Important Info for Cooking Dried Beans in a Crock Pot or Slow Cooker

This post may contain affiliate links which means I get commissions for purchases. Sponsored posts will always be clearly disclosed. Privacy Policy

Yesterday when I wrote the post on how to cook with dried beans, I had that nagging feeling, you know the one that says I was forgetting something important. It turns out I was, I edited it into yesterday’s post, but I wanted to be sure everyone saw the update.

Unless you are willing to boil soaked, red kidney beans for 10 minutes prior to placing in the slow cooker or Crock Pot™ in fresh water, it’s best to just use the stove. Kidney beans contain a toxin called Phytohaemagglutinin, add that to your spelling list, kids. Other beans such as white kidney contain the same toxin, but in lesser amounts.

So what does this phyto-whatchmacallit toxin do? Is it like the “toxins”-scare quotes, FTW!- you supposedly lose when fasting or sweating?

Not quite. Phytohaemaggglutinin causes severe gastric distress.

Read that as: You won’t know which way to face the toilet. That’s not a happy feeling folks. Avoid it.

How do people come in contact with this bug?

Sometimes people try using raw, soaked kidney beans in salads like 3 bean salad. The high temperature of the canning process is enough to destroy the toxin which is why commercially canned 3 Bean Salad isn’t a risk.

Other times people consume partially cooked red kidney beans, which is far worse. There is an interesting phenomena with phytohaemagglutinin and slow cookers / Crock Pots™. The potency of the toxin in kidney beans can actually increase by 5x if the beans are heated only to 80°C or 176°F¹. When you simmer on the stove, the temperature is 185°F – 205°F or 85°C – 96°C and it’s quite easy to turn the stove up a little for ten minutes after the beans have begun to soften.

If you must use your slow cooker, adjust the recipe to accommodate canned or thoroughly cooked kidney beans.

The FDA recommends:

Soaking for at least 5 hours, discarding the water, and boiling in fresh, clean water for at least 10 minutes, before using a slow cooker.

FYI: The toxin is also found white kidney beans at about 1/3rd the concentration and broad beans at about 5 to 10%. Use your common sense with these beans, too.

The literature I read only mentioned a few outbreaks in the late 70s in the UK and only anecdotal evidence in the US. But keep this in mind.  Most people in gastric distress wait a day before going to the doctor -who really couldn’t do much except administer fluids and run up large bills with testing. Typically the effects of the toxin typically clear up in 3 to 4 hours after the symptoms start, which start 1 – 3 hours after eating. It is likely that accidental poisonings happen and are under-reported due to blame on the stomach flu or “it’s just a bug.”

Remember this bug is avoidable.

My work here is done.

Keep calm and carry on.

Send your domestic questions to


¹FTW, for those who don’t immerse themselves in Internet culture means For the Win. My ex-husband is prior service, he was in the Navy and they had the initials FTN on many things. It wasn’t a happy phrase, (expletive deleted) the Navy. I thought FTW meant (expletive) the world. “It’s 5 o’clock, I’m clocking out and going home, FTW!” has very different meanings, depending on the interpretation you use. I was very relieved when I learned the actual acronym, people weren’t half as bitter as I thought.

²Reference: Bad Bug Book Foodborne Pathogenic Microorganisms and Natural Toxins Handbook Phytohaemagglutinin

³Image Credit RoccoMichele

Print Friendly, PDF & Email

Sharing is caring!

15 thoughts on “Important Info for Cooking Dried Beans in a Crock Pot or Slow Cooker”

  1. I was hoping you’d add something about kidney beans, but as it’s you were talking about here, I had faith you would. I once had the misfortune of having to tell a friend that she should have cooked her kidney beans, and that it was going to get worse before it got better. It wasn’t purty. It boggles my mind that this isn’t that well-known as a food fact.

  2. I have never heard of this. I did make some kidney beans awhile back, but on the stove, thankfully.

    I read recently that there is just no such thing as a "24-hour flu" or a short-term bug, less than a day long. That's all food poisoning of one sort or another.

    Your comment about FTW was funny. I've seen that but didn't know what it meant.

  3. I do believe I'll be pitching the kidney beans that are in the freezer!

    I too had no idea what FTW meant, but all my cynical attempts to decipher it started with {not for}.

  4. Apparently, if you heat water in a slow cooker on low, it should eventually (in a few hours) reach 185°F. Cooking beans in a slow cooker on *high* for a long time would certainly raise the temperature of the beans far above 176°F. I'm guessing that there's really no risk if kidney beans are in a slow cooker on high for a very long time, but it would be nice to see something more authoritative about this.

      • With the cooker on high, the water should reach 212 degrees or very close to it (depending on altitude) within a few hours. I find it hard to believe that beans in a slow cooker set to high would be below 200 degrees after 3 or 4 hours.

        I've previously looked at the page that you linked to. The cited cases of illness were with beans in a casserole in a slow cooker set to low. This situation is completely different from beans in water in a slow cooker set to high.

        There really don't seem to be good studies about these issues, but I don't see much justification for much worry. If you use kidney beans in a slow cooker, just make sure to use the high setting, and don't take the lid off during the first 5 hours or so of cooking.

  5. Thanks for the important info. I would have appreciated the FTW explanation in parentheses right after it, though, and I still couldn’t quite figure out the “toxins”-scare quote stuff. What is that about anyway?

  6. Hi 🙂 When I cook kidney beans, and all other beans, I soak them for 24 hours, then crock pot them on low for another 24 hours. By the end of the cooking they have reached a boil for a while (is that why I keep killing my crock pots?) I’ve never had gastric problems from them, however they are definitely cooked and then some. The reason I do this is because I’ve read about an acid in legumes that stops the body from being able to absorb iron. The only way to destroy this acid is long soaking and long slow cooking. Or fermenting. Soybeans are the exception- no amount of soaking and cooking destroys the acid in soybeans. Fermenting will destroy it, tho (soy sauce).

    I’ve come across this information about toxic kidney beans before, in a murder mystery book. Fiction.

    • While I wouldn’t regard everything that comes from a fictional source as the truth, the best fiction weaves in truthful elements. That said the information comes from the FDA you can choose to call that fact or fiction… Your long cook time in new crock pots is what has likely kept you out of the bathroom for extended periods. 🙂

  7. I have cooked red kidney beans for many years with out getting the shits. I cook mine in a slow cooker for 8 hours with chicken. I set my slow cooker on automatic. Use common sense, most people don’t have that.

  8. How funny–I just made a 15 bean soup using the instructions from the provider for a slow cooker. I think maybe since it cooks so long (8 hrs on low) it was ok. I actually accidentally soaked the beans for 8 hours before I cooked them and drained them really well too. I’ll stick to the stove top version for next time.


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.