Why You Should Cook Your Beans To Avoid Food Poisoning

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red white kidney beans

Red & white kidney beans contain a toxin and should be cooked to 100C.

Beans are of course, a very healthy food that are high in protein and contain almost all essential amino acids. Eating beans regularly could help to prevent a variety of health conditions including Type 2 diabetes, colon cancer and heart disease. With their high fiber content, they also are a great food for hunger reduction if you are overweight and need to lose some.  Being low in calories and with zero cholesterol, beans have been a mainstay in many diets around the world.

However, you might want to be cautious about eating raw beans.  Some varieties including red and white kidney beans contain a toxin called phytohemagglutinin or PHA for short. If you’ve never seen that word before, you are probably wondering what in the world it is!

Phytohemagglutinin, a natural insecticide, is a carbohydrate binding protein and can have toxic effects in high doses, but is safe in low doses and is actually used in some medical studies. However, in high doses such as found in raw beans, it can cause illness with the symptoms of nausea, vomiting, abdominal pain and diarrhea. As few as five raw kidney beans can cause this food poisoning.

Usually, the symptoms will disappear within 6 to 24 hours and medical attention is not required. However, if you do have the symptoms, you should consider medical attention in order to rule out any other bacterial food poisoning that you may have.

Cooking kidney beans will reduce the amount of PHA in the beans to non toxic levels if the beans are cooked at 100C (212F) for at least ten minutes.  If you plan on cooking your beans in a slow cooker, you should heat them to the boiling point of water first for the ten minutes, before putting them in the slow cooker.  Heating beans in slow cookers without cooking them to 100C can actually increase the levels of phytohemagglutinin above what they are in the beans in their raw state.

Canned beans are already cooked and don’t need to be reheated to boiling point, however dried beans that have been rehydrated  should be cooked at 100C for ten minutes before being consumed.

The beans with the highest levels of PHA include red kidney beans (extremely high levels), white kidney beans, lima beans, and fava beans. In addition, lima beans contain another toxic substance called cyanogen. Cyanogen is also reduced to safe levels with cooking at 100C.

So, while beans are very healthy for you, be sure to fully cook them to enjoy their health benefits.


Health Benefits of Beans



Phytohemagglutinin derived from red kidney bean (Phaseolus vulgaris) (PubMed)

Phytohemagglutinin on the lima bean (Phaseolus lunatus). Isolation, characterization, and interaction with type A blood-group substance.


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  1. Les Clayton on December 16, 2012 at 11:15 am

    I had never heard of this before! I do eat a lot of beans, especially kidney beans in chili. I also use dried beans but I heat them to boiling point for quite a while after I’ve softened them by soaking them in water.

    Good to know!

  2. Liz MacLean on December 17, 2012 at 12:28 am

    So let me get this straight, if I only cook the beans until they are soft and edible but don’t boil them, they could be toxic? I have never heard of that. I need to tell my mom about this as she is feeding us beans all the time.

    • admin on December 17, 2012 at 3:40 am

      Hey Liz, thanks for your comment. Yes it is true, and especially so with red kidney beans which have the highest levels. I know it seems odd – but the research shows it!

      • Liz MacLean on December 17, 2012 at 4:48 am

        Thanks.. yeah.. my mom says she does them in a pressure cooker to soften them up. I guess I should pay more attention and learn some things :).

  3. Adalberto Capp on May 23, 2013 at 3:58 am

    Kidney red beans are commonly used in chili soup chili con carne and are an integral part of the cuisine in northern regions of India. Red kidney beans are used in New Orleans and much of southern Louisiana for the classic Monday Creole dish of red beans and rice. The smaller, darker red beans are also used, particularly in Louisiana families with a recent Caribbean heritage. Small kidney beans used in La Rioja, Spain, are called caparrones.^-,’

  4. Jill Hughes on July 30, 2013 at 6:02 pm

    Thank you so much for clearing this up about the possibility of food poisoning in lima beans. I had heard a rumor about this and really wanted to check it out. Good to know that cooking the beans will remove the toxics from them.

    I pretty much only eat the canned ones anyhow, and they are cooked so that means there is nothing at all to be worried about, right? I wonder what else we might not know about naturally occuring toxics in some foods!

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