Yes, Uncooked Kidney Beans Can Be Toxic — Here's How To Prepare Them Safely
Just say "no" to slow cooker chili. It may sound like a great weeknight dinner — throw a few things in the pot, hit the switch, and head off to your day. Not so much, as it turns out, at least if you're using dried beans. Cooked wrong, red kidney beans can cause toxic lectin poisoning. The offending protein, called phytohaemagglutinin, is considered a major risk in red kidney beans soaked from dry. According to the FDA's Bad Bug Book, phytohaemagglutinin poisoning can cause nausea, vomiting, and diarrhea. The scariest part? All it takes is four or five beans! The illness only lasts a few hours, but the FDA says diarrhea can follow later even after the three hour nausea and vomiting window. Fortunately, it's easily preventable, so don't ditch all your bean-based recipes just yet.
And it's not just kidney beans — while all plants and some animals (even humans) contain some level of lectin, cannellini beans (aka white kidney beans) and black or turtle beans also contain higher levels of phytohaemagglutinin (via Ohio State University and the University of Illinois Extension). Additionally, broad or fava beans, "navy, pinto, lima ... wax, jack, string, and field beans" all contain varying lectin levels and shouldn't be eaten raw, according to For the Birds. While it's unlikely that improperly cooked cannellini beans on their own will make you sick, something like three-bean chili should probably be approached with caution — or with cans.
Not so cool beans: high heat is essential
According to the FDA, all it takes to safely prepare dried kidney beans (or any of those listed above) is to soak the beans in water for 5 hours and bring them to a boil for at least 30 minutes. Avoid the temptation to use the soaking water for boiling — it could make you sick! The FDA recommends dumping that water and boiling some fresh. Harvard's School of Public Health even recommends draining and thoroughly rinsing the boiled beans to be sure any denatured toxic proteins are removed. However, since the toxin is destroyed by heat, this is just to be extra safe. While many say cooking for 10 minutes is long enough, a 2020 outbreak in Denmark that sickened 45 was traced back to beans that were only cooked for 10 to 15 minutes (via Food Safety News).
If you're thinking about adding some easy baked beans as a summer BBQ side, baking is perfectly safe. Whatever the cooking method, the temperature must reach at least 212 F. Slow cookers just don't get hot enough to break down the toxic proteins. Store-bought canned beans, on the other hand, are perfectly safe, so you can feel good about throwing a quick Taco Bell copycat bean burrito in the microwave (via University of Illinois Extension). It may sound scary, but kidney bean poisoning can be easily avoided with little-to-no prep work. Just remember to keep your dried beans clear of the slow cooker.