Kidney bean poisoning can occur if the beans are not properly cooked.
Raw kidney beans contain a toxic level of phytohemagglutinin that can cause food poisoning symptoms if ingested in significant amounts.
By the end of this short post, you’ll know why kidney beans can make you sick, and what to do to prevent health issues.
Table of Contents
How Do Kidney Beans Cause Food Poisoning?
Lectins are found in all sorts of food, and are fine to ingest in small doses.
But certain lectins like phytohemagglutinin can act as a toxin and cause health problems if consumed in large amounts.
It turns out that raw red kidney beans contain a very high level of phytohemagglutinin. It functions as the plant’s natural deterrent against pests and pathogens.
The good news is that phytohemagglutinin can be destroyed with sufficient heat. Boiling red kidney beans for at least 10 minutes at 100 degrees Celsius is known to completely destroy this lectin.
White vs Red Kidney Beans
While white and red kidney beans are very similar, they have very different levels of this toxin.
Red kidney beans typically have 25,000-70,000 micrograms of phytohemagglutinin per gram of bean, while white kidney beans only have 5-10% of that number.
Note that when red kidney beans are cooked correctly, there is roughly 200-400 mcg/g leftover, which is a safe amount.
Preventing Kidney Bean Poisoning
As mentioned, the only way to prevent food poisoning from red kidney beans is to cook them properly.
This includes:
- Soaking dry beans for at least 5 hours (overnight is fine)
- Draining the soaking water and rinsing the beans
- Cooking them in boiling water for at least 10 minutes (although it takes much longer to cook them fully, but you can reduce the temperature after 10 minutes if desired)
Note that even though slow cookers kill a lot of bacteria, most slow cookers will not get hot enough to destroy phytohemagglutinin, so they should not be used to cook red kidney beans.
Can Other Cooking Methods Be Used?
One study found that stir frying red kidney beans for more than 18 minutes, or braising them for more than 10 minutes effectively removed the toxin.
The cooking temperature is the most important factor, not necessarily the cooking method.
Symptoms of Kidney Bean Poisoning
Ingesting just 4 or 5 raw kidney beans can lead to significant poisoning symptoms.
If cooked incorrectly, symptoms usually appear within 1-3 hours of consumption and include:
- Nausea
- Vomiting
- Diarrhea
- Abdominal pain
While there are no recorded deaths from kidney bean poisoning in medical journals, severe cases may require hospitalization.
Treatment of Kidney Bean Food Poisoning
There’s no treatment for food poisoning caused by improperly cooked kidney beans that can be administered at home. If someone suffers from diarrhea, extra hydration may help.
If symptoms are severe enough to require treatment, it should be decided upon and provided by medical professionals at a hospital.
Can Canned Kidney Beans Be Toxic?
Canned kidney beans can certainly go bad (although it takes a very long time), but all canned kidney beans have already been cooked at an appropriate temperature.
Unless you get a “bad” can of kidney beans, there’s no reason to suspect that they are the cause of any food poisoning symptoms.
Summary of Kidney Bean Poisoning
Raw red kidney beans contain a toxin called phytohemagglutinin that must be destroyed with high temperature cooking before the beans are eaten.
If consumed in significant amounts, it will lead to food poisoning symptoms like nausea, vomiting, and diarrhea.
Most cases resolve themselves, but a small percentage may require hospital attention.
