there are many more varieties.

Tepary Beans (Phaseolus acutifolius)

Lima (Phaseolus lunatus)
Some varieties of lima beans have a cyanide compound so you should always cook lima beans thoroughly.

Soy Beans (Glycine max)
Soy beans have some especially nasty enzyme inhibitors and should never be eaten uncooked or fed to any animal in a raw form, even if they are green they should be thoroughly cooked or fermented. 

        Black Eyed Peas  (Vigna unguiculata unguiculata)
*update*: I just found out the leaves are edible and high nutritious, if you would like to read more check out Edible Cowpea Greens by Emily over at “Not Dabbling In Normal”
         Long Beans  (Vigna unguiculata  sesquipedalis) These are regularly eaten as young pods or dry beans

Runner Beans (Phaseolus coccineus)
These are a perennial that’s usually grown as an annual. Their root, as well as young pod and dry bean, can be eaten. 

 Broad Beans -fava beans (Vicia faba)
The pod and outer seed coat of immature fava beans are tough, and generally removed before eating, it will already be removed in dry fava beans.  Parboiling the beans for a minute allows the seed coat to be easily removed *it’s fine to leave the seed coat on if feeding to companion birds*  People who make a lower than normal amount of enzymes needed to metabolize two proteins made by fava plants suffer from Favism. If they consume fava beans or breath the pollen, their red blood cells are damaged.  Essentially causing the same physiological traits as someone who has sickle-cell anemia. Favism does provide protection from malaria, as does sickle-cell anemia. People susceptible to favism often react very negatively, even fatally so, to anti-malaria drugs. You are most likely to have Favism if you have ancestors from malaria prone areas such as the Mediterranean. * Birds have nucleated red blood cells, unlike mammals. I suspect that would affect their likelihood of suffering from favism but I have been unable to find any primary literature on the subject so far. At the moment I would consider it safe to feed your birds fava beans in small amounts, but still be vigilant for any odd behaviors or change in their stool after eaten fava beans* 


These are either long beans or runner beans I didn’t check when I took the picture.

Can only eat immature beans/pods

 There are some species that are edible when the pod is young and tender and become toxic as they mature. I don’t have personal experience with these kind of beans, if you eat or grow a bean like this let me know and I will add it to the list.

Moonshadow hyacinth bean, red leaved hyacinth bean (Dolichos lablab)


  Dry legumes that are safe to eat when sprouted

 Lentils    (Lens culinaris)

 Mung Beans  (Vigna radiata

Adzuki  (Vigna angularis

 Chick Peas   
A.K.A. garbanzo beans  (Cicer arietinum

 Peas   (Pisum sativum)


How to sprout:

In order for legumes to be edible raw they, need to soak, at minimum, overnight. As the seed hydrates  it becomes enzymatically active; breaking down lectins, enzyme inhibitors and complex sugars as the seed starts to sprout. When you can see a tail, the radical, you know the seed is active and growing so it has probably ( if it’s one of the safe five for sprouting anyway) deactivated most of the harmful compounds. 

You will need a container that is at least three times as large as the amount of dry legumes you start with. Before sprouting, or cooking for that matter, you need to look over the beans for nasty ones, dried out shriveled ones that will never be tender and rocks or other foreign objects that might be in the mix. Then rinse them vigorously with cold water, drain, and fill the container with more cold water. It’s best if you can change the water while soaking. It moves the beans around, keeping them from getting compacted and hard to get out later. It can also keep whatever you are sprouting from souring in hot weather and potentially could help get more harmful compounds out faster. 

After the overnight soak you can keep the little guys around for quite a while if you treat them carefully. You should rinse them as often as possible and keep them in a normally lighted area. Not in hot sun or dark shade, since either can make the sprouts mold and or die. Make sure they have good airflow and are drained well between rinses. There are these nifty mesh lids you can buy and even whole little gadgets for sprouting. Or, you can use bowls, mason jars and mesh colander like I do and not buy anything but the beans! At minimum you should rinse two or three times a day. People add all sorts of things to the sprouting and rinsing water. I don’t think any of that is necessary and more likely that it could cause harm than anything. What you might add could leave potentially harmful residue or encouraging microbial growth by inhibiting sprouting or harming the sprouts. If you simply practice good sprouting technique and keep an eye out for mold or any other spoilage- use your nose here folks!- I think you will have the best results.

Maybe you are wondering what the heck anyone does with bean sprouts? well, if you haven’t tried them you are missing out! They are yummy in stir-fries, salads and I have this crazy Lentil Cake recipe that’s made with sprouted lentils and mung beans.  * you could totally make these for your birds just leave out the salt, garlic, onions or any other onion family ingredients and cook them in a dry pan or with a very small amount of bird safe oil.  My cockatiels like them and it’s not hard to take out a little to cook for them before you add the human ingredients.*

I hope this post was informative and if there’s anything I missed or you think I should add; please let me know!

What’s your favorite way to eat legumes? 

This post is participating in the Frugal Days, Sustainable Ways #82 Blog Hop , 122nd Homestead Blog Hop, HomeAcre Hop, Real Food Wednesdays From The Farm and Healthy Tuesdays, head on over to find other great blogs like ours!

Categories: Uncategorized


Anonymous · July 25, 2013 at 4:48 pm

Naive is right. Never knew there was so much involved with legumes. Thanks.

Emily Swezey · July 25, 2013 at 8:52 pm

I know, who would have thought? When you cook them right they actually taste better, if you can believe that, and they cook faster so it ends up being a win win all the way around. Thanks for visiting and commenting, Come again soon!

Lisa Lynn · September 4, 2013 at 1:28 pm

Good info! Thanks for sharing on The HomeAcre Hop!

Anonymous · January 20, 2014 at 6:44 pm

how long must you cook sprouted lentils to make them safe and at what temperatures, or if for eating raw how many days for them to not have too many lectins

    Emily Swezey · January 20, 2014 at 7:40 pm

    Hi there, thanks for visiting and commenting! I think it might be good for you to read the article over again or if English is your second language, put the post through a translator. When you read the post again you will see that lentils are one of the “safe five” meaning they are safe to eat without cooking if properly sprouted. As for your second question, opinions vary on that topic. There’s a camp that says it best to eat them BEFORE a tail shows, then there’s the other camp- that I’m in- that believes its best to wait until you can see the tail aka radical or seed root. Let me know if you have any more questions.

DeAsUnJa · January 17, 2017 at 12:08 pm

Hi, Does anyone know if Tepary and Pima Lima Beans are safe to sprout and feed to chickens? And how do you know?
Thank you,

    noahkids@hotmail.com · January 18, 2017 at 6:42 pm

    Look through the article for the section that says “Dry legumes that must be cooked”, both lima and tepary beans are listed in that section. Regardless of the species you are feeding them to they must be cooked, not just sprouted. For more information read the links included above.

Selma glunn · January 30, 2018 at 9:40 pm

I get blotted and very gassy even eating beans sprouted,,,why?

Jill · April 12, 2018 at 6:58 pm

I bought organic black beans I soaked a pound in water covered 3 inches above for 48 hours loosely covered on the counter. I changed the water twice. I still see no tail or sprouting. What am I doing wrong?! I did the same for organic split peas.

I have an Instant Pot. I was hoping to boil the beans for at least 15 mins, then cook them thoroughly in my Instant Pot.

Leave a Reply

Your email address will not be published. Required fields are marked *