Kidney bean poisoning

Kidney bean poisoning |

You hear about poisonous mushrooms and berries and all that jazz, but kidney beans? Yes, as it turns out. Raw kidney beans contain very high levels of phytohaemagglutinin, a protein that wreaks havoc on cell walls and cell metabolism.

But wait! Proteins don’t do well at high temperatures, so boiling the beans for 10 minutes will break down the harmful molecule and leave you with perfectly safe beans. This means that canned beans are fine, as are dry beans that you simmer on the stovetop. In a slow cooker, though, the beans never hit boiling (they hover around 180 degrees F, water boils at 212 degrees F), the protein stays intact, and it can lead to some really unpleasant consequences.

Kidney bean poisoning |

The protein itself! This shows us the general shape of the protein, and the thick lines indicate some of the internal structure. Image from the RCSB Protein Data Bank.

The sickness comes quickly, bringing severe nausea, vomiting, diarrhea, and stomach pain within a few hours of eating the undercooked beans. Some people wind up in the hospital for fluids, but the symptoms go away on their own after about 4 hours. A really, really bad 4 hours, yes, but it’s not going to do any permanent damage (other than to your opinion of kidney beans).

So let’s be sure to give those beans a good boil before throwing them in the slow cooker. And if you need an excuse to do just that, check out the recipe that brought all of this to my attention–delicious and easy slow cooker dal makhani.

For more on kidney bean toxin, check out the FDA’s synopsis and an article from Livestrong.