I think it’s a matter of how much nutritional value the food conveys untreated vs. treated and whether it is a staple in one’s diet. The treated corn flour used to make tortillas does provide more nutrition in the form of vitamins, minerals, and protein which would otherwise just pass through the gut. Malnutrition can occur if all one eats is corn. The Indians learned to soak corn in alkali water to make hominy and and then ground to make a paste or dried into a flour. Tortillas are made with a treated flour called Masa Harina.