Fundamentally, We consider as Useful Foods those that still stay with life and can reproduce it. In the case that the food does not contain the seed, it is always taken as a Useful Food if their cells are latent and are living.
This is the case of eatable vegetables, fungi and fruits in raw state.
Nevertheless, when we cook foods that are alive (or raw), their cells die and lose most of their nutritional virtues.
On the contrary, there are some foods that never must be raw eaten , instead they must be cooked. As
is in the case of the eggs, the yucca, the potatoes. From them, their
mineral components are taken as nutrients
You can find more suggestions of Useful Foods on page: