It may lead to poisoning if beans are not cooked.
Raw beans contain a toxic protein, called agglutinin, which can agglutinate blood cells. If beans are kept for too long, a large amount of nitrite may be produced, which may cause denatured hemoglobin. Nitrite can be decomposed and destroyed in high temperature. If you eat half cooked beans, you may be poisoned.
Uncooked beans can form a material enzyme, which can cause a series of poisoning symptoms. Weak limbs and dizziness in the mild cases, nausea, vomiting, diarrhea in the severe cases, and even froth and spasm in the mouth.