Also, even if you did follow indegenous preparation methods, the food industry may have changed the plant by artificial selection or genetic modification such that the indegenous preparation is not as effective, so you're better off ditching them anyway.
Vegetables have significant phytotoxin content without significant nutrient content, specially in forms bioavailable to us (eg. a lot of carotinoids in carrots, except we are terrible at converting that to Vitamin A... we need the retinol form, readily available in milk, eggs, fish, meat etc.).
Plants are living beings and don't want to be eaten. They can't fight or flight so their defense is toxins. We have domesticated some of the plants and learnt how to remove those toxins over thousands of years... but if you don't know how to do that effectively, you're better off not eating them.
