Can it be true? After all, chilli con carne just wouldn't be the same without red kidney beans. Are they really poisonous? In their raw state, they do contain toxins that make them unsuitable for consumption. Eating raw or inadequately cooked beans can lead to symptoms that indicate food poisoning. Vomiting and diarrhoea may occur two to three hours after consumption. When non-organism poisoning is to blame, high concentrations of the protein haemagglutinin are involved. The toxicity of raw red kidney beans is related to their levels of haemagglutinin - around 37,000 to 53,000 units per gram in their dry state. However, when the beans are soaked for 18 hours, between 22 to 66 per cent of the protein is removed.
Haemagglutinin is therefore destroyed by traditional cooking methods (soaking, then boiling). Kidney beans in a can have been through a rigorous heat process, and are fine to eat immediately, though detailed understanding of their toxicological properties is still limited.