Some cacti are poisonous and not edible; edible cacti are non-toxic. There are many varieties of cacti, some are poisonous and some are not. Poisonous cacti mainly contain more alkaloids and other ingredients, which are irritating to the gastrointestinal tract and the mucous membranes of the skin. There are relatively few varieties of non-toxic cacti, so you need to pick them carefully. In some countries of the world, such as the Mexican region, cacti have been selected and bred for use as food. Cactus is very rich in dietary fiber. Dietary fiber retains water in the stool, increases stool volume and promotes intestinal peristalsis, making it a very good food for constipated people. The best way to consume cactus is to soak it in lightly salted water for 10 to 15 minutes while the outer skin is thoroughly removed. The purpose of soaking is to remove the alkaloids from it, which are soluble in water. If you experience any discomfort such as abdominal pain or diarrhea from consuming cactus, seek medical attention from a doctor.