"Less than half a dozen kidney beans (phaseolus vulgaris) can make you as sick as a parrot. Surprised? Well, you would be, seeing that you’ve probably had nearly as many chilli con carnes as you’ve had hot dinners with no ill effects … apart from maybe a bit of wind. But don’t be fooled – those innocent looking red beans harbour the potential for hours of torture. The evil force within them are lectins, also called phytohaemagglutinins, a type of protein found in many types of beans. Kidney beans have the highest concentration of lectins.
Why are lectins so terrible? For two main reasons: they bind to intestinal cells preventing nutrient absorption and, when they enter the blood stream, they also bind to red blood cells. This causes the red blood cells to clump together, a process referred to as “agglutination”, rendering them useless. Symptoms of “red kidney bean poisoning” occur 1-3 hours after consumption, entailing extreme nausea, severe vomiting, followed by diarrhoea and abdominal pain. Recovery is usually rapid, and sets in after 3-4 hours.
You’re probably still wondering why this has never happened to you. The answer is simple: lectins are inactivated during cooking. Tinned kidney beans are always cooked, and when buying them dried, they are soaked and boiled before eating. It takes only four to five raw kidney beans to trigger symptoms – and, paradoxically, undercooked beans are worse than raw beans. You should, for example, never use dried or raw beans in a slow cooker, which cooks foods at low temperatures over extended time periods. Heating kidney beans to only 80°C (i.e. below boiling point) can turn them five times more toxic. To be on the safe side, you should soak dried kidney beans in water for at least 5 hours, pour away the water, and then boil them for at least one hour in fresh water. Raw beans need to be boiled for a minimum of ten minutes. Even green beans, such as French or runner beans, contain a small amount of lectins and should not be eaten raw.
The good news is that there is some interesting research going on in trying to find medical applications for lectins. Two promising areas are HIV and cancer, for which the selective toxicity of lectins may be harnessed."
Good information. I never knew they could make you that sick. I hope you feel better though :(
This information will help to lead a better sound life. I think I have to be very careful about eating beans.